Two-dimensional Spatial Light Research Articles

Three-dimensional weight-accumulation algorithm for generating multiple excitation spots in fast optical stimulation

We report here an algorithm for calculating a hologram to be employed in a high-access speed microscope for observing sensory-driven synaptic activity across all inputs to single living neurons in an intact cerebral cortex. The system is based on holographic multi-beam generation using a two-dimensional phase-only spatial light modulator to excite multiple locations in three dimensions with a single hologram. The hologram was calculated with a three-dimensional weighted iterative Fourier transform method using the Ewald sphere restriction to increase the calculation speed. Our algorithm achieved good uniformity of three dimensionally generated excitation spots; the standard deviation of the spot intensities was reduced by a factor of two compared with a conventional algorithm.

Analysis of fabricating arbitrary nanoscale patterns by LSPP direct writing lithography with two-dimensional metal hole-array

We propose to use two-dimensional metal hole-array (TMH) and spatial light modulator (SLM) technology to construct a parallel direct-writing system. SLM and movable platform are used to control the system for realizing multi-beam parallel scanning exposure to fabricate arbitrary patterns. In this system TMH is the key component which focuses the incident light beams into light spots in the photoresist by exciting local surface plasmon polariton (LSPP). Parameters of TMH are optimized to improve the focusing efficiency and transmission depth of the light spots. Theoretical analysis and numerical simulations show that the feature size and transmission depth can reach sub-80nm and 90nm, respectively, by an optimized TMH, which is feasible for parallel direct writing lithography.

Two-dimensional phase-only spatial light modulators for dynamic phase and amplitude pulse shaping

We consider a two-dimensional liquid crystal spatial light modulator (SLM) for femtosecond pulse shaping. Novel shaping schemes enabling a drastic speed increase (about four orders of magnitude as compared with conventional liquid-crystal SLM-based pulse shapers) and complex (phase and amplitude) femtosecond pulse shaping are discussed and experimentally demonstrated. In the first case, while a horizontal resolution of 1920 addressable pixels provided superior fidelity for generating complex waveforms, scanning across the vertical dimension (1080 pixels) has been used to facilitate an update rate in excess of 100 kHz. In the second case, we use the pixel count redundancy in the vertical direction and encode a spectrally-dependent diffraction grating for modulation of both spectral phases and amplitudes.

Liquid crystal-based optical time delay units for phased array antennas

Novel two-dimensional (2-D) spatial light modulator (SLM)-based optical time delay units (OTDU's) using freespace/solid optics and fiber delays are introduced for phased array antenna and wideband signal processing applications. In particular, the mature nematic liquid crystal (NLC) SLM technology is considered for the proposed architectures. A 1/spl times/2 optical switch is demonstrated using a parallel-rub birefringent-mode NLC cell, a bulk optics cube polarizing beamsplitter, and a sheet polarizer. Switch measurements taken at 633 nm show a >3400:1 or >35 dB output port optical isolation. The 1/spl times/2 NLC switch is used to build a 1-bit, 3.33-ns-duration, free-space OTDU using mirrors and total internal reflection corner prisms. The unit demonstrated a >30 dB optical (or >60 dB electrical) signal-to-noise ratio for both delay and no-delay positions. A 1500 pixel NLC SLM is built, and a 128:1 or 21 dB on/off isolation is demonstrated limited by the digital drive electronics of thin-film transistor (TFT)-based pixel control. >

Contrast ratio improvement for the two-dimensional magneto-optic spatial light modulator

The contrast ratio for the two-dimensional magneto-optic spatial light modulator can be increased by using simple spatial filtering techniques or by adding a light-blocking layer.

Free-space folded-path optical programmable logic array

A new method to realize a medium-scale, free-space optical programmable logic array is proposed. By using either a two-dimensional optical spatial light modulator or an array of one-dimensional spatial light modulators inside a lens-based multiple-beam-path cavity, an array of optical multiple-variable logic product terms is generated. This device, together with a programmable multiple-variable OR matrix, can be used to implement any Boolean combinatorial logic operations. For an optical binary combinatorial logic computation, the proposed method efficiently uses three-dimensional space and optical elements. Preliminary experimental results obtained using an inexpensive liquid-crystal television are included.

Optical systems for efficient triple-matrix-product processing

Three different optical systems are developed for efficient evaluation of a triple-matrix product of the form [U][G][V]. One system uses a purely space-integrating architecture, whereas the other two use hybrid time-and space-integrating architectures. Each of these three systems has a distinct format for input [using one-dimensional (1-D)and two-dimensional (2-D) spatial light modulators) and output (using either 1-D or 2-D time-integrating detector arrays or high-bandwidth single-element detectors) devices, thus permitting a trade-off between parameters such as speed and dynamic range. Potential applications for these systems include image data compression and orthogonal transforms of coefficient matrices encountered in linear systems analysis.