Weiqiang Wang

Dual-pump Kerr micro-cavity optical frequency comb with varying FSR spacing

In this paper, we demonstrate a novel dual-pump approach to generate robust optical frequency comb with varying free spectral range (FSR) spacing in a CMOS-compatible high-Q micro-ring resonator (MRR). The frequency spacing of the comb can be tuned by an integer number FSR of the MRR freely in our dual-pump scheme. The dual pumps are self-oscillated in the laser cavity loop and their wavelengths can be tuned flexibly by programming the tunable filter embedded in the cavity. By tuning the pump wavelength, broadband OFC with the bandwidth of >180 nm and the frequency-spacing varying from 6 to 46-fold FSRs is realized at a low pump power. This approach could find potential and practical applications in many areas, such as optical metrology, optical communication, and signal processing systems, for its excellent flexibility and robustness.

Raman self-frequency-shift of soliton crystal in a high index doped silica micro-ring resonator [Invited]

High index doped silica glass exhibiting low loss property and CMOS compatibility is a promising material in nonlinear optics. In this work, mode-locked soliton crystals (SCs) are demonstrated in a high-Q (>106) micro-ring resonator (MRR) made in this platform. The asymmetric spectra of SCs are numerically investigated and interpreted as the combined impact of Raman self-frequency shift (RSFS) and the wavelength-dependent loss. By precisely comparing the experimental and simulated spectra based on the perturbed Lugiato-Lefever equation (LLE), the Raman shock time is inferred to be at the range of 2.5 fs to 2.7 fs for this material.

Ultra-high Q one-dimensional hybrid PhC-SPP waveguide microcavity with large structure tolerance

Abstract A photonic crystal – surface plasmon-polaritons hybrid transverse magnetic mode waveguide based on a one-dimensional optical microcavity is designed to work in the communication band. A Gaussian field distribution in a stepping heterojunction taper is designed by band engineering, and a silica layer compresses the mode field to the subwavelength scale. The designed microcavity possesses a resonant mode with a quality factor of 1609 and a modal volume of 0.01 cubic wavelength. The constant period and the large structure tolerance make it realizable by current processing techniques.

Compact cross-dispersion device based on a prism and a plane transmission grating

Abstract This paper presents a cross-dispersion prism-grating device using a plane transmission grating attached directly to a prism, which is different from traditional cross-dispersion grating-prism systems that are based on the reflection grating. Unlike conventional direct-vision grism or constant-dispersion grism in which both the prism and grating have the same dispersion direction, for this device the dispersion directions of the prism and grating are different. The analytical expressions for the cross-dispersion of this device are derived in detail and the formulas of the footprint of the dispersed spectra are given. The numerical results and ray-tracing simulations by ZEMAX are shown. The device provides a compact, small-sized and broadband cross-dispersion device used for the medium resolution spectrometer.

Frequency-degenerate parametric generation through IFWM effect in nanowaveguides

We investigate highly efficient frequency-degenerate parametric generation through inverse four-wave-mixing (IFWM) in silicon nanowaveguides, which exhibits distinctly from traditional FWM phenomenon and manifests itself as a unique process producing signal and idler photon pairs with frequencies at the center of two pumps. The influences of dispersion, nonlinear coefficient and frequency detuning on the IFWM process are numerically analyzed in detail. On this basis, the optimal condition for high gain IFWM and the nanowaveguide with high nonlinearity and large normal dispersion are proposed. These results substantiate the feasibility of such frequency-degenerate parametric generation in CMOS-compatible integrated platforms, which could find important potential in signal-processing systems for photonics networks and entangled qubits generation for quantum optics.