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In recent decades, holographic technology has made significant progress with the development of novel hologram generation methods and three-dimensional rendering devices. Nevertheless, the substantial size of holographic data presents a significant challenge to its practical applications and thus necessitates the implementation of an efficient coding solution. In this study, we evaluate the efficiency of various coding tools within the state-of-the-art video coding standard, Versatile Video Coding, for encoding video of computer-generated phase-only hologram. Specifically, we examine the coding performance of transform/in-loop filter/screen-content coding tools. Through extensive encoding experiments and various statistical analyses, we investigated the limitations of existing standard codecs that do not account for the unique signal characteristics of phase-only holograms (POHs). The effects of coding artifacts on the visual quality of numerical reconstructions rendered from compressed POHs are also analyzed in detail. These comprehensive performance evaluations will provide valuable insights for developing efficient coding strategies for POH videos.

We report on the demonstration of top emitting AlGaN tunnel junction deep ultraviolet (UV) light emitting didoes (LEDs) operating at ∼267 nm. We show, both theoretically and experimentally, that the light extraction efficiency can be enhanced by nearly a factor of two with the incorporation of AlGaN nanowire photonic crystal structures. A peak wall-plug efficiency (WPE) ∼3.5% and external quantum efficiency (EQE) ∼5.4% were measured for AlGaN LEDs directly on-wafer without any packaging. This work demonstrates a viable path for achieving high efficiency deep UV LEDs through the integration of AlGaN planar and nanoscale structures.

We present a computational framework for efficient optimization-based "inverse design" of large-area "metasurfaces" (subwavelength-patterned surfaces) for applications such as multi-wavelength/multi-angle optimizations, and demultiplexers. To optimize surfaces that can be thousands of wavelengths in diameter, with thousands (or millions) of parameters, the key is a fast approximate solver for the scattered field. We employ a "locally periodic" approximation in which the scattering problem is approximated by a composition of periodic scattering problems from each unit cell of the surface, and validate it against brute-force Maxwell solutions. This is an extension of ideas in previous metasurface designs, but with greatly increased flexibility, e.g. to automatically balance tradeoffs between multiple frequencies or to optimize a photonic device given only partial information about the desired field. Our approach even extends beyond the metasurface regime to non-subwavelength structures where additional diffracted orders must be included (but the period is not large enough to apply scalar diffraction theory).

We show that iterative solution of Maxwell's equations using the finite-difference frequency-domain method can be significantly accelerated by using a Schur complement domain decomposition method. We account for the improvement by analyzing the spectral properties of the linear systems resulting from the use of the domain decomposition method.

We theoretically investigate three-dimensional plasmonic waveguide-cavity structures, built by side-coupling stub resonators that consist of plasmonic coaxial waveguides of finite length, to a plasmonic coaxial waveguide. The resonators are terminated either in a short or an open circuit. We show that the properties of these waveguide-cavity systems can be accurately described using a single-mode scattering matrix theory. We also show that, with proper choice of their design parameters, three-dimensional plasmonic coaxial waveguide-cavity devices and two-dimensional metal-dielectric-metal devices can have nearly identical transmission spectra. Thus, three-dimensional plasmonic coaxial waveguides offer a platform for practical implementation of two-dimensional metal-dielectric-metal device designs.

We introduce a simple method to accelerate the convergence of iterative solvers of the frequency-domain Maxwell's equations for deep-subwavelength structures. Using the continuity equation, the method eliminates the high multiplicity of near-zero eigenvalues of the operator while leaving the operator nearly positive-definite. The impact of the modified eigenvalue distribution on the accelerated convergence is explained by visualizing residual vectors and residual polynomials.

We theoretically and experimentally investigated a novel walk-off-compensation method for efficient ultraviolet beam generation. Through theoretical investigation, we described in detail how the power of a generated UV beam can be enhanced by the method; thus, we obtained a brief expression for the output power which has a prediction error of about 30%. In addition, we found that the beam quality can also be enhanced using this method. Through experiments using an alpha barium borate crystal as a walk-off compensator, we found that the power of the generated ultraviolet beam increased 1.9 times.

An optical scheme for speckle suppression using two or three partially coherent beams in a projection system is proposed. Diffractive optical elements (DOE) placed in the intermediate image plane create several beams carrying the image to a screen. Transparent plates of different thicknesses are placed in the Fourier plane of the projective lens and used for beam decorrelation. The coherence matrix algorithm for speckle suppression is used to calculate the speckle contrast ratio. It is shown that for a small decorrelation length and using the same maximum thickness of the transparent plates, two partially coherent beams would provide better suppression than three beams with different diffraction orders. However, for a large decorrelation length, the three beam setup provides better speckle suppression for all three colors examined with a suppression coefficient close to theoretical limits. Verification of speckle suppression using three-beam decorrelation is reported.

We have demonstrated the bandwidth control of a Ti-diffused periodically poled LiNbO(3) (Ti:PPLN) Solc filter by a temperature-gradient-control technique. Up to 2.8 nm of filtering bandwidth was achieved with a simple temperature-gradient-control technique in a 78-mm-long of Ti:PPLN waveguide, which has a 0.2 nm filtering bandwidth at an uniform temperature. We have also analyzed the experimental results with the theoretical calculation which is derived from the codirectional coupled mode equations.

We propose and demonstrate a tunable Q-switched erbium doped fiber laser with a digitally controlled micro-mirror array device. The tunable and pulsed output of the laser was achieved by the pixelated spatial modulation of the micro-mirror array. The wavelength tuning from 1530 nm to 1555 nm was shown with wavelength selectivity of ~0.1 nm and the pulsed operation was accomplished with 130 Hz repetition rate.

All-optical AND and NAND gates have been demonstrated in a Ti-diffused periodically poled LiNbO(3) channel waveguide which has two second-harmonic phase-matching peaks by cascaded sum-frequency-generation/difference-frequency-generation (cSFG/DFG) and sum-frequency-generation (SFG) processes. The conversion efficiency of signal to idler (AND gate signal) was approximately 0 dB in cSFG/DFG process. In the second SFG process, more than 15 dB extinction ratio between signal and dropped signal (NAND gate signal) has been observed.

We propose a novel technique to add new degrees of freedom in fiber optic coupler devices. Micro-optical waveguide (MOW) on a microactuating platform (MAP) structure has been proposed and experimentally implemented using fiber waveguides, where the coupling characteristics of MOW are mechanically varied by precise axial stress control by MAP. As an application of the proposed structure, we mounted the coupling zone of fused taper coupler array on a MAP to demonstrate a novel reconfigurable 1x4 wavelength selective optical switching function. Robust mechanical tuning among output ports of a four-channel demultiplexer was realized by precise elongation control of the taper region in serially cascaded fused fiber couplers. Simultaneous reconfigurable wavelength routing and switching functions were demonstrated among four channels in 1.5-microm coarse WDM transmission window. We report the principle, design concept, and the performances of the proposed device structure along with its potential in reconfigurable fiber optics.

We propose a new type of all-fiber device for inter-band router using a novel hybrid waveguide-MEMS technology. Both continuous and discrete band-routing functions are realized by precise twist control over the fused coupling region, which results in pi phase shift between the output ports. Experimentally we demonstrate inter-band routing functions between O and C-band as well as between E and L-band with a low insertion loss, wide bandwidth of operation, high channel isolation and fast response.