Yanyang Zhou

On-Chip Optical Power Monitor Using Periodically Interleaved P-N Junctions Integrated on a Silicon Waveguide

We investigate the photocurrent generation with surface-state absorption effect in a silicon waveguide integrated with periodically interleaved p-n junctions. Due to the high electric field (~5 × 105 V/cm) and large depletion area coverage in the waveguide, our device can collect more photocurrent than regular p-i-n and p-n structures. The responsivity of our device is optical power dependent with a higher value at a lower power level. The measured 3-dB bandwidth of the frequency response is 11.5 GHz. Although its responsivity is low compared to that of III-V and Ge photodiodes, its simple fabrication and compatibility with all-silicon photonic devices makes it suitable as on-chip optical power monitors.

Linearity Measurement and Pulse Amplitude Modulation in a Silicon Single-Drive Push–Pull Mach–Zehnder Modulator

We characterize the modulation linearity of a silicon Mach-Zehnder modulator with a single-drive push-pull configuration. The 3-dB electro-optic bandwidths of the modulator are 15 and 32 GHz at 0 and 6 V reverse biases, respectively. The best spurious-free dynamic ranges (SFDRs) for the second-order harmonic distortion and the third-order intermodulation distortion are measured to be 97.7 dB·Hz2/3 and 85.9 dB·Hz1/2. The experimental measurement demonstrates that such a drive scheme can effectively reduce the modulation nonlinearity, especially the second harmonic distortion. Multi-level pulse amplitude modulation (PAM) is achieved using this high-linearity modulator with PAM-2,3,4,5 at a symbol rate of 40 Gbaud/s and PAM-8 at a symbol rate of 25 Gbaud/s.

Optimized Silicon QPSK Modulator With 64-Gb/s Modulation Speed

We demonstrate a compact silicon quadrature phase-shift keying (QPSK) modulator consisting of two nested Mach-Zehnder interferometers with a size of 4.5-mm². The V₁₁ · L of the modulator is 1.4 V · cm with an insertion loss of 8 dB. In addition, 64-Gb/s QPSK modulation is achieved with an error vector magnitude (EVM) of 24.4% and bit error rate (BER) of 2.1 × 10^-5 at the received optical power of -10 dBm after the device and an EVM of 31.7% and BER of 8.4 × 10^-4 at the received optical power of 0 dBm after 10-km single-mode fiber transmission. The estimated power consumption is 7.1 pJ/bit for the 64-Gb/s QPSK modulation.

All-Silicon Waveguide Avalanche Photodetectors With Ultrahigh Gain-Bandwidth Product and Low Breakdown Voltage

We investigate the avalanche effect in 250 μm long silicon waveguides integrated with periodically interleaved p-n junctions. The surface state absorption is enhanced by reducing the waveguide width. Upon a bias voltage of -5.9 V, the measured responsivity is 2.33 A/W with a dark current of 0.78 μA. The avalanche gain is 284 and the 3-dB bandwidth is 3.6 GHz, leading to an ultrahigh gain-bandwidth product of 1.02 THz. The avalanche photocurrent is stable with time below -6 V when ~1 mW on-chip optical power is launched. The photodetector has a linear response to optical power and can be readily integrated with other silicon photonic devices.

Linearity Characterization of a Dual–Parallel Silicon Mach–Zehnder Modulator

We report a high-linearity wideband dual-parallel silicon Mach-Zehnder modulator (MZM). This modulator consists of two carrier-depletion-based MZMs with a single-drive push-pull traveling wave electrode configuration. An analytic model is established to investigate the linearity property of the modulator. The measurement results show the modulator can effectively suppress third-order harmonics and third-order intermodulation distortions, with improved modulation linearity, compared to a single MZM.

50 Gb/s silicon QPSK modulator with single-drive push-pull traveling wave electrodes design

We demonstrate a silicon QPSK modulator consisting of two nested Mach-Zehnder interferometers with 3.5 mm long traveling-wave electrodes. 50 Gb/s QPSK modulation is achieved with power consumption of 9.3 pJ/bit.

Optimized silicon MZI modulators for 50 Gbit/s OOK and 40 Gbit/s BPSK modulation

We report 50Gb/s On-Off keying (OOK) and 40Gb/s binary phase shift keying (BPSK) modulation in a single-drive push-pull silicon Mach-Zehnder modulator with optimized segmented electrode design. The measured modulation efficiency (Vπ·Lπ) is ~1.77 V·cm at 4.0 V reverse bias and the electro-optic (EO) 3-dB bandwidth exceeds 30 GHz at 6.0 V reverse bias.

Design of traveling wave electrode for high-speed silicon modulators

We design a traveling wave electrode to drive carrier-depletion-based silicon modulators. By optimizing the electrode on top of the active region and the connection transmission line, the impedance can be matched to 50 Ohm. The 3-dB bandwidth of the modulator can be up to 40 GHz, mainly limited by the velocity mismatch.

Linearity characterization of a dual-parallel Mach-Zehnder modulator

We achieve highly-linear modulation by using two parallel simultaneously-driven Mach-Zehnder modulators. Measurement results show that the third-order intermodulation distortion is suppressed significantly.

Microwave Signal Processing using High Speed Silicon Optical Modulators

We review our recent progress on the high-speed silicon optical modulators for microwave signal processing applications. Various functions including microwave phase shift, frequency multiplication and linear modulation have been realized.