422 Million Q Planar Integrated All-Waveguide Resonator with a 3.4 Billion Absorption Limited Q, Sub-MHz Linewidth and 3005 Finesse

Abstract

High Q optical resonators that are a key component for ultra-narrow linewidth lasers, frequency stabilization, precision spectroscopy and quantum applications. Integration of these resonators in a photonic waveguide wafer-scale platform is key to reducing their cost, size and power as well as sensitivity to environmental disturbances. However, to date, the intrinsic Q of integrated all-waveguide resonators has been relegated to below 150 Million for a non-etched waveguide resonator and 230 Million for a waveguide-coupled etched silica microresonator. Here, we report an all-waveguide Si3N4 resonator with an intrinsic Q of 422 Million and a 3.4 Billion absorption loss limited Q. The resonator linewidth measures at 453 kHz intrinsic linewidth, 906 kHz loaded linewidth with finesse of 3005. The corresponding linear loss of 0.060 dB/m is the lowest reported to date for an all-waveguide design with deposited upper cladding oxide. These are the highest intrinsic and absorption loss limited Q factors and lowest linewidth reported to date for a photonic integrated all-waveguide resonator. This level of performance is achieved through a careful reduction of scattering and absorption loss components and redeposition of a thin nitride layer. We quantify, simulate and measure the various loss contributions including scattering and absorption and describe a surface-state dangling bond absorption that we believe is passivated by the redeposited layer. In addition to the ultra-high Q and narrow linewidth, the resonator has a large optical mode area and volume, both critical for ultra-low laser linewidths and ultra-stable, ultra-low frequency noise reference cavities. These results demonstrate the performance of bulk optic and etched resonators can be realized in a photonic integrated solution, paving the way towards photonic integration compatible Billion Q cavities for precision scientific systems and applications such as nonlinear optics, atomic clocks, quantum photonics and high-capacity fiber communications systems on-chip.

Ultra-low loss quantum photonic circuits integrated with single quantum emitters

“…Regarding our passive photonic circuits, lower propagation losses may be achieved by employing blanket nitride growth, etch, and annealing techniques 64 , as well as transverse magnetic (TM) field designs 1 . At the same time, we anticipate that a variety of on-chip passive components already demonstrated in this platform, including spiral delay lines 65 , filters 66 , and couplers and switches 67 , can be further optimized for lower insertion losses.…”

Optically synchronized fibre links using spectrally pure chip-scale lasers

“…The individual photonic components of the OFS-PLL are readily integrated in silicon nitride (SiN) and heterogeneous silicon photonic (SiPh) platforms 54,58,59 with mW-tier BiCMOS electrical integrated circuits. Future work includes OFS-PLL implementations with heterogeneously integrated lasers as the SBS pump source 60 , waveguide integration of the reference cavities 41,61,62 , and co-location of the control electronics 49 to provide a fully integrated, low-power solution. Additional modifications to the OFS-PLL architecture include adding a frequency pull-in stage to extend the capture range of the optical phase lock and operating with both polarizations to enable polarization diverse sensing and dual polarization optical communications.…”

Frequency-to-Time Mapping Technique for Direct Spectral Characterization of Biphoton States From Pulsed Spontaneous Parametric Processes

“…It is important to note that the FTM technique is merely considered for spectral characterization of broad spectra such as biphoton state spectra of ultra-short pulsed-excited parametric processes and for sources where the temporal width of the photons' wave packets fall below the temporal resolution of the detection system. In particular, spectral characterization of photon pairs generated in high Q-factor (Q > 1000000) resonators (Puckett et al, 2021) as well as from continuous wave-driven parametric processes are practicable neither with FTM technique nor via the state-of-the-art programmable filters, owing to the ultra-narrow line-widths of the modes that fall in the order of kHz. These systems are better characterized directly in the time-domain.…”