Rostislav V. Roussev

Highly efficient second-harmonic generation in buried waveguides formed by annealed and reverse proton exchange in periodically poled lithium niobate

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 exchange, we demonstrate what is believed to be the highest normalized conversion efficiency (150%/W cm(2)) for SHG in the 1550-nm communications band reported to date.

Highly efficient single-photon detection at communication wavelengths by use of upconversion in reverse-proton-exchanged periodically poled LiNbO 3 waveguides

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 46% at 1.56 microm. This system consists of a fiber-pigtailed reverse-proton-exchanged periodically poled LiNbO3 waveguide device in conjunction with a silicon-based single-photon counting module.

Four user, 2.5 Gb/s, spectrally coded O-CDMA system demonstration using low power nonlinear processing

This paper describes the demonstration of 2.5-Gb/s four-user optical-code-division-multiple-access (OCDMA) system operating at bit-error rate /spl les/10/sup -11/ utilizing programmable spectral phase encoding, an ultrasensitive (/spl sim/200 fJ/b) periodically poled lithium-niobate-waveguide nonlinear waveform discriminator and 10G Ethernet receiver. A comprehensive description of this ultra-short-pulse spectral phase-coded OCDMA system is presented. On the subsystem level, two key component technologies, namely, femtosecond encoding/decoding and low-power high-contrast nonlinear discrimination, have been developed and characterized. At the system level, data for the four-user OCDMA system operating at 2.5 Gb/s for binary as well as multilevel code families are described.We demonstrate for the first time 2.5 Gb/s four user O-CDMA operation at /spl les/10/sup -11/ BER utilizing programmable spectral phase encoding, an ultrasensitive (<0.4 pJ/bit) PPLN-waveguide nonlinear waveform discriminator and 10 G Ethernet receiver.

Periodically poled lithium niobate waveguide sum-frequency generator for efficient single-photon detection at communication wavelengths

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 efficiently by use of silicon avalanche photodiodes.

Observation of 99% pump depletion in single-pass second-harmonic generation in a periodically poled lithium niobate waveguide

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 describe the process.

Amplitude modulation and apodization of quasi-phase-matched interactions

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 by 13 dB or more, compared with a uniform grating, consistent with theoretical predictions. The sidelobe-suppressed gratings are useful for frequency conversion devices in optical communication systems to minimize interchannel cross talk, while the amplitude modulation techniques in general have potential uses in applications that require altering the tuning curve shapes.

160-Gb/s OTDM transmission using integrated all-optical MUX/DEMUX with all-channel modulation and demultiplexing

This letter provides the first report of 160-Gb/s optical time-division-multiplexed transmission with all-channel independent modulation and all-channel simultaneous demultiplexing. By using a multiplexer and a demultiplexer based on periodically poled lithium niobate and semiconductor optical amplifier hybrid integrated planar lightwave circuits, 160-km transmission is successfully demonstrated.

44-ns Continuously Tunable Dispersionless Optical Delay Element Using a PPLN Waveguide With Two-Pump Configuration, DCF, and a Dispersion Compensator

This letter presents an optically controlled, continuously tunable, dispersionless optical delay element in fiber based on a selective wavelength converter using a periodically poled lithium-niobate waveguide with two-pump configuration, dispersion-compensated fiber, and a dispersion compensator. Optical phase information is preserved in this technique, and there is no fundamental limitation on pulsewidth or bit rate. A Continuous optical delay up to 44-ns is shown for 10-Gb/s nonreturn-to-zero applications, which is equal to a 440-bit slot

Low-power high-contrast coded waveform discrimination at 10 GHz via nonlinear processing

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 practicability of nonlinear waveform discrimination in a system environment.

Squeezing in a LiNbO3 integrated optical waveguide circuit

We report on traveling-wave quadrature squeezing generated in an integrated optical circuit fabricated with periodicallypoled lithium niobate waveguides. The device integrates a secondharmonic-generation stage, waveguide couplers, spatial mode filters, and a degenerate-optical-parametric-amplification stage. The integrationpromises to create a low power, compact, and simple source of wideband squeezed light. -1 dB of squeezing is directly measured using 20 ps pulses with peak powers near 6W.