Rostislav V. Roussev

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Conventional single-photon detectors at communication wavelengths suffer from low quantum efficiencies and large dark counts. We present a single-photon detection system, operating at communication wavelengths, based on guided-wave frequency upconversion in a nonlinear crystal with an overall system detection efficiency (upconversion + detection) exceeding(More)
We demonstrate a four-user 10-Gb/s spectrally phasecoded optical code-division multiple-access system via nonlinear processing with ultralow power ( 30 fJ/bit). Full interference suppression is achieved in a time-slotted scheme without the need for chip-level coordination and synchronous detection. Performance degradation caused by pulse overlap between(More)
Efficient three-wave mixing devices have numerous applications, including wavelength conversion, dispersion compensation, and all-optical switching. Second-harmonic generation (SHG) is a useful diagnostic for near-degenerate operation of these devices. With buried waveguides formed in periodically poled lithium niobate by annealed and reverse proton(More)
We demonstrate ultrafast optical code-division multiple-access nonlinear waveform discrimination at 10 GHz with less than 1 mW coupled into a nonlinear periodically poled lithium niobate waveguide and greater than 20-dB contrast ratio between coded and uncoded waveforms. Excellent signal-to-noise is observed at the system receiver, pointing toward the(More)
Reconfigurable all-optical code translation are demonstrated in a spectrally phase-coded optical-code-division multiple-access (O-CDMA) testbed with an interference user. For both one-stage and two-stage code translations, less than 0.9-dB power penalties are induced at each code translation. Multistage code translations are investigated via simulation and(More)
We demonstrate a multi-user, 10Gb/s spectrally phase coded O-CDMA system with hybrid chip and slot-level timing coordination utilizing low power nonlinear processing. A new double Hadamard coding scheme is demonstrated to enable both chip-level timing coordination and full interference suppression without the need for synchronous detection.
We present a device to facilitate single-photon detection at communication wavelengths based on continuous-wave sum-frequency generation with an upconversion efficiency exceeding 90%. Sum-frequency generation in a periodically poled lithium niobate waveguide is used to upconvert signal photons to the near infrared, where detection can be performed(More)
We report 99% pump depletion in single-pass second-harmonic generation. Quasi-cw pulses at 1550 nm were frequency doubled in an annealed proton-exchanged waveguide formed in periodically poled lithium niobate. Measurements of pump depletion and second-harmonic generation agree with results from numerical integration of the coupled-mode equations that(More)
We propose several techniques to modulate the local amplitude of quasi-phase-matched (QPM) interactions in periodically poled lithium niobate waveguides and demonstrate apodization by using each of these techniques. When the hard edges are removed in the spatial profile of the nonlinear coupling, the sidelobes of the frequency tuning curves are suppressed(More)