Broadband high-Q multimode silicon concentric racetrack resonators for widely tunable Raman lasers

Abstract

Multimode silicon resonators with ultralow propagation losses for ultrahigh quality (Q) factors have been attracting attention recently. However, conventional multimode silicon resonators only have high Q factors at certain wavelengths because the Q factors are reduced at wavelengths where fundamental modes and higher-order modes are both near resonances. Here, by implementing a broadband pulley directional coupler and concentric racetracks, we present a broadband high-Q multimode silicon resonator with average loaded Q factors of 1.4 × 106 over a wavelength range of 440 nm (1240–1680 nm). The mutual coupling between the two multimode racetracks can lead to two supermodes that mitigate the reduction in Q factors caused by the mode coupling of the higher-order modes. Based on the broadband high-Q multimode resonator, we experimentally demonstrated a broadly tunable Raman silicon laser with over 516 nm wavelength tuning range (1325–1841 nm), a threshold power of (0.4 ± 0.1) mW and a slope efficiency of (8.5 ± 1.5) % at 25 V reverse bias.

Review of Broadband Metamaterial Absorbers: From Principles, Design Strategies, and Tunable Properties to Functional Applications

“…In the field of micro‐nano optics, a crucial measure of performance of resonators, [ 166 ] filters, [ 167 ] transparent ceramics, [ 168 ] and other devices is the dimensionless quality factor ( Q ‐factor), which represents the ratio of resonant frequency to the full width at half maximum (FWHM) and describes the relationship between the resonance bandwidth and its center frequency according to a theoretical equation. [ 125 ] $$\[ \begin{array}{*{20}{c}}{Q = \frac{{{f_0}}}{{\Delta f}}}\end{array} \]$$where f 0 refers to the center frequency of the resonant peak and Δ f represents the frequency interval between FWHM.…”

“…In the field of micro-nano optics, a crucial measure of performance of resonators, [166] filters, [167] transparent ceramics, [168] and other devices is the dimensionless quality factor (Q-factor), which represents the ratio of resonant frequency to the full width at half maximum (FWHM) and describes the relationship between the resonance bandwidth and its center frequency according to a theoretical equation. [125] Q f f…”

An Introduction to Nonlinear Integrated Photonics Devices: Nonlinear Effects and Materials

“…In ref. [ 46 ], a new approach using multimode silicon concentric racetracks, allowing high Q factors to be maintained in every single FSR over a broad optical bandwidth, was presented. Based on this resonator, a widely tunable Raman lasing spanning from 1325 to 1841 nm was experimentally demonstrated [ 46 ].…”

“…This strategy gives rise to transparent crystallized glasses (glass-ceramics). The nonlinear optical properties of glasses have been used in several technological applications with a broad spectrum of phenomena, such as optical frequency conversion, optical solitons, phase conjugation, and Raman amplification [ 43 , 44 , 45 , 46 ].…”

Ultra-High-Q Racetrack Resonators on Thick SOI Platform Through Hydrogen Annealing Smoothing

“…A different configuration to avoid HOM excitation used MM concentric racetracks combined with a broadband directional coupler based on a pulley configuration demonstrating a Q-factor of 1.4 × 10 6 over a wavelength range from 1240 to 1680 nm. The two supermodes of the concentric waveguides had slightly detuned resonance wavelengths, which helps counteract the Q-factor deterioration due to coupling to HOMs at the fundamental mode resonances [16]. Another approach to achieve high Q-factors is to smoothen the sidewall roughness through different processing techniques.…”