This PDF file contains the front matter associated with SPIE Proceedings Volume 12218, including the Title Page, Copyright information, Table of Contents, and Conference Committee Page.

In this work we demonstrate a proof-of-concept depolarization emulator that generates customized spatial patterns of the polarization state (SoP) and degree of polarization (DoP). It is based on a pixelated LCOS-SLM addressed with a spatially time-varying retardance function. Three different cases featuring spatial control of the DoP are realized to show the potential of the method, including a spirally-shaped depolarization pattern. The polarization properties of the output light beam are verified by imaging the SLM screen onto a polarizing camera and performing Mueller matrix imaging polarimetry. We obtain the time-averaged Mueller matrix of the SLM and show that the output effective polarization state is governed by the averaged retardance, while the degree of polarization is governed by the retardance semidifference. An intuitive explanation of this performance is provided in the Poincaré sphere. The proposed technique could be useful in testing imaging polarimeters, in laser beam manipulation and in biomedical imaging, where emulating depolarization effects with controlled precision can help understand the physical mechanisms that cause depolarization.

Pairs of entangled photos are used to reconstruct an image in the application area known as quantum ghost imaging. It is the correlation between the photon pair that allows for the reconstruction of the image, as opposed to single photon detection. The entangled photons are spatially separated into two independent paths, one to illuminate the object and the other which is collected by a spatially resolving detector. Initially, ghost imaging experiments accomplished spatially resolving detectors by moving a single-pixel detector throughout a transverse scanning area. Advancements consisted of using ultra-sensitive cameras to avoid a system consisting of physically moving detectors. Ultra-sensitive cameras are, however, expensive and have limited spectral sensitivity. Here we demonstrate an alternative by utilising a spatial light modulator and a bucket detector to spatially resolve what is detected. Importantly, the masks displayed on the spatial light modulator must constitute a complete basis to acquire a completely reconstructed image. Historically, imaging speeds have been slow and inefficient due to the quadratic increase in the scanning capability for spatially resolved detectors and the low light levels associated with quantum experiments. Here we additionally utilise machine and deep learning algorithms to improve both image reconstruction time and resolution. We demonstrate this with a non-degenerate ghost imaging setup where the physical parameters such as the mask type and resolution are varied and controlled on a spatial light modulator. Thereby answering the question: can we image an object without using a camera?

We propose a continuous refractive beamforming surface for far-field with a freeform surface and non-one-to-one ray mapping, realizing the high efficiency and robustness of the XY position. We developed a new iterative optimization algorithm. The major tasks in each optimization step are updating the ray emission angles and surface reconstruction. The update of the ray emission angles is performed by the Monge-Ampère equation considering target and tentative far-field intensity distributions. The surface reconstruction is realized by minimizing the loss function consisting of the reconstruction error and regularization terms concerning the surface’s height and curvature. We also developed a manufacturing process for the freeform surface, which was very close to the design, by providing manufacturing feedback. This manufacturing process consists of the mastering process by a laser grayscale lithography, mold manufacturing process by a Ni electroforming, and producing element process by an imprinting process.

Aberrations produced by transparent optical elements and random scatterers in a focused laser beam are corrected by measuring the phase and then imprinting the phase conjugate onto the beam. The field is represented with a Hadamard basis and the phase contributions of each element are measured with interferometry. We investigate implementing the basis on a Bessel beam, which is projected into a ring and can result in a reduction of the number of elements needed in the basis to get a reasonable correction.

Laser beam propagated through surface layers of the atmosphere changes its properties under influence of the turbulence effect. To mitigate the consequences of its adaptive optics tools are widely used. In this paper the optimization of main parameters (stroke, first resonance frequency, substrate and piezoplate layers thicknesses) of the bimorph wavefront corrector was performed considering severe atmospheric conditions (refractive index structure constant C_n²=10^-13 m^-2/3, length of the trace L = 500 mm, beam diameter D = 300 mm, wavelength λ = 1064 nm, Fried parameter r_o = 34 mm, wind velocity v = 10 m/s).

Wavefront correction efficiency by bimorph deformable mirror could be estimated through the modal functions’ reconstruction. Zernike polynomials at this point could be considered as an effective and easy-to-use tool for this purpose. The 37-channel bimorph deformable mirror was able to reproduce wavefront aberrations up to 7th order with reasonable amplitude and residual RMS of less than 0.05 μ.

Phase-only spatial light modulator with Full HD resolution was applied to focus laser radiation that passed through the thick layer of the scattering suspension. Polystyrene microbeads of 1 μm diameter diluted in distilled water was used as a scattering medium. The concentration values of the suspension were varied from 105 to 106 mm-3. In order to analyze the intensity distribution of the focal spot in the far-field a CCD camera with micro-objective was used. Shack-Hartmann sensor was used to analyze the wavefront distortions caused by the scattering medium. We demonstrated that the assembled experimental setup can increase the integral intensity of the focused light by approximately 10% while simultaneously decrease the focal spot size by approximately 20%.

Laser beams can be shaped by controlling either the intensity or phase or coherence distribution separately. With typical laser configurations, the intensity and phase controls are relatively slow and cannot yield high-resolution arbitrarily shaped beams and the coherence control suffers from high power loss. By resorting to a degenerate cavity laser that incorporates an intra-cavity digital spatial light modulator and an intra-cavity spatial Fourier filter, it is possible to exploit a very large number (about 100,000) of independent lasing spatial modes in order to control the properties of the laser output. We have adapted this configuration to develop a novel, rapid and efficient method to generate high resolution laser beams with arbitrary intensity, phase and coherence distributions.

In this paper, the simulation of a 2-kW laser demonstrator using a free-space incoherent beam combining based on two laser diodes stacks at 980 nm is presented. The implementation of the simulations is done in Optic Studio Zemax software. The goal of this work is to design and validate the feasibility of the construction of an experimental laser demonstrator in a laboratory for rapid prototyping of high-power laser sources. The simulation results are characterized using power density at a detector, beam parameter product, and spot size as descriptors.

Micro-Opto-Electro-Mechanical resonant micromirror featuring a 4 mm aperture for laser-based measurement is presented. The MOEMS-mirror is fabricated on an SOI-wafer with piezoelectric actuators based on aluminium nitride thin films and packaged in a vacuum for a high-efficiency operation. The design of the device features four symmetrical co-radial beam structures, where each beam structure incorporates discrete piezoelectric elements for actuation and sensing. The integrated sensing element provides an accurate and real-time feedback signal for the control system, as it is directly mechanically coupled to the source of movement. Symmetrical design allows the mirror to be excited in the desired mode by modifying the frequency and phase on each of the driving actuators. For the laser measurement applications driving the mirror opposite actuators in opposite polarity and perpendicular axis with different frequencies, creates up to a 40-degree field of view Lissajous scanning pattern. The amplitude of the resonance is strongly affected by the Duffing-type nonlinearity and the derivative of the amplitude vs. frequency curve is small, allowing relatively large changes of frequencies without affecting the amplitude. Phe presented digital control method allows adjustment of frequencies via a phase accumulator to control Lissajous pattern parameters: ratio, phase and amplitude. Due to the high efficiency of aluminium nitride actuators and high Q value, a direct low-voltage CMOS interface can be implemented between the digital control system and piezoelectric actuators. The high amplitude feedback signals allow straightforward conversion to the digital domain and enable monitoring of operation mode and phase.

The paper presents an analysis of the efficiency of using bimorph and piezostack deformable mirrors for scattered laser radiation focusing. In this paper, we study the beam focusing efficiency with the use of a piezostack deformable mirror with 61 piezoactuators and an aperture of 60 mm, as well as a bimorph deformable mirror with 48 electrodes and an aperture of 50 mm. It is shown that such mirrors can be successfully used to optimize the focal spot formed by scattered radiation in the far-field.