Spatial light modulator

About: Spatial light modulator is a research topic. Over the lifetime, 9043 publications have been published within this topic receiving 130143 citations.

Optical encryption system with a binary key code

Abstract: A double-random-phase optical encryption system that uses a binary key code is proposed. The key code is generated as a binary computer-generated hologram. The binary key code can be displayed on a binary spatial light modulator (SLM) such as a ferroelectric liquid-crystal display. The use of a binary SLM enables us to renew the key at high speed. A joint transform correlator based on a photorefractive crystal in the Fourier domain is used to perform shift-invariant encryption and decryption. Computer simulations of the effects of using a binary encoded key code instead of a complex amplitude key code are shown. Preliminary optical experimental results are presented to demonstrate the effectiveness of the proposed system.

Wave front engineering for microscopy of living cells

Abstract: A new method to perform simultaneously three dimensional optical sectioning and optical manipulation is presented. The system combines a multi trap optical tweezers with a video microscope to enable axial scanning of living cells while maintaining the trapping configuration at a fixed position. This is achieved compensating the axial movement of the objective by shaping the wave front of the trapping beam with properly diffractive optical elements displayed on a computer controlled spatial light modulator. Our method has been validated in three different experimental configurations. In the first, we decouple the position of a trapping plane from the axial movements of the objective and perform optical sectioning of a circle of beads kept on a fixed plane. In a second experiment, we extend the method to living cell microscopy by showing that mechanical constraints can be applied on the dorsal surface of a cell whilst performing its fluorescence optical sectioning. In the third experiment, we trapped beads in a three dimensional geometry and perform, always through the same objective, an axial scan of the volume delimited by the beads.

Dual-source optical wavelength processor

Abstract: An optical signal manipulation system and, in particular a reconfigurable optical add/drop multiplexer for applications in WDM networks is disclosed. The system (100) includes an array of input and output ports (101-104) for carrying a series of optical signals to be manipulated, a polarisation manipulation element (115), such as a walk-off crystal, for spatially separating the series of optical signals into a first and a second group, a wavelength dispersion element (171), such as diffraction grating, for subsequently angularly dispersing by wavelength the first and second group of optical signals, and a wavelength processing means (180) for processing the spatially separated wavelengths. The wavelength processing means (180) may be a liquid crystal on silicon spatial light modulator having a plurality of independently addressable pixels for modifying the phase and/or amplitude of light passing through the modulator.

High-precision laser beam shaping using a binary-amplitude spatial light modulator

Abstract: We have achieved high-precision laser beam shaping by using a binary-amplitude spatial light modulator, a digital micromirror device (DMD), followed by an imaging telescope that contains a pinhole low-pass filter (LPF). An error diffusion algorithm was used to design the initial DMD pixel pattern based on the measured input beam profile. This pattern was iteratively refined by simulating the optically low-pass filtered DMD image and changing DMD pixels to lift valleys and suppress peaks. We noted the gap between the experimental result of 1.4% root-mean-square (RMS) error and the simulated result for the same DMD pattern of 0.3% RMS error. Therefore, we deemed it necessary to introduce iterative refinement based on actual measurements of the output image to further improve the uniformity of the beam. Using this method, we have demonstrated the ability to shape raw, non-spatially filtered laser beams (quasi-Gaussian beams) into beams with precisely controlled profiles that have an unprecedented level of RMS error with respect to the target profile. We have shown that our iterative refinement process is able to improve the light intensity uniformity to around 1% RMS error in a raw camera image for both 633 and 1064 nm laser beams. The use of a digital LPF on the camera image is justified in that it matches the performance of the pinhole filter in the experimental setup. The digital low-pass filtered results reveal that the actual optical beam profiles have RMS error down to 0.23%. Our approach has also demonstrated the ability to produce a range of target profiles as long as they have similar spatial-frequency content (i.e., a slowly varying beam profile). Circular and square cross-section flat-top beams and beams with a linear intensity variation within a circular and square cross section were produced with similarly low RMS errors. The measured errors were about twice the ultimate limit of 0.1% RMS error based on the number of binary DMD pixels that participate in the beam-formation process.

Surface micro-planarization for enhanced optical efficiency and pixel performance in SLM devices

Abstract: A method for enhancing the optical performance of a reflective spatial light modulator by micro-planarizing surfaces within the SLM, such as the reflective surface of each pixel, by gas-cluster-ion-beam bombardment.