Minhao Pu

Nonlinear properties of and nonlinear processing in hydrogenated amorphous silicon waveguides

We propose hydrogenated amorphous silicon nanowires as a platform for nonlinear optics in the telecommunication wavelength range. Extraction of the nonlinear parameter of these photonic nanowires reveals a figure of merit larger than 2. It is observed that the nonlinear optical properties of these waveguides degrade with time, but that this degradation can be reversed by annealing the samples. A four wave mixing conversion efficiency of + 12 dB is demonstrated in a 320 Gbit/s serial optical waveform data sampling experiment in a 4 mm long photonic nanowire.

Widely tunable microwave phase shifter based on silicon-on-insulator dual-microring resonator

We propose and demonstrate tunable microwave phase shifters based on electrically tunable silicon-on-insulator microring resonators. The phase-shifting range and the RF-power variation are analyzed. A maximum phase-shifting range of 0-600 degrees is achieved by utilizing a dual-microring resonator. A quasi-linear phase shift of 360 degrees with RF-power variation lower than 2dB and a continuous 270 degrees phase shift without RF-power variation at a microwave frequency of 40GHz are also demonstrated.

Ultra-high-speed optical serial-to-parallel data conversion by time-domain optical Fourier transformation in a silicon nanowire

We demonstrate conversion from 64 × 10 Gbit/s optical time-division multiplexed (OTDM) data to dense wavelength division multiplexed (DWDM) data with 25 GHz spacing. The conversion is achieved by time-domain optical Fourier transformation (OFT) based on four-wave mixing (FWM) in a 3.6 mm long silicon nanowire. A total of 40 out of 64 tributaries of a 64 × 10 Gbit/s OTDM-DPSK data signal are simultaneously converted with a bit-error rate (BER) performance below the 2 × 10(-3) FEC limit. Using a 50 m long highly nonlinear fiber (HNLF) for higher FWM conversion efficiency, 43 tributaries of a 64 × 10 Gbit/s OTDM-OOK data signal are converted with error-free performance (BER<10(-9)).

Tunable complex-valued multi-tap microwave photonic filter based on single silicon-on-insulator microring resonator

A complex-valued multi-tap tunable microwave photonic filter based on single silicon-on-insulator microring resonator is presented. The degree of tunability of the approach involving two, three and four taps is theoretical and experimentally characterized, respectively. The constraints of exploiting the optical phase transfer function of a microring resonator aiming at implementing complex-valued multi-tap filtering schemes are also reported. The trade-off between the degree of tunability without changing the free spectral range and the number of taps is studied in-depth. Different window based scenarios are evaluated for improving the filter performance in terms of the side-lobe level.

One-to-six WDM multicasting of DPSK signals based on dual-pump four-wave mixing in a silicon waveguide

We present WDM multicasting based on dual-pump four-wave mixing in a 3-mm long dispersion engineered silicon waveguide. One-to-six phase-preserving WDM multicasting of 10-Gb/s differential phase-shift-keying (DPSK) data is experimentally demonstrated with bit-error rate measurements. All the six multicast signals show error-free performance with power penalty less than 3.8 dB.

Efficient frequency comb generation in AlGaAs-on-insulator

The combination of nonlinear and integrated photonics has recently seen a surge with Kerr frequency comb generation in micro-resonators as the most significant achievement. Efficient nonlinear photonic chips have myriad applications including high speed optical signal processing, on-chip multi-wavelength lasers, metrology, molecular spectroscopy, and quantum information science. Aluminium gallium arsenide (AlGaAs) exhibits very high material nonlinearity and low nonlinear loss when operated below half its bandgap energy. However, difficulties in device processing and low device effective nonlinearity made Kerr frequency comb generation elusive. Here, we demonstrate AlGaAs-on-insulator as a nonlinear platform at telecom wavelengths. Using newly developed fabrication processes, we show high-quality-factor (Q>100,000) micro-resonators with integrated bus waveguides in a planar circuit where optical parametric oscillation is achieved with a record low threshold power of 3 mW and a frequency comb spanning 350 nm is obtained. Our demonstration shows the huge potential of the AlGaAs-on-insulator platform in integrated nonlinear photonics.The combination of nonlinear and integrated photonics enables Kerr frequency comb generation in stable chip-based micro-resonators. Such a comb system will revolutionize applications, including multi-wavelength lasers, metrology, and spectroscopy. Aluminum gallium arsenide (AlGaAs) exhibits very high material nonlinearity and low nonlinear loss. However, difficulties in device processing and low device effective nonlinearity made Kerr frequency comb generation elusive. Here, we demonstrate AlGaAs-on-insulator as a nonlinear platform at telecom wavelengths with an ultra-high device nonlinearity. We show high-quality-factor (Q>105) micro-resonators where optical parametric oscillations are achieved with milliwatt-level pump threshold powers, which paves the way for on-chip pumped comb generation.

Optical waveform sampling and error-free demultiplexing of 1.28 Tbit/s serial data in a silicon nanowire

We experimentally demonstrate 640 Gbit/s and 1.28 Tbit/s serial data optical waveform sampling and 640-to-10 Gbit/s and 1.28 Tbit/s-to-10 Gbit/s error-free demultiplexing using four-wave mixing in a 300nm×450nm×5mm silicon nanowire.

Silicon chip based wavelength conversion of ultra-high repetition rate data signals

We report on all-optical wavelength conversion of 160, 320 and 640 Gbit/s line-rate data signals using four-wave mixing in a 3.6 mm long silicon waveguide. Bit error rate measurements validate the performance within FEC limits.

Low-loss high-confinement waveguides and microring resonators in AlGaAs-on-insulator

AlGaAs is a promising material for integrated nonlinear photonics due to its intrinsic high nonlinearity. However, the challenging fabrication of deep etched AlGaAs devices makes it difficult to realize high-performance devices such as low-loss dispersion engineered waveguides and high-quality microring resonators. Here, we report a process to make high-quality AlGaAs-on-insulator (AlGaAsOI) wafers where high confinement waveguides can be realized. Using optimized patterning processes, we fabricated AlGaAsOI waveguides with propagation losses as low as 1 dB/cm and microring resonators with quality factors up to 350,000 at telecom wavelengths. Our demonstration opens new prospects for AlGaAs devices in integrated nonlinear photonics.

320 Gb/s phase-transparent wavelength conversion in a silicon nanowire

All-optical wavelength conversion for a 320 Gb/s RZ-DPSK signal is demonstrated based on four wave mixing in a silicon nanowire. BER better than 10−9 is achieved for the wavelength converted RZ-DPSK signal.