Freescale's production 0.13μm SOI process is used to fabricate all required electrical and optical components for 10Gb interconnect up to 2000m using only 1.7W. The optical transceiver cores are monolithically fabricated with CMOS circuitry required for bias and control as well as the electrical PHY interface. Optical multiplexing of 4 to 10 channels allows scaling to 40/100Gb.

The optical components industry stands at the threshold of a major expansion that will restructure its business processes and sustain its profitability for the next three decades. This growth will establish a cost effective platform for the partitioning of electronic and photonic functionality to extend the processing power of integrated circuits. BAE Systems, Lucent Technologies, Massachusetts Institute of Technology, and Applied Wave Research are participating in a high payoff research and development program for the Microsystems Technology Office (MTO) of DARPA. The goal of the program is the development of technologies and design tools necessary to fabricate an application-specific, electronicphotonic integrated circuit (AS-EPIC). As part of the development of this demonstration platform we are exploring selected functions normally associated with the front end of mixed signal receivers such as modulation, detection, and filtering. The chip will be fabricated in the BAE Systems CMOS foundry and at MIT's Microphotonics Center. We will present the latest results on the performance of multi-layer deposited High Index Contrast Waveguides, CMOS compatible modulators and detectors, and optical filter slices. These advances will be discussed in the context of the Communications Technology Roadmap that was recently released by the MIT Microphotonics Center Industry Consortium.

Progress in developing high speed ADC's occurs rather slowly - at a resolution increase of 1.8 bits per decade. This slow progress is mostly caused by the inherent jitter in electronic sampling - currently on the order of 250 femtoseconds in the most advanced CMOS circuitry. Advances in femtosecond lasers and laser stabilization have led to the development of sources of ultrafast optical pulse trains that show jitter on the level of a few femtoseconds over the time spans of typical sampling windows and can be made even smaller. The MIT-GHOST (GigaHertz High Resolution Optical Sampling Technology) Project funded under DARPA's Electronic Photonic Integrated Circuit (EPIC) Program is trying to harness the low noise properties of femtosecond laser sources to overcome the electronic bottleneck inherently present in pure electronic sampling systems. Within this program researchers from MIT Lincoln Laboratory and MIT Campus develop integrated optical components and optically enhanced electronic sampling circuits that enable the fabrication of an electronic-photonic A/D converter chip that surpasses currently available technology in speed and resolution and opens up a technology development roadmap for ADC's. This talk will give an overview on the planned activities within this program and the current status on some key devices such as wavelength-tunable filter banks, high-speed modulators, Ge photodetectors, miniature femtosecond-pulse lasers and advanced sampling techniques that are compatible with standard CMOS processing.

The most recent impetus for the convergence of photonics and silicon integrated circuit technology has been the looming communications bottleneck associated with chip-to-chip and on-chip high-speed data transfer. Whilst there have been significant separate improvements in the materials and technologies for both integrated optics and integrated electronics, there is now a real commercial interest in putting these pieces together to achieve functional circuits that take advantage of both technologies. It is the purpose of this paper to review the recent developments in both microelectronics and photonics that are causing these fields to merge in the area of on-chip and off-chip data links.

With a reverse biased p-i-n structure embedded in a silicon waveguide, we efficiently reduced the nonlinear loss due to two photon absorption induced free carrier absorption and achieved continuous-wave net Raman amplification and lasing in a silicon waveguide on a single chip. The low-loss p-i-n waveguides also enabled efficient wavelength conversion in the 1550 nm band via four-wave mixing in silicon. Here we report the performance characteristics of the silicon based laser, amplifier as well as wavelength converter for different device configurations. With a pump wavelength at 1550 nm, the laser output at 1686 nm is single mode with over 55 dB side mode suppression and has less than 80 MHz linewidth. At 25V reverse bias, the threshold pump power is ~180 mW. The slope efficiency is ~4.3% for a single side output and a total output power of >10 mW can be reached at a pump power of 500 mW. The laser wavelength can be tuned by adjusting the wavelength of the pump laser. A 3 dB on-chip amplification and -8.5 dB wavelength conversion efficiency is achieved in an 8-cm long waveguide at a pump powers of < 640 mW. We demonstrate that a high-speed pseudo-random bit sequence optical data at 10 Gb/s rate can be amplified or converted to a new wavelength channel with clear open eye diagram and no waveform distortion.

We have investigated the molecular beam epitaxial growth and characteristics of self-organized InGaAs quantum dot lasers grown directly on silicon utilizing thin (≤2 μm) GaAs buffer layers and quantum dot layers as dislocation filters. Both the photoluminescence intensity and linewidth from quantum dots grown on silicon are comparable to those from similar dots grown on GaAs substrates. Cross-sectional transmission electron microscopy studies indicate that defect-free quantum dots and low defect density quantum dot active regions can be achieved. The best devices are characterized by relatively low threshold current (J_th ~ 900 A/cm²), high output power (> 150 mW), large characteristic temperature (T₀ = 244 K) and constant output slope efficiency (≥ 0.3 W/A) in the temperature range of 5 to 95 °C.

Emitting 1530 nm light on Silicon wafer is very useful because 1530nm is an important band in optical fiber communication. We explore a new way of light emission at 1530 nm. We demonstrate a simple and non-expensive process to form light-emitting layer. It can be deposited on silicon wafers. The properties of samples can be varied through controlling the composition. The emission efficiency can be further improved by introducing P₂O₅ and Yb₂O₃ nanoparticles into the solution. This emitting layer is able to show the signals only within several millimeters due to surface effect of nanoparticles, enabling the higher concentration of Er³⁺. The optical gain at 1530nm is measured using variable stripe length method. The gain coefficient can be as large as 18 cm^-1.

In this paper a review of the reported approaches to achieve an injection Silicon laser is presented. After an initial discussion of the basic on light amplification and gain in semiconductor, we consider the limitations of silicon, in particular its band structure. Then the various approaches to get an injection silicon laser are presented and evaluated: bulk silicon, silicon nanocrystals, Er coupled silicon nanocrystals.

Monolithic integration of both electronic and optic components into a silicon-based platform will provide high-speed optical interconnects and solve the power-bandwidth limitations. However, the lack of strong optical effects in silicon has limited the progress in the transmitter-end applications. Recently our research had demonstrated strong quantum-confined Stark effect (QCSE) in germanium quantum-well modulators on silicon. This first strong physical mechanism for group-IV photonics has a comparable behavior to III-V material systems. With proper quantum well structure design, we also demonstrated QCSE in C-band for long distance communications with CMOS-operational temperatures. The device fabrication is also compatible with standard silicon chip processes. Since the QCSE, a type of electroabsorption effect, requires much shorter optical length, it is suitable for device miniaturizations and possible for use in both lateral and vertical modulator configurations. Moreover, silicon-germanium electroabsorption modulators are inherently photodetectors, this advantage will enable efficient transmitter/receiver applications for optical interconnects.

We report the design of a 10 GHz non-return-to-zero (NRZ) silicon modulator based upon 0.25-μm CMOS/BiCMOS processes. The basic optical component is a ridge waveguide slightly-doped with P and N impurities, which forms a reverse-biased P/N junction. The diode typically operates between reverse and zero biases, so as to change the number of free carriers overlapping with the optical mode and consequently modulate the phase of the light. This type of phase shifters form the arms of a push-pull Mach-Zehnder interferometer to realize amplitude modulation.

Photonics on CMOS is the integration of CMOS technology and optics components to enable either improved functionality of the electronic circuit (e.g. optical clock distribution) or as a means to miniaturize optical functions (e.g. miniaturised transceiver). The Near Infra Red (NIR) wavelength range (1.3 or 1.55μm) was chosen for this to minimise the impact the light on the behaviour of the microelectronic components. The integration of a photonic layer on a CMOS circuit can be seen in different ways: A combined fabrication at the front end level, the wafer bonding of an SOI photonic circuit at the back-end level, or the insertion of an embedded photonic layer between metallization schemes. For combined fabrication, a silicon on insulator rib technology has been developed with low (0.4dB/cm) propagation loss, ultra-high speed Ge-on-Si photodetector and SiGe/Si modulators.. In the metal-semiconductor-metal (MSM) configuration, bandwith of 35 GHz at 1.3 μm and 1.55μm has been measured. In the second approach, a wafer bonding of silicon rib and stripe technologies was achieved above the metallization layers of a CMOS wafer. For the third method, direct fabrication of a photonic layer at the back-end level was achieved using low temperature processes. Waveguide technologies such as SiNx (loss 2dB/cm) or amorphous silicon (loss 5dB/cm) were developed and were followed by the molecular bonding of InP die, these were needed to create the optoelectronic components (sources and detectors). Using an InP microdisk, 50% coupling was achieved to a stripe silicon waveguide.

This paper describes a silicon photonic circuit of eight fiber-optic input ports, each port leads through an electro-photonic modulator to a 0.95/0.05 coupler, where the 95% signal is guided to a fiber-optic output port and the 5% signal is terminated by a vertical coupler and a down-looking photodetector. Applications include telecommunication equipment requiring microsecond speed for rapid power balancing, transient suppression, and subcarrier modulation for channel tracking and system health monitoring. Circuit elements and initial measurements are described.

The development of monolithic silicon photonic systems has been the subject of intense research over the last decade. In addition to passive waveguiding structures suitable for DWDM applications, integration of electrical and optical functionality has yielded devices with the ability to dynamically attenuate, switch and modulate optical signals. However, for silicon to dominate as the substrate of choice for the fabrication of photonic circuits, the development of a full range of monolithically integrated functionality is required including detectors capable of signal monitoring at a wavelength around 1550nm. Photodetectors integrated with silicon-on-insulator rib waveguides are here demonstrated. Significant response at infrared wavelengths is shown to be mediated via deliberately introduced deep band-gap levels. This paper describes in detail the device fabrication and the performance of the waveguide photodetectors with regard to photoresponse, bandwidth, polarization sensitivity and thermal stability. Currently typical devices tap between 10-20% of an optical signal from an SOI waveguide and generate a photocurrent of several micro-amps. The most efficient device extracted 19% of the optical signal while exhibiting a responsivity of 3mA/W. We also describe results from the operation of an integrated photonic circuit consisting of a variable optical attenuator (VOA) and a photodetector. The detector monitors the optical signal as it is modulated using the VOA, however there exists a small, systematic offset in response as compared to measurements made with an external detector.

We present the heterogeneous integration of InP/InGaAsP photodetectors onto ultracompact Silicon-on-Insulator (SOI) waveguide circuits using benzocyclobutene (BCB) die to wafer bonding. This technology development enables the integration of a photonic interconnection layer on top of CMOS. Fabrication processes were optimized and the transfer of a passive Silicon-on-Insulator waveguide layer using BCB was assessed.

A monolithically integrated asymmetric graded index (GRIN) waveguide structure for coupling light into high index contrast waveguides is described. When analyzed in terms of its waveguide modes, the GRIN coupler is shown to be a multimode interference (MMI) device. The design parameters and tolerances are calculated for quadratic index profile and uniform index amorphous silicon (a-Si) GRIN couplers optimized for coupling light into silicon-on-insulator waveguides. Calculations of coupling efficiencies into 0.5 μm SOI waveguides show that asymmetric GRIN couplers operate over a very wide wavelength range with low polarization dependence, and fabrication requires lithographic resolution of only ±1 μm. Experimental results are presented for a 3 μm thick single layer a-Si coupler integrated with a 0.8 μm SOI waveguide. The measured variation of coupling efficiency with coupler length is in agreement with theory, with an optimal coupling length of 15 μm.

The single-mode optical rib waveguide is a fundamental building block for many, more complex optical circuits. Recent modelling has been provided in the literature that has investigated polarisation and modal properties of small, deeplyetched rib waveguides in SOI. In this paper we present work that has utilised a total of 160 directional couplers fabricated from rib waveguides of various waveguides dimensions, to investigate the validity of the published modelling. In particular 5 waveguide designs have been used to fabricate directional couplers of differing lengths, to map out the variation in coupling of power within the directional couplers. For a singlemode device, a characteristic sinusoidal variation is expected, but the sinusoid will be corrupted in the presence of higher order modes, each of which will have a different coupling length as compared to the fundamental mode. We have observed experimental results that are consistent with the modelling for each of the 5 waveguide designs, and hence we present experimental evidence of higher-order mode behaviour that is consistent with modelling.

Stellar interferometry is an old technique (first successful measurement of Titan diameter by Michelson in 1890), which have recently been dramatically improved by the implementation of integrated optical devices. The technique, consisting in combining coherently several beams coming from distinct telescopes, allows to reconstruct images with a very high angular resolution, typically 10 times better than the diffraction limit of the biggest telescopes on Earth and about 20 times better than the Hubble space telescope. During the last few years, LETI, in collaboration with IMEP (Institut de MicroElectronique et Photonique) and LAOG (Laboratoire d'Astrophysique de l'Observatoire de Grenoble) has developed several components for stellar interferometry, either using its well-established silica on silicon technology, or developing a new silicon technology for mid-infrared metallic hollow waveguides adapted for the ESADARWIN mission. This paper will present the latest developments made by LETI in this field, describing the silicon technologies involved, the realized devices as well as their behaviour on laboratory set-ups or on the sky.

Modal properties of silica waveguides are presented along with their results on single mode operation, spot-size variations, confinement factor and, modal field profiles for different index contrast value between the core and the claddings. Both dominat and non-dominat field profiles and their transverse variations are also shown. Numerically simulated results also suggests that by using the MM-based design a very compact optical power splitter, of the order of 500 μm in length, can be designed, which is much shorter than conventional directional coupler or Y-junction-based designs.

We discuss the development of novel integrated optical sensors with single molecule detection sensitivity. These sensors are based on liquid-core antiresonant reflecting optical waveguides (ARROWs) that allow for simultaneously guiding light and molecules in liquid solution through micron-sized channels on a chip. Using liquid-core ARROWs as the main building block, two-dimensional planar sensor arrays with sensitivity down to the single molecule level can be fabricated. We present the basic design principle for ARROW waveguides and methods to improve waveguide loss. The influence of surface roughness on the waveguide loss is described. We discuss highly efficient fluorescence detection in both one and two dimensional planar waveguide geometries. Avenues towards subsequent integration with microfluidic systems are presented.

Recently, integrated optic applications on SOI substrate like add-and-drop structures or wavelength filters based on microdisk resonators have been investigated by many research groups. Microdisks exhibiting high quality-factor thanks to the high refractive index contrast between silica and silicon materials have been already reported. However efficient components usually show few micrometers diameter which is huge compared to photonic crystals ones. In this paper, realization and characterization of efficient and compact components are reported. The dropped-wavelength function, composed of a 1.5 μm radius disk and 0.3 μm x 0.3 μm square section waveguides is demonstrated. 22 dB extinction ratio is measured from spectral measurement while keeping a quality factor of 1000. In this structure, the distance between the microdisk and the waveguide is discussed from experimental point of view. Indeed, the efficiency of the add-and-drop strongly depends on this parameter. Moreover, a wavelength filter based on a 4 μm radius microdisk is also shown. Quality-factors of 92,900 ± 5500 were measured showing that these filters are more efficient than equivalent microring filters. A 10 dB extinction ratio of the wavelength rejected signal is reported. For some resonance wavelengths, spectral response degeneracy of the filter appears. An explanation of this effect is given in this paper.

Surface waveguides for telecom applications are typically SiO₂-based, low-contrast surface waveguides because these applications are dominated by the need for low optical attenuation and low polarization effects across the 1300-1600 nm band. Conventional waveguides, however, comprise films as thick as 20 micron and have minimum bend radii of tens of millimeters. These factors make conventional waveguide circuits large and expensive, and this has limited their use to relatively few applications. In the integrated optical sensing field, the waveguides typically used are (very) high-contrast waveguides. Here, especially Si₃N₄-core waveguides are well-known to offer much smaller bending radii (tens to hundreds of microns) due to stronger mode confinement to the core. Since they also typically comprise sub-micron core-thickness and cladding-thickness of only a few microns, high-contrast waveguides promise lower cost than low-contrast waveguides. Their use in telecom applications has been limited, however, due to strong polarization effects. Recently, LioniX, BV has developed the TriPleX^TM waveguide, which promises to be a well-suited platform for both telecom and sensing applications and is based on low-cost, CMOS-compatible LPCVD processing. TriPleXt^TM technology provides high-contrast waveguides with very low channel attenuation and modal birefringence that is controlled through waveguide design alone. Early experiments on typical geometries show promising waveguide characteristics (attenuation << 0.5 dB/cm, IL ≤ -2 dB, PDL << 1 dB, bend radius << 1 mm). In this paper, we present the characteristics of this TriPleX^TM technology, and show devices that have demonstrated utility in telecom and/or sensor applications using medium and high-contrast waveguides. Experimental results for an MZI-based sensor platform, suitable for liquid or gaseous sensing, are also provided.

Microspheres possess high quality factor morphology-dependent resonances, i.e., whispering gallery modes. Additionally, silicon is proving itself to be an excellent optical material. We have studied the feasibility of silicon microspheres as a optical filters at THz communication frequencies. The silicon microsphere has a radius of 500 μm and a refractive index of 3.4. Elastic scattering spectra are calculated for TE and TM polarizations for wavelengths between 90 μm and 100 μm in the THz communication band. The high quality factor morphology dependent resonances are found to have a repetitive mode spacing of 1.2 μm.

We report the development of a novel low energy optical switch that consists of a silica microsphere optical resonator coated with a layer of silicon nanocrystals. A 150 μm-diameter silica microsphere was coated with a 140 nm thick layer of silicon rich silicon oxide (SRSO) by PECVD. The microsphere/SRSO was annealed in argon at 1100C to facilitate nanocrystal growth. The optical properties of the microsphere were characterized by evanescently coupling 1450 μm tunable laser light through a tapered optical fiber into the whispering gallery mode resonances of the microsphere. A quality factor of 3×10⁵ was measured at this wavelength. Light from an Ar⁺ laser at 488 nm was introduced into the tapered fiber and was used to excite the nanocrystals near the whispering gallery modes (WGM) of the sphere. WGM resonance wavelengths shifts of 5 pm at an operating wavelength of 1450 nm were observed when the Ar⁺ light was coupled into the tapered fiber. Powers as low as 3 μW were sufficient to shift the resonance by a half a linewidth and cause full switching of the 1450 nm signal with a fast rise time (which was limited by the time width of the laser pulse). The speed of the switch is limited by the fall time, which has a time constant of 30 ms.

A new class of miniaturized monolithic silicon optoelectronic transducers properly functionalized to biosensors is outlined. The devices are based on biofunctionalized optocoupler arrays made on silicon by employing mainstream silicon integrated circuit technology. The optocouplers consist of silicon avalanche diodes operating as light emitting devices self aligned to thin silicon nitride waveguides and silicon detectors. Bioanalytical results that demonstrate the efficiency of the device are provided and include protein and DNA detection. Label free determinations are also demonstrated. The optical microdevices are suitable for multianalyte portable bioanalytical microsystems and present unique advantages due to their monolithic optical detection and small size.

Visible light emission from the porous silicon (PSi) formed by anodic etching of Si in HF solution has raised great interest in view of possible applications of Si based devices in optoelectronics. In particular, multilayers consisting of periodic repetition of two PSi layers whose refractive indices are different can be exploited to design interference filters for controlling the emission wavelength as well as for the spectral narrowing of the wide emission band of Psi. Fabry-Perot optical microcavities with an active layer of λ\2 or λ sandwiched between two Bragg reflectors, consisting of alternating layers of high and low refractive indices are fabricated on heavily doped p-type silicon. We have investigated the optical properties of these microstructures using reflectivity and photoluminescence measurements at various temperature.

We fabricated infrared Fabry-Perot filters by stacking two wet-etched Si plates. When an electric voltage was applied between the plates, the spacing between the plates changed due to an electrostatic force, which caused a shift of interference peaks. The Si plates were etched in a KOH solution to 34-μm thickness in order to reduce the driving voltage. When the voltage was raised from 0 to 20 V, an interference peak shifted from 7.9- to 5.5-μm wavelength, corresponding to the decrease in the spacing from 7.9 to 5.5 μm. The peak transmittance increased to 91% by an antireflection coating on the outer surface of the filter. This coating was effective to suppress the interference inside the Si plates that created a complicated spectrum.