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Optical modulator

About: Optical modulator is a research topic. Over the lifetime, 14068 publications have been published within this topic receiving 196932 citations.


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Patent
15 Oct 1998
TL;DR: In this article, a system for the production of a dynamic image for use in holography includes a light source (16) which travels via a liquid crystal modulator (18) placed in the path of the light source.
Abstract: A system for the production of a dynamic image for use in holography includes a light source (16) which travels via a liquid crystal modulator (18) placed in the path of the light source (16). The output of the LC modulator (18) passes modulated light through a lens array (22) which itself guides light to an optically addressed spatial light modulator (24). The resulting real image from the optically addressed spatial light modulator (24) may be used in holography. The addressing frame-rate of the liquid crystal modulator (18) is substantially greater than the frame-rate of the optically addressed spatial light modulator (24).

74 citations

Journal ArticleDOI
TL;DR: In this paper, an in-line fiber-optic intensity modulator using evanescent coupling from a fiber to a thin film of electro-Optic polymer deposited onto a fiber half coupler was proposed.
Abstract: An in-line fibre-optic intensity modulator is reported that uses evanescent coupling from a fibre to a thin film of electro-optic polymer deposited onto a fiber half coupler. Modulation depths up to 16 dB and low loss (0-6 dB) have been demonstrated. >

73 citations

Journal ArticleDOI
TL;DR: Numerical analysis revealed that the driving current for a given optical attenuation in a carrier-injection Ge waveguide device at a 1.95 μm wavelength can be approximately five times smaller than that in a Si device, enabling in-line carrier- injection Ge optical modulators based on free-carrier absorption.
Abstract: We present Ge rib waveguide devices fabricated on a Ge-on-insulator (GeOI) wafer as a proof-of-concept Ge mid-infrared photonics platform. Numerical analysis revealed that the driving current for a given optical attenuation in a carrier-injection Ge waveguide device at a 1.95 μm wavelength can be approximately five times smaller than that in a Si device, enabling in-line carrier-injection Ge optical modulators based on free-carrier absorption. We prepared a GeOI wafer with a 2-μm-thick buried oxide layer (BOX) by wafer bonding. By using the GeOI wafer, we fabricated Ge rib waveguides. The Ge rib waveguides were transparent to 2 μm wavelengths and the propagation loss was found to be 1.4 dB/mm, which may have been caused by sidewall scattering. We achieved a negligible bend loss in the Ge rib waveguide, even with a 5 μm bend radius, owing to the strong optical confinement in the GeOI structure. We also formed a lateral p-i-n junction along the Ge rib waveguide to explore the capability of absorption modulation by carrier injection. By injecting current through the lateral p-i-n junction, we achieved optical intensity modulation in the 2 μm band based on the free-carrier absorption in Ge.

73 citations

Journal ArticleDOI
TL;DR: An experimental correlator using the Light-Mod magnetooptic spatial light modulator (SLM) devices for real-time modulation of both input images and Fourier plane filters has been constructed and demonstrated and is in good agreement with computer simulations based on the FFT.
Abstract: An experimental correlator using the Light-Mod magnetooptic spatial light modulator (SLM) devices for real-time modulation of both input images and Fourier plane filters has been constructed and demonstrated. Results are in good agreement with computer simulations based on the FFT. The experiment, results and comparison with theory are briefly described here. The optical system is diagrammed in Fig. 1. A five-lens design was used to reduce system length by a factor of ~ 4 compared with that required for a classical two-lens coherent correlator configuration. The Light-Mod devices were 48 X 48-element arrays. Polarizers following each Light-Mod, necessary for proper operation, are not shown. Proper scal­ ing of the Fourier transform pattern on the second (filter) device required an effective focal length of 1219 mm for the first transform lens determined by the wavelength (632.8 nm) and Light-Mod element spacing (0.127 mm). The first (input) Light-Mod was operated in the binary amplitude modulation (on-off) mode, while the second (filter) device was operated as a binary (0-180°) phase modulator. Thus the filter device comprised an electrically programmable binary phase-only filter (BPOF). Properties of this type filter have been reported recently. Both devices are con­ trolled by an Apple He computer, and filters or input images can be introduced into the system in a few milliseconds each. A 128X 128-point FFT model was used to predict results and to generate BPOFs to drive the filter Light-Mod. To generate filters, 128 X 128 transforms were averaged over 3 X 3 subareas, and the BPOF phase value was set according to the sign of the real part of the transform, as previously reported. Figure 2(a) shows the input pattern used in the experiments. Figure 2(b) shows predicted correlation re­ sults using the input of Fig. 2(a) and a BPOF calculated for the X pattern. Figure 3 shows the experimental correlation result ob­ tained with the input and filter patterns corresponding to the computer model result of Fig. 2(b). The figure shows video monitor photos taken at two different brightness set­ tings while the correlation pattern was read out with a cam­ era tube. Excellent agreement with theory is apparent. Figure 3(b), taken with the lower brightness setting, indi­ cates the two brightest peaks corresponding to the position of the two X characters in the input plane. Figure 3(a) shows the theoretically predicted cross-correlation structure (between 0 inputs and X filter) at the lower right position. Absence of such a structure at the upper left position is attributed to nonuniform input plane illumination. Experi­ mental results also were likely degraded by the defects pres­ ent in both Light-Mods comprising approximately two lines which were permanently set in one magnetic state in each device. The results reported here demonstrate the potential for useful real-time correlation systems based on the use of Fig. 1. Diagram of Light-Mod correlator system.

73 citations

Journal ArticleDOI
TL;DR: This work presents a fast and easy technique for measuring the beam propagation ratio, M(2), of laser beams using a spatial light modulator, based on digitally simulating the free-space propagation of light, thus eliminating the need for the traditional scan in the propagation direction.
Abstract: We present a fast and easy technique for measuring the beam propagation ratio, M2, of laser beams using a spatial light modulator. Our technique is based on digitally simulating the free-space propagation of light, thus eliminating the need for the traditional scan in the propagation direction. We illustrate two approaches to achieving this, neither of which requires any information of the laser beam under investigation nor necessitates any moving optical components. The comparison with theoretical predictions reveals excellent agreement and proves the accuracy of the technique.

73 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202342
2022154
2021166
2020289
2019311
2018325