This PDF file contains the front matter associated with SPIE Proceedings Volume 11486, including the Title Page, Copyright information and Table of Contents.

A variety of methods have been developed in the last years to generate vector beams. In this work we will present some techniques that we have developed for the efficient and compact generation of arbitrary polarized vector beams. They are based on the use of geometric-phase elements combined with liquid-crystal on silicon (LCOS) spatial-light modulators (SLM) in a common-path architecture. LCOS-SLMs were used to encode a phase-only diffractive mask that encodes complex functions with high diffraction efficiency. We demonstrate the generation of arbitrary scalar modes and vector beam modes.

We introduce and generate the partially coherent non{canonical vortex beams and study their characteristics. The characterization of these fields by means of its intensity is difficult due to the random fluctuations in space and time of partially coherent fields, but it is demonstrated that the cross{correlation function provides information of the composition, spatial coherence structure and singularities of the non{canonical vortex beams. Our approach is based on experimental measurements and numerical simulations of these beams, which show excellent agreement.

We present a simple mechanism for varying the core diameter of zero-order Bessel beams (BBs) through the use of a commercially available diffraction grating. A standard set-up to generate BBs is employed, based on an annular slit and a lens. Output BBs are made to pass through transmission gratings with different groove densities. Core diameters and propagation behavior are modified for BBs diffracted by gratings at diffraction orders m = 0 and m = 1.

Ultrashort pulses (picoseconds or less), are characterized by a high peak intensity that usually leads to nonlinear interactions. Recently ultrashort pulses with orbital angular momentum have attracted great attention due to their wide field of applications, from super-resolution microcopy, optical tweezers and ultra-fast optical communications to quantum computing and astrophysics. A principal challenge here is the development of robust and effective methods for OAM generation. At the moment few techniques are known to obtain OAM beams in the free space arrangement cylindrical lenses, spiral phase plates or computer-generated holograms have been used. All those techniques imply that pulse is passing through an optical component and thus obtain dispersive broadening. We propose here a method and a device allowing formation of ultrashort optical vortices from an incident ultrashort pulse without its broadening or compensating the pulse chirp acquired previously. Potentially method and device will allow obtain ultrashort vortices shorter than incident pulse. Case study is presented based on spatio-temporal numerical simulation and analytical modeling.

We generate optimised phase masks by using an Iterative Fourier Transform Algorithm (IFTA) and use it for beam multiplexing in an experiment to generate an array of uniform spots in 1D and 2D. We quantify the efficacy of the iterative algorithm experimentally by computing the uniformity and the efficiency and show that the optimised phase masks yield multiplexed beamlets having high uniformity ( 90%). We also find that the algorithm converges within few tens of iterations requiring moderate computational budget and can be useful for almost real-time applications. We compare the performance of the iterative algorithm with global linear corrections in the look-up table (LUT) of a phase limited SLM and find that the former perform with about 20% better efficiency. Besides obtaining array of 1D/2D spots having high uniformity using IFTA, our result exemplifies the use of iterative algorithms for improving efficiency of phase limited SLMs, which is a less explored area of research.

In this work, Stokes polarimetery is used to extract the polarization structure of optical fields from only four measurements as opposed to the usual six measurements. Here, instead of using static polarization optics, we develop an all-digital technique by implementing a Polarization Grating (PG) which projects a mode into left- and right-circular states which are subsequently directed to a Digital Micromirror Device (DMD) which imparts a phase retardance for full polarization acquisition. We apply our approach in real-time to reconstruct the State of Polarization (SoP) and intra-modal phase of optical modes.

This work, based on classical light, was in uenced by quantum applications, where comparison of quantum states is an important issue. Laguerre-Gaussian modes were used to encode and compare two independent signals. Polarization controlled SWAP gate exchanges information between two strings of data, therefore preventing them from the leakage. Comparison is done with kHz frequency, achieved by the Digital Micromirror Device. Detected power, being a single value, represents an overlap of both signals. Presented system is capable to perform direct error analysis together with a normalization procedure, which overcomes the necessity of data post-processing and largely reduces time required for such comparison. We present a calibration procedure, which uses the glass sample to determine the performance of the experimental setup.

We designed a new configuration of acousto-optic spatial light modulator based on biaxial crystal KY(WO₄)₂ (KYW). This material has proved to be a good candidate to fill the gap between paratellurite having high acousto- optic efficiency and quartz having low efficiency but high laser-induced damage threshold. The modulator uses isotropic diffraction by a slow quasi-shear bulk acoustic wave propagating in the autocollimation direction. This ensures good compromise between acousto-optic figure of merit, which is only 30% less than in z-cut longitudinal- wave paratellurite, and high laser-induced damage threshold. The prototype modulator has the spatial resolution of 250 with the central frequency of 100 MHz and the aperture of 20 mm. The designed spatial light modulator is aimed at high-power ultrashort laser pulse shaping applications in near and middle infrared.

Electrowetting controlled liquid lenses have emerged as a useful technique for steering light. In this study, we report on a novel hexagonal cell design of an electrowetting device for two-axis solar tracking. This study proposes an array of these hexagonal electrowetting cell structures to facilitate a planar device that can steer sunlight coming from a range of directions. A proof of concept device is fabricated to demonstrate this design. The hexagonal cell is dosed with two immiscible liquids. The liquid-liquid interface is modulated by varying the voltage to different electrode faces in the cell. By deforming the liquid shape in an electrowetting cell, light can be steered and concentrated for solar energy applications. Here, the study demonstrates that the interface can be tilted vertically by applying a voltage to the side electrode faces. By sequentially applying a voltage to different electrode faces, the interface can be rotated 360° horizontally. Finally, the study demonstrates a 4.5° change of laser beam path with only a 0.2 refractive index difference of the liquids. The device has the potential to eliminate the disadvantages associated with bulky mechanical tracking devices. A thin array of electrowetting cells can be placed on a Fresnel lens and direct the sunlight towards the Fresnel lens for concentration without extra tracking. The electrowetting cell array can also be used to steer and concentrate solar energy onto a concentrated photovoltaic cell directly.

We outline a laser array beam forming concept that is capable of meeting the laser power requirements of Breakthrough Starshot, a concept aimed at propelling spacecraft to extremely high velocities via laser radiation pressure. Our laser beam forming design offers solutions to the required laser power, optical radiance, beam steering, beam focusing, and atmospheric turbulence compensation specifications. The design consists of a large array of hexagonally close-packed optical modules. Each module contains a collimating lens illuminated by a single fiber from a coherent array of fiber amplifiers. Beam steering is accomplished by transverse micromotion of the fiber amplifier tip illuminating each collimating optic, coupled with a phase shift applied to each module by an electrooptic modulator. Overall array focus is performed by adjusting the transverse and longitudinal fiber positions of each module. Thus, by simply manipulating the position of the fiber feeds of each module and applying the appropriate phase shifts, the beam shape of the entire array can be conditioned to meet the focusing and tracking requirements of the Breakthrough Starshot concept. The same hardware can compensate for the atmospheric aberrations of piston, tilt, and quadratic curvature. For our strawman design, we calculate the overall Strehl ratio reduction of the entire array resulting from incomplete array fill factors, errors in the array phasing, finite laser bandwidth and atmospheric turbulence to be 0.36.

Bimorph deformable mirror with 63 electrodes on 20 mm aperture is discussed. Methods of dividing all round electrode into sectors with a square of 2-4 mm2 are described. Results of flat-top beam formation by means of 50 mm bimorph deformable mirror with 48 electrodes and 20 mm miniature bimorph mirror with 27 electrodes are presented.

We propose a novel method for generating axial cosine structured light by using phase-only spatial light modulator. We implemented axial cosine structured light using holographic technique. The computer generates double concentric annular slits with different radius, a prism phase is applied on the slits to tilts the beam that incidents on the slits away from the optical axis. Different annular beam produce Bessel beams with different axial wave vectors, axial cosine structured light can be obtained from the interference between two Bessel beams. The period and phase of axial cosine structured light can be adjusted by adjusting the radius and the initial phase difference of the double concentric annular beams. We theoretically and experimentally verify that the method can effectively generate axial cosine structured light.

We present a novel optical device which interchanges two orthogonal directions in the cross-section of a beam. The optical prism is composed of six flat faces and has particular edge angles. The beam passing through the component is totally reflected at right angles inside the prism and flipped diagonally at the exit with respect to the entrance. When a line beam is incident to the device, the beam is segmented step by step at the first side face and combined on the other side. The overall shape of the line beam is maintained at the exit, but the segments of the line beam are flipped. The narrow axis of the line beam at the exit has the divergence angle corresponding to the long axis at the entrance. The component is also useful to focus beams from linear laser diode array with asymmetric divergence angles. Compared to the other beam transformation systems, the suggested device has advantages of easy fabrication, coating-free and no energy loss on reflective surfaces.

We present an experimental scheme to calculate the inner product of two arbitrary scalar optical fields. The scheme is based on using an interferometer to generate superpositions of the optical fields with a relative phase difference between the two fields. The intensity observed permits the calculation of the inner product using numerical integration. The experimental results obtained for the inner product of a few common optical fields are presented along with comparison with simulations.