422 Million intrinsic quality factor planar integrated all-waveguide resonator with sub-MHz linewidth

Abstract

High quality-factor (Q) optical resonators are a key component for ultra-narrow linewidth lasers, frequency stabilization, precision spectroscopy and quantum applications. Integration in a photonic waveguide platform is key to reducing cost, size, power and sensitivity to environmental disturbances. However, to date, the Q of all-waveguide resonators has been relegated to below 260 Million. Here, we report a Si3N4 resonator with 422 Million intrinsic and 3.4 Billion absorption-limited Qs. The resonator has 453 kHz intrinsic, 906 kHz loaded, and 57 kHz absorption-limited linewidths and the corresponding 0.060 dB m−1 loss is the lowest reported to date for waveguides with deposited oxide upper cladding. These results are achieved through a careful reduction of scattering and absorption losses that we simulate, quantify and correlate to measurements. This advancement in waveguide resonator technology paves the way to all-waveguide Billion Q cavities for applications including nonlinear optics, atomic clocks, quantum photonics and high-capacity fiber communications.

2022 Roadmap on integrated quantum photonics

“…Tapering from single-to multi-mode waveguides for straight sections can drastically reduce this. A different approach is to interface silicon with a different material such as SiN, where a lower index contrast means better propagation losses that can be pushed down to <0.1 dB m −1 [26]. Another important loss mechanism in silicon is two-photon absorption (TPA).…”

Visible light photonic integrated Brillouin laser

“…We predict that with the continued increase in S1 photon number up to the S2 threshold and with pump filtering, the fundamental linewidth can be reduced to ~2 Hz. Further improvements will require lowering the visible light loss, by exploring additional silica deposition processing techniques 60 and different waveguide modes for lasing. Our side-wall scattering loss models 60 suggest a significant improvement of 3×–4× is possible if the TM0 mode is used instead of TE0 mode.…”

“…Further improvements will require lowering the visible light loss, by exploring additional silica deposition processing techniques 60 and different waveguide modes for lasing. Our side-wall scattering loss models 60 suggest a significant improvement of 3×–4× is possible if the TM0 mode is used instead of TE0 mode. Such a loss reduction will linearly translate to a lower threshold and a smaller fundamental noise limit but will require careful design of couplers to suppress the TE0 mode to avoid crosstalk.…”

High-Q-Factor Tunable Silica-Based Microring Resonators

“…Though a 3.7 × 10 7 Q factor was obtained, the fabrication process is more complex. An ultrahigh Q factor of 4.22 × 10 8 SiN MRR was demonstrated in [10]. The ultralarge radius of 11.789 mm limits its application.…”

“…Owing to the compact footprint and functional versatility, optical microresonators have attracted much attention in many fields, including optical filters [1], sensors [2,3], and nonlinear optics [4]. Microresonator devices with a high Q factor were designed and demonstrated on different material platforms, such as silicon-on-insulator (SOI) [5][6][7], silicon nitride (SiN) [8][9][10], indium phosphide (InP)-based planar lightwave circuits (PLCs) [11][12][13], polymer-based PLCs [3,14,15], and silica-based PLCs [16]. Among them, benefitting from low loss, miniaturization, scalability, and high fiber-coupling efficiency, silica-based PLCs devices show great potential in optics integration and commercial field [17][18][19].…”