Topic
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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TL;DR: It is shown that high-speed QPSK, 8PSK.
Abstract: We review and summarize several 100G per channel high-capacity transmission systems enabled by advanced technologies such as multilevel modulation format, new low-loss and large effective area fiber, hybrid EDFA/Raman amplification, and digital coherent detection technologies. We show that high-speed QPSK, 8PSK, 8QAM, and 16QAM can all be generated using commercially available optical modulators using only binary electrical drive signals through novel synthesis methods, and that all of these modulation formats can be detected using digital coherent detection. We also show our latest research results on 400 Gb/s and 1 Tb/s per channel by using orthogonal DWDM transmission technologies.
144 citations
Patent•
25 Jan 2000TL;DR: In this paper, a chemical mechanical polishing apparatus includes two optical systems which are used serially to determine polishing endpoints, one consisting of a first light source to generate a first-light beam which impinges on a surface of the substrate, and a second sensor to measure light reflected from the surface of a substrate.
Abstract: A chemical mechanical polishing apparatus includes two optical systems which are used serially to determine polishing endpoints The first optical system includes a first light source to generate a first light beam which impinges on a surface of the substrate, and a first sensor to measure light reflected from the surface of the substrate to generate a measured first interference signal The second optical system includes a second light source to generate a second light beam which impinges on a surface of the substrate and a second sensor to measure light reflected from the surface of the substrate to generate a measured second interference signal The second light beam has a wavelength different from the first light beam
144 citations
TL;DR: The diffraction efficiency of near-sinusoidal gratings written on the device is of the order of 30%, which is close to theoretical maximum, and a comparison between the experimental results and the theoretical analysis shows good agreement.
Abstract: An optically addressed parallel-aligned nematic-liquid-crystal spatial light modulator is developed for applications in optical information processing and interferometry. Its performance, including diffraction efficiency, is measured, and a theoretical analysis of diffraction efficiency is performed. A comparison between the experimental results and the theoretical analysis shows good agreement. The diffraction efficiency of near-sinusoidal gratings written on the device is of the order of 30%, which is close to theoretical maximum.
144 citations
TL;DR: In this paper, the traveling wave electrodes are laterally shifted periodically to reverse the direction of the applied electric field within the optical waveguide which exactly compensates for the polarity reversal caused by the microwave-optical walkoff.
Abstract: We propose and analyze a new technique for achieving velocity match between the traveling wave electrical drive and guided optical signal for modulators in substrates for which there is an inherent mismatch. The traveling wave electrodes are laterally shifted periodically to reverse the direction of the applied electric field within the optical waveguide which exactly compensates for the polarity reversal caused by the microwave-optical walkoff. Consequently, the electrooptically induced phase shifts of each section add in phase and several sections can be used to reduce the required drive voltage at the design frequency. This artificial velocity-matching technique moves the mismatch-limited bandwidth to an arbitrarily high design frequency. In addition, we extend the new concept of phase reversal and the previously suggested technique of intermittent interaction by proposing electrode structures with large inactive to active aspect ratios. This generalization provides increased flexibility for manipulating the total available bandwidth to, for example, allow efficient modulation by a train of arbitrarily short electrical pulses. These techniques are ideally suited for several proposed integrated optic devices, including picosecond samplers and gates, which require strong overmodulation at a single high frequency.
143 citations
TL;DR: In this article, a novel GaAs/AlGaAs coupled quantum well structure, consisting of two 46 A wells separated by a 11.5 A barrier, was embedded in a leaky waveguide.
Abstract: A novel GaAs/AlGaAs coupled quantum well structure, consisting of two 46 A wells separated by a 11.5 A barrier, was embedded in a leaky waveguide. Polarization anisotropy and quantum‐confined Stark effect absorption changes are observed, and a 14:1 modulator is demonstrated operating at the peak of the first light‐hole transition. Although the lowest energy transitions behave as predicted by tunneling resonance calculations, higher energy states exhibit unusual behavior due to valence‐band mixing.
143 citations