This PDF file contains the front matter associated with SPIE Proceedings Volume 10098, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and Conference Committee listing.

Invited presentation by Prof. B. Witzingmann The development of supercontinuum sources is advancing fast in the last decades. As do all nonlinear effects, the supercontinuum generation strongly relies on the nonlinearity of the active material. This nonlinearity may be greatly enhanced in specially designed photonic-crystal fibers, making supercontinuum sources widely available. Nevertheless, pulsed lasers are required to supply high enough field strengths to overcome the threshold for supercontinuum generation. We study a new cluster based class of nonlinear media that exhibits ultra-low thresholds for supercontinuum generations, thus enabling the use of a low coast steady-state laser diode as the driving laser [1]. The clusters are composed of a tin sulfide based core that is surrounded by four organic ligands. The core adopts an adamantane-like architecture, [Sn4S6]. It has a tetrahedral shape and thus lacks inversion symmetry, enabling nonlinear processes. The four ligands (R = 4-(CH2=CH)-C6H4) are consolidating the structure of the core. Yet, as they are randomly oriented around the Sn-C bonds, they are also preventing any long-range order in the solid phase of the compound. As a result, the compound is obtained as a white powder with totally frustrated order. This powder has been studied in respect to its optical properties. When irradiated with a continuous-wave infrared laser of sufficient intensity it emits a warm white spectrum that is virtually independent from the pump-wavelength in a range of 725-1050 nm. Lowering the pump intensity, however, changes the spectral weight to the red, similar to dimming of thermal emitters. The input-output characteristics, however, exclude a thermal process as the source of the observed white-light. Additionally semi-classical calculations of the white-light generation process are performed, underlining this statement. [1] Rosemann N.W., et al.; Science, 2016, 352, 1301-1304

Nanophotonic modulators and photodetectors are key building blocks for high-speed optical interconnects in datacom and telecom networks. Besides power efficiency and high electro-optic bandwidth, ultra-compact footprint and scalable co-integration with electronic circuitry are indispensable for highly scalable communication systems. In this paper, we give an overview on our recent progress in exploring nanophotonic modulators and photodetectors that combine the specific strengths of silicon photonic and plasmonic device concepts with hybrid integration approaches. Our work comprises electro-optic modulators that exploit silicon-organic hybrid (SOH) and plasmonic-organic hybrid (POH) integration to enable unprecedented energy efficiency and transmission speed, as well as waveguide-based plasmonic internal photo-emission detectors (PIPED) with record-high sensitivities and bandwidths.

Carrier distribution of semiconductors (SCs) differs from metals where they can give inhomogeneous carrier distributions like the classical Schottky junction. In this study, we show that the carrier distribution at a moderately doped semiconductor – dielectric (DE) interface can be tuned by applying external voltage, and then an inhomogeneous permittivity. Using the Maxwell’s equations for doped semiconductor surfaces, we illustrate the voltage controlled tunability of plasmon and phonon polaritons.

We theoretically study the nonlinear dynamics of silicon ring cavities with active carrier removal. In this system, linear dispersion, Kerr nonlinearity, two-photon absorption, and free-carrier dispersion / absorption play a key role in the dynamics and the steady-state behavior of the device. Placing the cavity inside a reverse-biased p-i-n junction allows one to reach a regime where both optical bistability and limit-cycle oscillations are accessible. Based on these phenomena, we propose and simulate a free-carrier based random number generator and an "Ising machine", consisting of interconnected ring cavities, which searches for the ground state of the NP-hard Ising XY problem.

Publisher’s Note: This paper, originally published on 22 February 2017, was withdrawn per author request.

The effect of group-velocity dispersion (GVD) and self-phase modulation (SPM) on the coherent pulse progression in mid-infrared (MIR) quantum-cascade lasers (QCLs) is investigated. The background saturable absorber (SA) effect is included in the study. In this case, the lasing pulses can be built up from the instable continuous wave (CW) operation condition related to both SA effect and GVD under the influence of a small initial disturbance. The theoretical model is built based on the Maxwell-Bloch formulism accounting for the couplings among the electric field, the polarization, and the population inversion. The pulse evolution in time-spatial domains is simulated by the finite difference method with prior nondimensionalization, which is necessary for convergent solution. We first studied the QCLs with ring cavity to illustrate the interplay between GVD and SPM effects. It is found that the anomalous GVD, which receives less attention in the study of QCL dynamics, can significantly narrow the spectrum splitting between side modes. The SPM can broaden the linewidth of the spectral modes. Their combined effects can lead the possibility of forming solitons. We also extended our study to the same QCL medium with a Fabry-Perot (FP) cavity. The additional effect of spatial-hole burning (SHB) is identified in results obtained.

Optical sources for the forthcoming terabit/s era of optical communications and networking will require multiple frequency-locked carriers, each with low phase noise, in order to minimize the spectral occupancy of the overall channel bandwidth. One method to construct a highly reconfigurable version of such a source is to use an optical frequency comb from a gain-switched laser to simultaneously injection-lock many different single mode lasers. The outputs from the single-mode lasers are all mutually frequency locked and possess the same low-phase noise properties of the gainswitched comb. In this submission, we present numerical simulation results from the entire system of simultaneously injection-locked single mode lasers by firstly simulating an optical frequency comb from the gain-switched laser and then using that frequency comb to injection lock the single-mode lasers. The simulation approach is to use lumped rate equations with the appropriate stochastic Langevin terms for spontaneous carrier recombination and for spontaneous emission. The inclusion of the stochastic terms are vital when identifying the locked states of the entire system. Using the simulator we are able to identify important criteria to maximize the frequency locking range that suppresses the cross talk from adjacent comb lines to greater than 30 dB, and avoiding the carrier-photon resonance of the single mode lasers is vital to achieve this. The relative simplicity of the simulator has the advantage of being exploited within optical communication simulators to predict the communication system performance when using these sources, which would be of advantage to designers of such systems.

The dynamics of hybrid III-V/silicon Distributed Feedback (DFB) semiconductor lasers were studied under a combination of long and short feedback conditions. The allure of silicon photonics lies in the potential for production of low-cost, compact circuits that integrate photonics and microelectronics on a single Photonic Integrated Circuit (PIC)^1,2. It has been recently demonstrated that such tight integration of optical components increases the risk of short-cavity reflections within a PIC that can destabilize the laser³. Using novel III-V/Si DFB lasers, we simulated such reflections by coupling the laser using a cleaved fiber, thus creating a free-space cavity between the laser and the fiber tip. The sensitivity of such devices to this short feedback and its phase was then studied by comparing measurements performed with either a cleaved or a lensed anti-reflection-coated fiber, and revealed the modal and temporal dynamics created by the short-cavity feedback. A long fibered feedback cavity was then created within the experimental setup to study the route to chaos of the devices under long feedback, as well as the impact of the short feedback’s phase on this route. Due to a relatively high relaxation oscillation frequency of 15 GHz and the destabilization of the laser by both the short cavity and the long one; very wide chaos can be achieved when combining both types of feedbacks. This study thus reveals the impact parasitic reflections can have on a DFB laser’s characteristics in a PIC, as well as how these reflections can affect the dynamics of the laser in a well-known optical feedback scheme.

A quantum dot (QD) laser capable of two-state lasing in certain parameter regions is studied under external optical injection. Our modeling approach is based on microscopically based rate equations, which include carrier dependent index shifts obtained from a full Bloch-equation approach. Our results show an increase of the dynamical stability of the two-state QD laser under optical perturbations if compared to a single-state QD laser, e.g. to a QD laser with high losses in the excited state. Chaotic dynamics predicted for single-state QD lasers under strong and detuned injection completely vanishes if excited state lasing is possible. This suggests a general trend for semiconductor lasers to yield an improved stability against optical perturbations with more dynamical degrees of freedom.

Rate equations are derived for two lasers with a linear coupling element. A strategy and scheme is indicated for iterative self-consistent numerical solution of the steady-state equations. The presence of the linewidth-enhancement parameter is explicitly taken into account. Locking in stable operation for a large range of coupling phases is numerically demonstrated and locking ranges are given. Numerical and analytical results are given for the output powers and operation frequency as functions of the pump strengths of the individual lasers and their frequency detuning.

Large-signal analog modulation of a strongly injection-locked whistle-geometry semiconductor ring laser is investigated. Advantages of strong injection locking for high-fidelity large-signal modulation are confirmed through numerical modeling by comparing high-speed performance of a strongly injection-locked whistle-geometry semiconductor ring laser with that of a free-running ring laser.

In this proceeding we show how to formulate the quantum stochastic Schrodinger equation (QSSE) of the Jaynes-Cummings-model, where the cavity mode is subject to coherent feedback as control mechanism. We start from the Jaynes-Cummings Hamiltonian and the Hamiltonian for feedback on the cavity mode and derive the QSSE and show how to represent the system state as a matrix product state in order to derive a numerically tractable model for the case of the Jaynes-Cummings model subject to feedback. We compare the dynamics for stabilization of the Rabi oscillation with the solution of the Schrodinger equation in the single excitation regime. Furthermore, we compare this with the behavior for the case with two excitations in the system.

We investigate the spin transport properties of an isotropic quantum Heisenberg spin-chain. Driving the system out of equilibrium via two different reservoirs at the boundaries, the system exhibits negative differential conductivity for strong driving. We describe the system-reservoir interaction with a Lindblad approach. We show that the interplay between Lindblad dynamics and system dynamics influences highly the spin current. For weak driving, equal rates maximize the current while strong driving shows a counter intuitive behavior. Our findings could guide to an understanding of the transport properties which are dependent on the external driving.

Conventionally, theories of electromagnetic waves in a medium assume that only the energy of the field propagates in a transparent medium and the medium is left undisturbed. Consequently, the transport of mass density and the related kinetic and elastic energies of atoms is neglected. We have recently presented foundations of a covariant theory of light propagation in a medium by considering a light wave simultaneously with the dynamics of the medium atoms driven by optoelastic forces between the induced dipoles and the electromagnetic field. In the previously discussed mass-polariton (MP) quasiparticle approach, we considered the light pulse as an isolated coupled state between the photon and matter and showed that the momentum and the transferred mass of MP follow unambiguously from the Lorentz invariance and the fundamental conservation laws of nature. In the present work, we combine the electrodynamics of continuous media and elasticity theory to account for the space and time dependent dynamics of the light pulse and the associated mass and momentum distributions of the mass density wave (MDW). In this optoelastic continuum dynamics (OCD) approach, we obtain a numerically accurate solution of the Newtonian continuum dynamics of the medium when the light pulse is propagating in it. For an incoming Gaussian light pulse having total energy E₀ in vacuum, the OCD simulations of the light pulse propagating in a crystal having refractive index n give the same momentum p = nE₀/c and the transferred mass δm = (n²-1)E₀/c² as the MP quasiparticle approach. Since the elastic forces are included in our theory on equal footing with the optical forces, our theory also predicts how the mass and thermal equilibria are re-established by elastic waves.

Shuji Nakamura predicted in his Nobel lecture that GaN-based blue laser diodes are the future of solid state lighting. However, GaN-lasers still exhibit less than 40% electrical-to-optical power conversion efficiency while some blue LEDs exceed 80% and some GaAs-based infrared lasers exceed 70%. This talk investigates the reasons behind the efficiency limitation of GaN-based lasers and proposes an improved efficiency analysis method.

Using InGaAs/AlGaAs 1060nm commercial Laser Diodes (LDs) and Laser Diode Modules (LDMs) under high current (> 2A) and nanosecond pulsed conditions offers a large flexibility for fiber Laser seeding applications. Nevertheless, the behavior and long term reliability of these LDs under such conditions is not well established. Our work focuses on determining the reliability of 1060nm seed LDs under such conditions by the extraction of Electro-Optical (EO) characteristics and the monitoring of their evolution during pulsed ageing tests. In this context, two segments of parasitic oscillations (“A” and “B” type) were observed in the optical response of LDs and LDMs driven under such conditions, with their associated threshold current (I_thA and I_thB) on three batches of Laser diodes, with different packaging. We observed a strong part-to-part variation in the value of I_thA and a package dependency for I_thB. We conducted a near-field and a time spectral analysis of the LDs optical responses. A near field widening, associated with A-type oscillations, and a temporal spectral broadening, associated with A-type and B-type oscillations, were highlighted. Step-stress ageing tests were then carried out on two batches of three LDMs each, with different values of I_thA (3.9A, 7A and 11.2A for the first batch, 2.8A, 7.4A and 9.3A for the second). The modules with the lowest I_thA values were the first to fail suggesting this I_thA threshold as a key parameter for early failure detection. One module exhibited a gradual drop of the measured optical power. No variation of the optical power or of the I_thA and I_thB value were observed on the other modules, which were able to withstand the chosen ageing conditions without any noticeable decrease of their performances.

In this work we present an analysis of frequency response of Si-Si_0.12Ge_0.73Sn_0.15/Si_0.11Ge_0.73Sn_0.16 n-p-n mid-infrared transistor laser (TL) with strain balanced Ge_0.85Sn_0.15 quantum well (QW) in the base. The frequency response of TL for common base (CB) configuration is calculated from small signal relationship between the photon density (s(jω)) and emitter current density ( j_e(jΩ)) by solving laser rate equation and continuity equation considering the virtual states as a conversion mechanism. The intrinsic response of TL with and without quantum capture and escape effect of carriers on modulation bandwidth are also shown. Further, bandwidth of TL in CB configuration is obtained as ~4.5 GHz at 2 mA bias current with zero resonance and it increases with larger escape time and reduced capture time of carrier in QW.

Nitride-based ultraviolet (UV) emitters have attracted substantial attentions for various applications due to compact sizes and higher energy efficiencies. Despite the remarkable improvement in external quantum efficiency (ηEQE) for near- UV light-emitting diodes (LEDs), typical ηEQE for planar mid- and deep-UV LEDs is still low (<10%). One of the primary reasons for such low ηEQE is the strong anisotropic emission due to dominant transverse-magnetic (TM)- polarized output in high Al-content AlGaN quantum wells (QWs) while conventional planar LED structure favors extracting light traveling along c-axis. Here, we investigated the polarization dependence light extraction efficiency (ηextraction) of AlGaN-based flip-chip UV LEDs emitting at 230 nm and 280 nm with microdome-shaped patterning on sapphire based on three-dimensional (3D) finite-difference time-domain (FDTD) simulations. Our results show that microdome-shaped patterning on sapphire substrate is predominantly beneficial in enhancing TM-polarized output where up to 6.1-times and 2.4-times enhancement in TM-polarized ηextraction can be achieved for 230 nm and 280 nm flipchip UV LEDs with microdome-shaped patterned sapphire substrates respectively as compared to conventional flip-chip UV LEDs with flat sapphire substrates. In contrast, very minimal transverse-electric (TE)-polarized ηextraction enhancement (<1%) can be obtained from both 230 nm and 280 nm flip-chip UV LEDs with microdome-shaped patterned sapphire substrates. In particular, microdomes with diameter ≥ 200 nm for the investigated 280 nm UV LEDs are acting as reflector that severely limit light extraction through sapphire substrate. It is expected that this study will shed light on further optimizations of flip-chip UV LED designs for both deep-UV and mid-UV regimes.

Quadrant detectors (QD) are mainly used in research and industries for displacement measurement purposes due to their high sensitivity and accuracy as compared to other photodiode devices. Their scope extend to sub-nanometer scales and they are also operable at a wide temperature range with fast response frequencies, which make them the best candidate for beam displacement measurements. A growing interest in the field of optics are beams carrying orbital angular momentum (OAM), particularly Laguerre-Gaussian (LG) beams, due to their remarkable applications, which include optical tracking and gravitational wave detection. This study shows the combined effect of using different OAM modes of LG beam and varying angles of inclination of the QD on the sensitivity response and linearity index of the QD. In general, it was observed that a lower OAM value for the LG beam gives a higher sensitivity for the QD and a higher angle of inclination for the QD leads to a higher linearity index. This result gives a larger range of application for the QD.

We present a design technique addressing DBR fiber laser sensors. Modeling such lasers requires solving several critical simulation challenges. The laser cavity provides optical feedback where light experiences hundreds of round trips. The corresponding simulation schematic represents a network of elementary building blocks where the optical feedback introduces feedback loops requiring an iterative approach. We show how the cavity characteristics can be simulated in the frequency or time domain and compare their effectiveness. The design of digital filters accurately reproducing the grating spectra is one important challenge. For DBR lasers to oscillate in single mode the grating selectivity needs to be high enough, which may require a response length exceeding reasonable simulation windows by far. Furthermore, we discuss how to simulate the entire laser including an amplifying medium. We compare approaches using a system-level amplifier model, stationary and dynamic doped fiber models. We show that for an adequate description of the laser spectrum, modal and noise characteristics the time domain approach in combination with a dynamic fiber model is desirable. The frequency domain approach is problematic due to varying noise samples in each iteration. Note, due to the slow population dynamic in doped fibers tens or hundreds of thousands of iterations may be needed to achieve stationary operation. Once this is accomplished, the laser shows a single-mode spectrum with linewidth in agreement to the quantum limit. Using our developed model we show how the laser characteristics depend on the grating frequencies and can be used for sensor applications.

Multimode fibers are used extensively in many applications including optical illumination, sensing, imaging, and spectroscopy. Recently many optical MEMS applications reported the use of MM fiber for delivery of the optical beam to the MOEMS component to make use of its high throughput and thus higher power carrying capacity. In such applications, the spatial distribution and the spatial coherence of the output beam from the MM fiber affects greatly the performance especially if the beam is launched into an optical interferometer. In this work, we present a new model for the MM fiber output, in which the output beam is considered as a quasi-homogeneous shell source decomposed to its coherent elementary functions. Experimental results are obtained for multimode fibers with core/cladding dimensions of 62.5/125 μm, 200/220 μm and 400/440 μm and for different excitation conditions. The model shows very good agreement with the measured intensity distribution at different propagation distances.

Broad Area Semiconductor edge-emitting lasers typically display self-focusing nonlinearity due to the refractive index dependence on the population inversion. It induces the homogeneous solution instability, multi-transverse mode operation and filamentation. This behavior strongly deteriorates the beam quality and drastically reduces their applicability. We suppress this instability for semiconductors with small enough linewidth enhancement factors, αH, by the introduction of a single spatial modulation in the transverse and longitudinal directions. For large αH values, optimized multi-frequency spatial modulations are needed. The proposed scheme becomes especially interesting for high nonlinearities that correspond to the normal laser operation.

Directly modulated semiconductor lasers (DMLs) are important components as sources for short distance communication. In this paper, we present 1.3μm directly modulated lasers with high modulation bandwidth based on high-order slotted surface gratings. Such lasers are regrowth free, thus have the advantages of low cost and high reliability compared to the typical distributed feedback Bragg (DFB) lasers with buried gratings. The two dimensional (2D) scattering matrix method (SMM) combined with the time-domain travelling-wave model (TDTW) is employed for the analysis of the designed laser. By optimization of the grating parameters and cavity length, the slope efficiency about 0.35mW/mA and 3-dB-down frequency bandwidth higher than 41GHz have been achieved for a 250μm long high-order slotted surface grating laser.

The ability to create metamorphic hybrid heterostructure of 1300 nm spectral band VCSEL is demonstrated. Metamorphic semiconductor part of heterostructure with GaAs/AlGaAs DBR and InAlGaAs/InGaAs QW active region has been grown by molecular beam epitaxy (MBE) on GaAs (100). Top dielectric SiO₂/Ta₂O₅ DBR is made by the magnetron sputtering method. VCSEL has been studied under optical pumping (λ = 532 nm, diameter of the focused laser beam of ~ 1 μm) by using micro-PL setup in the range of optical pump power 0 – 70 mW at room temperature. Presence of the superlinear PL intensity growth having threshold-like dependence of PL integral intensity together with the PL peaks narrowing and mode composition modification with the pumping density increasing could be attributed to lasing behavior of the structure. Obtained results indicate the opportunity to use metamorphic growth on GaAs substrates for the 1300 nm range VCSEL manufacturing.

In quantum cascade lasers (QCLs), both the spectral gain characteristics and the nonlinear optical properties can be custom-tailored through quantum engineering. This enables mid-infrared and terahertz generation, and applications such as frequency combs. For the further development of QCL sources, suitable modeling approaches are required. Here we review various methods, ranging from semiclassical to quantum transport techniques. A focus will be on the adequate implementation of carrier-light interaction based on multi-domain simulation approaches to describe the actual lasing process and nonlinear optical effects. We demonstrate that by combining different models, we can exploit their corresponding strengths to significantly improve the performance of the simulation tool.

The design and optimization of realistically extended multi-quantum-well GaN-based light emitting diodes requires a quantitative understanding of the quantum mechanics-dominated carrier flow. Typical devices can be characterized by spatial regions of extremely high carrier densities such as n-GaN/p-GaN layers and quantum wells coupled to each other by tunneling and thermionic emission-based quantum transport. This work develops a multi-scale model that partitions the device into different spatial regions where the high carrier domains are treated as reservoirs in local equilibrium and serve as injectors and receptors of carriers into the neighboring reservoirs through tunneling and thermionic emission. The nonequilibrium Green's function (NEGF) formalism is used to compute the dynamics (states) and the kinetics (filling of states) in the entire extended complex device. The local density of states in the whole device is computed quantum mechanically within a multi-band tight binding Hamiltonian. The model results agree with experimental I-V curves quantitatively. Our results indicate tunneling to be a major contributor to the total charge current in LEDs.

In this paper, a new solution for the wave equation using the BPM technique is proposed. The basic idea of this new technique is based on reformulating the BPM equation to separate the real and imaginary parts and utilizes real system matrices only for the propagation steps. The updated equation exploits leap-frog method to couple the real and imaginary parts of the field at each propagation step. A comparison between the proposed method of solution and the conventional one is made and show that the proposed technique in solving the BPM equation get an accurate results with more time efficient way. Our method is proved to be at least 30% faster than the conventional BPM in solving waveguide problems. Such method can open the door towards efficient computational algorithms for solving complex systems.

Active media based on submonolayer (SML) quantum-dots are a novel gain material that potentially combines the high gain of semiconductor quantum-wells with the ultrafast gain recovery of Stranski-Krastanov quantumdots. By comparison of theory and experiment, we find an ultrafast gain recovery timescale well below one picosecond, along with a high optical gain. We investigate SML lasers theoretically and provide comparisons with conventional quantum-dot devices. We find a substantial increase in small-signal bandwidth and largesignal modulation capability. Our results show that semiconductor submonolayer laser and amplifier devices are promising candidates for high-speed optoelectronics as well as integrated photonics applications.

Optical injection into the ground state (GS) of a quantum dot laser nominally emitting from the excited state (ES) can induce a switch to GS emission. Antiphase oscillations are obtained consisting of short ES pulses with GS dropouts. These disappear when the master laser is sufficiently detuned or weak and CW emission from the (multimode) ES is regained. The pulses are accompanied by a notable expansion of the ES optical spectrum, which disappears abruptly when the system switches to the CW ES operation. The phenomenon arises due to the large difference in timescales between the ns scale pulses and the ps scale carrier distribution times of the quantum dots.

In this article, combined a multi-population rate equations (MPREs) of quantum dot lasers (QDLs) with an equivalent circuit simulation method of multi quantum well lasers, a multi-population quantum dot lasers equivalent circuit model (MPQDLs-ECM) is developed to simulate the lasing, temperature and the turn-on delay characteristics of the MPQDLs. Calculated results show that the QDs with different energy levels lase independently at low temperature but lase coherently at high temperature. Also, the GS and ES are observed to be in three different turn-on cases with the excitation from the low level to high level. All the calculations agree well with other reported experimental and theoretical results, indicating that the MPQDLs-ECM can be of great importance in simulating, analyzing, optimizing as well as predicting the characteristics of the QDs based devices.

Photonic devices and new functions based on HHI’s hybrid integration platform PolyBoard are presented providing lowloss thin-film-element-based light routing, an on-chip micro-optical bench and flexible chips comprising optical and electrical waveguides. The newly developed transfer and integration of graphene layers enables the fabrication of active optoelectronic devices in the intrinsically passive polymer waveguide networks with bandwidths in the GHz range. These novel functionalities in combination with the mature thermo-optic components of the PolyBoard platform such as tunable lasers, switches and variable attenuators pave the way towards new applications of photonic integrated circuits in communications and sensors.

In this paper, polymer optical waveguides (POWs), fabricated by using flexographic printing for printing conditioning lines onto polymethylmethacrylate (PMMA) foil substrate material and Aerosol Jet Printing for producing the core and cladding of the waveguide, are characterized by using Monte Carlo raytracing for the scattering process. This method offers the opportunity to simulate the propagation of light, which are traced through the produced POWs. In the first step, the surface roughness of all optical materials, which are involved in the fabrication process of the POWs, are measured. The roughness measurement of substrate, core and cladding material is necessary to interlink the surface roughness (Monte Carlo scattering model) with a non-sequential raytracing method. Not only the surface of each material is investigated, but also the roughness measurement of the interlayer between the printed core and cladding material is examined. To build up the complete manufacturing technology virtually, also the process parameters of the printing need to be investigated. The results of the tracing must be a value of the attenuation of a simulated printed POW to give the designer a feedback about the optical quality of the waveguide before the printing process. This project is part of the DFG (the German Research Foundation) founded research group OPTAVER where the goal is to build up the whole manufacturing process, from the CAD, over the simulation, to the fabrication process and coupling of such printed POWs.

Sensing in harsh environments, such as in high magnetic fields like those found within MRI machines or in high-voltage conditions like those found within power transformers lends itself well for the use of fiber optic sensors. Where conventional electronic sensors fail for obvious reasons, specially designed fiber optic sensors can fill in these gaps. The aim of this research was to investigate the feasibility and technical parameters necessary to design a flexure sensor based on evanescent coupling between the modes of a two- (or more) core fiber. The design parameters are discussed and the sensitivity of the sensor is shown to be tunable by modifying variables which the coupling constant is sensitive to. The physical model used to simulate this system is derived from an effective index change due to a combination of strain and an effective path difference which is induced by bending the fiber. The result of this model is a coupled-mode equation that can be systematically solved using an eigenvector approach to mode coupling. With proper fiber drawing techniques, this model predicts measurement sensitivities of curvature down to km^-1. Furthermore, this technique can be extended based on simulated long-wavelength measurements to make predictions about where along the length of the fiber the flexing took place. This system has the potential to be used as a competing system for Rayleigh backscattering based flexure measurements.

In this paper we theoretically realize the all optical pressure sensor using the Mach-Zehnder interferometer (MZI). In this model, one arm of MZI is plated with silver and surrounded with specially design polymer filled metal cylinder with opening at one side where pressure applied. The MZI structure can be effectively used to sense surface plasmon resonance and used as an efficient pressure sensor. The paper includes the suitable expressions for the optimizing the power entering each branch of the Mach-Zehnder interferometer, the SPR phase and amplitude changes. The results are very effectively supported by the use of COMSOL and MATLAB.

Anisotropic metamaterials are widely used in the field of optics because of their unique electromagnetic properties. These metamaterials can be made from multilayer metallo-dielectric structures. Such stacks can be represented as an anisotropic bulk medium using effective medium theory. Optical properties of anisotropic media are mostly described in terms of effective parameters such as permittivity and permeability, or alternatively, refractive index and characteristic impedance. These properties depend not only on the wavelength and polarization but also the direction of the optical wave-vector. In this work optical wave propagation through such anisotropic media is studied in detail. The Berreman 4 × 4 matrix along with appropriate boundary conditions is used to determine all electric and magnetic fields inside and outside the structure. The overall transmission and reflection are investigated as a function of the thickness of each layer (metal/dielectric), the number of layers, and the wavelength for oblique incidence. The validity of the effective medium theory is also investigated by changing the thickness and number of layers.

Aluminum-doped ZnO (AZO), a wide direct bandgap semiconductor which emits laser light in the ultraviolet range at room temperature, presents a promising optical gain material for creating lasers for applications in photonics, information storage, biology and medical therapeutics. AZO exhibits an excitonic photoluminescence peak in the ultraviolet region and a defect related photoluminescence peak in the visible region. In addition, a recently developed aluminum-doped ZnO nano-layered structure has a unique optical property namely that the dispersion of the dielectric constant exhibits an optical topological transition in the isofrequency surface from an ellipsoid to a hyperboloid. This unusual optical property provides a unique opportunity for creating nanoscale cavities with dimensions significantly smaller than the wavelength of light which could lead to potential applications such as efficient and compact ultraviolet lasers and LEDs. In this work, we investigate the photoluminescence properties of the anisotropic nano-layered aluminum-doped zinc oxide. In order to describe the influence of the aluminum dopants, a complete model for photoluminescence based on the set of rate equations for electron-hole recombination is developed. The set of coupled rate equations is solved numerically using the fourth order Runge Kutta technique for various optical pump intensities. Our calculations predict that the near-band-edge intensity increases with the addition of aluminum (aluminum filling factor up to ~3%) which indicates that the band gap energy increases as the aluminum content is increased.

The reported "stopped rainbow" concept in tapered metamaterial¹ and plasmonic² guiding microstructures has revealed the possibility to obtain local wave enhancement together with spatial chromatic resolution. Recently, this phenomenon has also been demonstrated in graded defect waveguides in photonic crystals³. As the wave is stopped in such single mode defect waveguides, the energy of the stopped wave will be restricted due to the limited volume of the mode, which seriously limits the "brightness" (i.e. its local intensity) of the trapped rainbow. For many applications more desirable would be to stop the light in a bulk of a structure, and to harvest the energy of the stopped wave across all the structure, without any principal restrictions imposed by the mode volume. Such stopping of waves in bulk of a structure has been shown for acoustic waves in sonic crystals recently⁴ and also for electromagnetic waves in multilayer dielectric slabs⁵. However high radiation losses in the latter case are inevitable due to the weak index confinement. Here we present a first experimental demonstration of stopped microwave in a chirped 3D photonic crystals. We show that the complete 3D photonic bandgap may significantly reduce the external losses and we also show that the local intensity can be enhanced up to two order of magnitudes. This allows an important increase of absorption/photodetection of microwave radiation. We further demonstrate that the different microwave components stop and reflect at different depths of the chirped structure, which offers a frequency-resolved microwave detection.

In this work a detailed analysis of the scattering cross-section of silicon Nano-particles with high number of excess carriers in the near and Mid Infrared (MIR) is provided. The effect of different radii of the nanoparticles on the resonance peaks is studied using Mie theory and verified using FDTD. The effect of the level of excess carrier generated on the scattering cross section also analyzed. The study reveals many useful characteristics for such particles which behaves as plasmonic particles in the MIR. Using this study, different particles are designed as scatters in the MIR based on specific dimensions and excess carriers level. These particles can be utilized for infrared spectroscopy of different application such as gas and biomedical sensing in the MIR.

Global shutter is a feature of some CMOS image sensors that allows capture of an entire image at a single point in time. We discuss how the device architecture of InVisage’s QuantumFilm enables global shutter operation by controlling the bias on the device stack without an additional transistor, giving high shutter efficiency in a 1.1 μm pixel CMOS image sensor. We use drift-diffusion device simulations to inform our design and reveal device and material properties that are key for carrier selectivity. Based on our device model, we fabricated global-shutter-enabled QuantumFilm devices for near infrared sensing applications and present a characterization of our devices.

In this paper, total internal reflection (TIR) mirror is carefully simulated for silicon nitride polygonal ring resonator sensor structure. Polygonal resonator has recently attracted much attention for applications in bio and chemical sensors because it does not have a bending loss, and it has an advantage of using MMI coupler. In polygonal resonator sensor design, high Q-factor and low TIR mirror loss are extremely significant factors. Therefore, critical angle and Goos-Hanchen shift should be considered in the design of TIR mirror. When cladding material is SiO₂, the critical angle of SiN_x waveguide is about 44.99 degrees and the Goos-Hanchen shift is about 400 nm at 1.55 μm wavelength. For the rib type waveguide, we designed it to have 3 μm width, 1 μm height, and 0.5 μm etching depth for decreasing TIR mirror loss. As simulation results of FDTD, reflectivitities of polygonal TIR mirrors are 79% for pentagon, 95% for hexagon and 98% for octagon, respectively. According to the simulations, Q-factors for hexagonal and octagonal resonators can be obtained as high as 1.55 x 10⁴ and 1.72 x 10⁴, respectively.

Multi-core fibers are recognized as the medium designed to be used in telecommunication for space division multiplexing. At the same time, they can be advantageously used in sensor technology. The most crucial parameter for multi-core fibers is crosstalk, as its presence at a high level is found to be highly undesirable in telecommunication applications. However, this phenomenon can be used advantageously in the construction of new types of fiber optic sensor.

For the strain sensor, we used a dual-core microstructured fiber. In the research presented, we take advantage of the technology of fiber post-processing, namely fiber tapering. This treatment, which enables changes in the conditions for interference between supermodes, makes the fiber sensitive to elongation. In the un-tapered section, supermodes do not interfere efficiently (crosstalk <-50 dB), whereas in the tapered section the crosstalk increases significantly (crosstalk = 0 dB meaning all the power from one core can be transferred to the neighboring core), creating a strain sensitive area. The distribution of power between the cores of a multi-core fiber at the output of the sample depends on the elongation of the sample. The strain value can be read off both in the domain of power and wavelength. Research results show that sensor performance can be adjusted by changing the taper length and ratio. The results presented are promising for the construction of a temperature independent strain sensor, whose strain sensitivity (17nm/mε) is far better than optical fiber sensors based on Fiber Bragg Gratings. Meanwhile, the temperature sensitivity is negligible assuring no cross-sensitivity.

Fixed focus systems have long been the mainstay in the field of industrial camera technology. This has limited the applications where vision systems could be used. Increasingly, we are seeing vision applications that involve movement or target variability where autofocus is becoming a requirement. The traditional methods of implementing autofocus can be cumbersome and limited. As new technologies emerge in the field of autofocus, being able to adapt them to the industrial camera technology is key. By incorporating these new technologies, such as liquid lenses, with existing camera technology, we can now provide small, very fast, reliable autofocus solutions to the industrial marketplace. This changes the paradigm for industrial camera technology and opens a wide range of new imaging applications and markets.

In this work carrier transport mechanism in strain balanced SiGeSn/GeSn QWIP is studied to obtain the frequency response. Initially, a QWIP model is proposed in which a 76Å thick Ge_0.83Sn_0.17 layer is sandwiched between two tensile strained Si_0.09Ge_0.8 Sn_0.11 layers to form a type-I single strain balanced quantum-well infrared photodetector (SQWIP). The rate equation in quantum well and continuity equation over the well are solved simultaneously to obtain frequency response. The 3dB bandwidth obtained from frequency response is evaluated as 47 GHz at zero bias which increased with the applied bias. Also, the effect of bias dependent escape rates of carrier from the quantum well on the 3dB bandwidth is studied.

In this work, multi-parameter fiber optic sensing setup is demonstrated by the simultaneous analyses of curvature and transversal load. The experimental arrangement operates by using two compact all fiber Fabry-Perot interferometers. Using a 2x1 optical fiber coupler the reflected interference patterns provided by each interferometer are combined, consequently new interference spectrum is obtained. Overlapping interference spectra is generated, and when curvature and load are simultaneously applied, intensity and phase variations are independently observed. The load information is obtained through a wavelength shifting generated by one interferometer, meanwhile the curvature data were analyzed using the intensity modulation provided by the other interferometer. The load analysis presents sensitivity around 0.1nm/N and moreover the experimented curvature shows a resolution of 0.4*10^-3cm^-1.

We present a method based on total internal reflection (TIR) phenomenon for measuring the refractive index (RI) distribution with high-precision. In the field of RI measurement, the method based on TIR phenomenon is usually used to detect the average RI of the sample under tested, but unable to get the detail of RI distribution. We present a new method, using the micro-lens array to split the beam of light and divide the testing surface into a certain number of tiny detection areas. With the detector of area CCD camera, each pixel collects the reflected light from each tiny detection area respectively. By analyzing the reflectivity to each tiny detection area, we can get RI information of each tiny area. Through theoretical calculation and the actual scaling, the RI value of each spot is obtained. After collecting the RI of each tiny area, we can obtain the RI distribution.

In this study, J-K flip-flop is proposed utilizing electro-optic effect of lithium niobate based Mach-Zehnder interferometers (MZIs). J-K Flip flop is most versatile flip-flop amid basic flip-flops. It has vast applications in data storage, data transfer, frequency division, binary counters etc. Lithium niobate (LiNbO₃) based MZIs provide both the required bandwidth and the equally important means for minimizing the effects of dispersion. The work is carried out by simulating proposed device with Beam propagation method. The paper also constitutes the mathematical description of device and thereafter simulation using MATLAB.

Graphene has attracted much attention due to its unique optical properties as a new kind of plasmonic metamaterial in the terahertz regime. Here, we theoretically investigated a wavelength tunable plasmon induced transparency (PIT) device based on graphene metamaterials which is composed of periodically patterned graphene nanostructures. The interactions and coupling between plasmonic modes are investigated in detail by analyzing the field distributions and spectral responses. The coupled Lorentz oscillator models are used to explain the physical mechanism of the PIT. The finite-difference-time-domain (FDTD) method is used to investigate the tunable properties of the structure. It is shown that the coupling strength between the bright mode and dark mode is tuned by the coupling distance between the elements of the proposed structure. By varying the Fermi level of graphene, the PIT resonant frequency can be dynamically tuned. Furthermore, we demonstrate numerically that tunable slow light can be realized in our patterned graphene metamaterials.

Due to its low cost and simplicity, ion exchange is considered one of the most commonly used processes to produce glass waveguides nowadays. This fabrication technology is based on the substitution of some ions already present in the glass with other ions having different sizes and polarizabilities. A careful study of the resultant refractive index profile is crucial in the impact on the waveguide characteristics. In this paper, we introduce, for the first time, a novel solution of the nonlinear diffusion equation that model this process using finite element method (FEM) approach. The ion exchange can be modelled as a nonlinear diffusion equation, as the exchanged ions Ka+ diffuse into their new sites where the original ions were existing. Numerical instabilities are encountered when solving for the exchanged ions with similar diffusion coefficients as in the case of Ka+/Na+, which is used in fabricating integrated optical devices with refractive index differences compatible with those of the optical fibers. Different novel FEM techniques are proposed in solving the problem in 1D space. The stability and accuracy of the different methods outperforms the current numerical methods and provide a good tool for highly nonlinear diffusion problem.

Optoelectronic feedback (OEF) system plays an important role in nonlinear dynamics because of low-cost and easy to generate dynamical states, including regular pulsing (RP), quasi-pulsing (QP), and chaotic pulsing (CP). However, the non-ignored noise naturally generated by delay-loop frequency in the dynamical states is the most important problem to be solved. In this paper, we focused on the generation of RP states and also on the improvement of the noise reduction in the RP states by utilizing the double-delay system. The double-delay system is built up by optical feedback (OF) and OEF systems. When adjusting four controllable parameters of OEF delay time, OEF feedback strength, OF delay time, and OF feedback strength, more complex dynamics are obtained compared to those observed in individual OF and OEF system. Moreover, noise reduction of the RP states caused by the mixing of delay loop frequencies in double-delay scheme is realized by applying an additional OF delay loop to the already-generated RP states by OEF scheme. To explore the quality of the generated RP states, the measurements of amplitude variation in time series and the single-side band phase noise in frequency domain are examined. As a result, effective noise reduction in RP states is achieved while applying a weak OF feedback strength and a short OF delay time. Furthermore, no common factor in these two delays is necessary to observe stabilized RPs and the amplitude variation down to 0 which is equal to 100 percentage noise reduction is achieved while fine-tuning the controllable parameters carefully.

Nonlinear dynamics of semiconductor lasers under individually optoelectronic feedback (OEF) and optical feedback (OF) is attracted much attention in these two decades. However, according to my knowledge, there is no related research results in dual-feedback system composed of optical and optoelectronic feedbacks. In this paper, the nonlinear dynamics of the dual-feedback system is studied and applications in generation of broadband chaos and stabilized pulses based on quasi-periodic (QP) states are achieved. Generally, QP states do not have contributed application which limited the research attention in recent years. Here we focused on the QP state and turned it to be the useful chaos and pulses. The QP is firstly generated by pure OEF system and then applying an additional OF system to obtain the chaos and pulses by tuning the controllable conditions of feedback strength and delay time. To explore the rich dynamics of the dual feedback system, mappings of each dynamical states are calculated, including regular pulsing, periodic oscillation, and chaotic oscillation and pulsing states. Furthermore, chaos bandwidth and amplitude variation of regular pulses are examined to quantify the signals generated. A 2-fold improvement of chaotic oscillation frequency is observed in dual feedback system compared to the chaos generated by pure OEF system. Broadband bandwidth of chaotic oscillation is obtained in dual-feedback system when using a relaxation oscillation frequency of 2.5 GHz laser in the free-running condition. Moreover, the improved percentage of averaged amplitude variation in regular pulses is around 81.6% compared to those generated by pure OEF scheme.

Many technical applications need laser beam reshaping, which represents redistribution of optical power in the beam cross-section; particularly to form a flat-top beam. Such systems synthesis requires to develop a specific mathematical model that could be installed then into special commercial software. This work describes laser beam reshaper modeling using two aspherical lens telescopic system. Also are shown approximation equations of refractive aspherical surfaces and the reshaping optical system model applying Zemax software.

In this work, two-dimensional modeling of planar junction AlInAs avalanche photodiodes is reported. Modeling results of dark/photo current, multiplication gain, breakdown voltage, -3dB bandwidth and gain-bandwidth product, and excess noise etc., are presented. The modeling results of multiplication gain and -3dB bandwidth are consistent with the reported experimental demonstration. Design optimization is also explored for high gain-bandwidth product for such AlInAs avalanche photodiodes.

Implementation of hybrid scanning system in wide and narrow angle fields provide high precision positioning of the laser beam in space, fraught with difficulties. Scanning attachment for SRS - lidar system has been developed to perform automated scanning of the test area in the angular field of ± 50. The module performs automated scan of the test area in the angular field of ± 50 on 50-100 m distance. Movement of the laser beam in a spiral occurs due to rotation in one direction wedges with different speeds, which speed is in the range of 50-200 Hz. The laser beam had a divergence of 1.5 mrad. Because the spatial resolution at the outer coils falls compared with the center spiral wedges speeds ratio increases from 0.8 to 0.97, respectively.

High power laser diodes have found a wide range of industrial, space, medical applications, characterized by high conversion efficiency, small size, light weight and a long lifetime. In this investigation, high power 940 nm laser bars were mounted on optimized micro-channel heat sinks (MCC) using AuSn/CuW and In Soldering schemes. The optimized MCC cooler has decreased pressure drop and increased heat-sinking capability. The improvements in thermal and strain characteristics will be reported through wavelength, thermal rollover, spatial spectrum, SMILE, and polarization.