We propose a self-calibrating method for high-frequency response measurement of electro-optic phase modulators based on two-tone modulation. The method utilizes the electrical domain measurement of heterodyning spectrum between the two-tone modulation optical signal and the frequency-shifted optical carrier, and eliminates the need to correct the responsivity fluctuation in the photodetection. High-frequency modulation depth and half-wave voltages are measured and compared to those with the traditional optical spectrum analysis method in the experimental demonstration. The proposed method enables calibration-free and accurate frequency response measurement of electro-optic phase modulators by using high-resolution electrical spectrum analysis.

A Fourier domain mode locking (FDML) optoelectronic oscillator (OEO) based on stimulated Brillouin scattering (SBS) is proposed to generate complementary linearly chirped microwave waveform (LCMW) pairs with flexibly-reconfigurable frequency sweep range and excellent frequency sweep linearity. The FDML OEO involves an SBS-based dual-passband microwave photonic filter with its two passbands linearly and fast scanning in the opposite direction at an identical frequency sweep rate, which is realized by using a single laser source to obtain a fast frequency sweep probe light and a two-tone pump light through electro-optic modulation. A proof-of-concept experiment is carried out to demonstrate the proposed scheme. In the experiment, frequency-sweep-range-reconfigurable complementary LCMW pairs with period of 20.5 's are generated in the range of 5 GHz to 18 GHz, where the maximum time-bandwidth product and chirp rate are 82000 and ±0.195 GHz/μs, respectively. Most importantly, the frequency sweep linearity is measured to be 1.76%, which is much better than the results obtained in the existing FDML OEOs.

A wafer-level and high-efficiency radio frequency (RF) testing of a photonic device is highly desired in the fabrication and characterization of large-scale photonic integration circuits. In this work, we propose on-wafer probing kit designs, and demonstrate a damage-free, self-calibrated RF characterization of an integrated silicon photonic transceiver with a heterodyne mixing approach. Reduced or even free of fiber coupling off chip operation can be achieved with the on-wafer probing-kit to extract the frequency responses of broadband modulators and photodetectors in the photonic integration transceiver, with no requirement of electro-optical or opto-electrical calibration. A proof-of-concept probing kit is designed and fabricated with an on-chip electroabsorption modulator (EAM) and photodetectors by heterogeneously integrated III-V material on silicon substrate. On-wafer RF measurements with the self-calibration method are experimentally demonstrated with an accuracy analysis compared with the conventional swept-frequency method. The on-wafer and full-electrical test nature of the probing kit significantly advances performance monitoring of photonic integration circuits during chip fabrication, and promisingly offers predictable outcome and yield analysis before packaging.

An approach to generating periodic spiking and spiking cluster in a broadband nonlinear opto-electronic oscillator (OEO) is proposed and demonstrated. Through injecting a long-duration square-wave pulse train with a repetition frequency equal to an integral multiple of the free spectral range into the OEO with a high net gain, controllable spiking and spiking cluster oscillation can be achieved when the dual-drive Mach-Zehnder modulator (DDMZM) in the OEO is biased far away from its quadrature point. The proposed scheme is verified by both numerical simulation and experiment. The results indicate that, when the DDMZM in the OEO cavity is biased near its minimum transmission point, positive spiking train with nanosecond-level pulse width is excited by the rising edge of the injected square-wave pulse train. Through further enhancing the injection strength, uniformly-spaced positive spiking fills the high-level voltage duration of each injected square-wave pulse. Hence, spiking cluster oscillation is achieved. Benefiting from its controllability, this approach can be applied in ultra-wideband (UWB) communications, electronic countermeasures, spiking coding and high-speed neuromorphic computing.

An approach to characterizing the microwave performance of an electro-optic Mach-Zehnder modulator (MZM) is proposed based on photonic down-conversion sampling. Through low-speed sampling, the magnitude response of the MZM at the input microwave frequency is transferred to the duplicate component in the first Nyquist frequency range, and can be measured via low-frequency detection and spectrum analysis. A proof-of-concept experiment is carried out to demonstrate the feasibility of the proposed method, where magnitude-frequency response and half-wave voltage versus frequency of a commercial MZM in the frequency range of 0-40 GHz have been accurately measured under a sampling rate of 96.9 MS/s. Both simulation and experimental results indicate that the proposed method can be implemented without any extra calibration.

A photonic technique for microwave frequency measurement with flexible range and high resolution is proposed based on frequency-configurable pilot tones. The method extracts the remote unknown microwave frequency by measuring electrical power at two known pilot frequencies, avoiding dual-channel photodetection and broadband microwave power measurement over the whole interested frequency range. Moreover, it enables flexible measurement range by configuring two pilot frequencies. A proof-of-concept experiment is successfully demonstrated with the frequency range of 6-18.9 GHz and the resolution of 0.1 GHz.