Trung D. Vo

Integrated spatial multiplexing of heralded single-photon sources

The non-deterministic nature of photon sources is a key limitation for single-photon quantum processors. Spatial multiplexing overcomes this by enhancing the heralded single-photon yield without enhancing the output noise. Here the intrinsic statistical limit of an individual source is surpassed by spatially multiplexing two monolithic silicon-based correlated photon pair sources in the telecommunications band, demonstrating a 62.4% increase in the heralded single-photon output without an increase in unwanted multipair generation. We further demonstrate the scalability of this scheme by multiplexing photons generated in two waveguides pumped via an integrated coupler with a 63.1% increase in the heralded photon rate. This demonstration paves the way for a scalable architecture for multiplexing many photon sources in a compact integrated platform and achieving efficient two-photon interference, required at the core of optical quantum computing and quantum communication protocols.

Instantaneous frequency measurement system using optical mixing in highly nonlinear fiber.

A broadband photonic instantaneous frequency measurement system utilizing four-wave mixing in highly nonlinear fiber is demonstrated. This new approach is highly stable and does not require any high-speed electronics or photodetectors. A first principles model accurately predicts the system response. Frequency measurement responses from 1 to 40 GHz are demonstrated and simple reconfiguration allows the system to operate over multiple bands.

Photonic chip based transmitter optimization and receiver demultiplexing of a 1.28 Tbit/s OTDM signal

We demonstrate chip-based Tbaud optical signal processing for all-optical performance monitoring, switching and demultiplexing based on the instantaneous Kerr nonlinearity in a dispersion-engineered As(2)S(3) planar waveguide. At the Tbaud transmitter, we use a THz bandwidth radio-frequency spectrum analyzer to perform all-optical performance monitoring and to optimize the optical time division multiplexing stages as well as mitigate impairments, for example, dispersion. At the Tbaud receiver, we demonstrate error-free demultiplexing of a 1.28 Tbit/s single wavelength, return-to-zero signal to 10 Gbit/s via four-wave mixing with negligible system penalty (< 0.5 dB). Excellent performance, including high four-wave mixing conversion efficiency and no indication of an error-floor, was achieved. Our results establish the feasibility of Tbaud signal processing using compact nonlinear planar waveguides for Tbit/s Ethernet applications.

Ultracompact all-optical XOR logic gate in a slow-light silicon photonic crystal waveguide.

We demonstrate an ultracompact photonic chip-based all-optical exclusive-OR (XOR) gate via four-wave mixing in a dispersion-engineered silicon photonic crystal waveguide. We achieve error-free operation for 40 Gbit/s differential phase shift keying (DPSK) signals at 30mW powers.

Repetition-rate-selective, wavelength-tunable mode-locked laser at up to 640 GHz

We demonstrate a tunable passively mode-locked fiber laser with a selectable repetition rate of up to 640 GHz. The mode-locking mechanism is based on dissipative four-wave mixing in combination with a programmable optical processor as the spectral filter. We achieve up to 20 nm wavelength tunability and present mode-locked operation at repetition rates between 40 and 640 GHz. Measurements of the power spectra using a cross-phase modulation technique confirm the mode locking.

Silicon nanowire based radio-frequency spectrum analyzer.

We demonstrate a silicon nanowire based radio-frequency spectrum analyzer capable of characterizing ultrahigh speed optical data. Through measurement of 640GBit/s on-off-keyed data we show that although nonlinear loss affects device efficiency, free-carrier dispersion is negligible.

Simultaneous multi-impairment monitoring of 640 Gb/s signals using photonic chip based RF spectrum analyzer

We report the first demonstration of simultaneous multi-impairment monitoring at ultrahigh bitrates using a THz bandwidth photonic-chip-based radio-frequency (RF) spectrum analyzer. Our approach employs a 7 cm long, highly nonlinear (gamma approximately 9900 /W/km), dispersion engineered chalcogenide planar waveguide to capture the RF spectrum of an ultrafast 640 Gb/s signal, based on cross-phase modulation, from which we numerically retrieve the autocorrelation waveform. The relationship between the retrieved autocorrelation trace and signal impairments is exploited to simultaneously monitor dispersion, in-band optical signal to noise ratio (OSNR) and timing jitter from a single measurement. This novel approach also offers very high OSNR measurement dynamic range (> 30 dB) and is scalable to terabit data rates.

Photonic chip-based all-optical XOR gate for 40 and 160 Gbit/s DPSK signals

We demonstrate a photonic chip-based all-optical exclusive-OR (XOR) gate for phase-encoded optical signals via four-wave mixing in a highly nonlinear, dispersion-engineered chalcogenide (As2S3) planar waveguide. We achieve error-free, XOR operation for 40 Gbit/s differential phase shift keying (DPSK) optical signals with no power penalty. The effectiveness and broad bandwidth operation of our approach is highlighted by implementing an XOR gate for 160 Gbit/s DPSK signals.

Terahertz bandwidth RF spectrum analysis of femtosecond pulses using a chalcogenide chip

We report the first demonstration of the use of an RF spectrum analyser with multi-terahertz bandwidth to measure the properties of femtosecond optical pulses. A low distortion and broad measurement bandwidth of 2.78 THz (nearly two orders of magnitude greater than conventional opto-electronic analyzers) was achieved by using a 6 cm long As(2)S(3) chalcogenide waveguide designed for high Kerr nonlinearity and near zero dispersion. Measurements of pulses as short as 260 fs produced from a soliton-effect compressor reveal features not evident from the pulses optical spectrum. We also applied an inverse Fourier transform numerically to the captured data to re-construct a time-domain waveform that resembled pulse measurement obtained from intensity autocorrelation.

Silicon-Chip-Based Real-Time Dispersion Monitoring for 640 Gbit/s DPSK Signals

We demonstrate silicon-chip-based instantaneous chromatic dispersion monitoring (GVD) for an ultrahigh bandwidth 640 Gbit/s differential phase-shift keying (DPSK) signal. This monitoring scheme is based on cross-phase modulation in a highly nonlinear silicon nanowire. We show that two-photon absorption and free-carrier-related effects do not compromise the GVD monitoring performance, making our scheme a reliable on-chip CMOS-compatible, all-optical, and real-time impairment monitoring approach for up to Terabit/s DPSK signals.