Optical parametric oscillation in silicon carbide nanophotonics

Silicon carbide (SiC) is rapidly emerging as a leading platform for the implementation of nonlinear and quantum photonics. Here, we find that commercial SiC, which hosts a variety of spin qubits, possesses low optical absorption that can enable SiC integrated photonics with quality factors exceeding$107$. We fabricate multimode microring resonators with quality factors as high as 1.1 million, and observe low-threshold ($8.5±<#comment/>0.5mW$) optical parametric oscillation using the fundamental mode as well as optical microcombs spanning 200 nm using a higher-order mode. Our demonstration is an essential milestone in the development of photonic devices that harness the unique optical properties of SiC, paving the way toward the monolithic integration of nonlinear photonics with spin-based quantum technologies.

Authors:
; ; ; ; ; ;
Publication Date:
NSF-PAR ID:
10190285
Journal Name:
Optica
Volume:
7
Issue:
9
Page Range or eLocation-ID:
Article No. 1139
ISSN:
2334-2536
Publisher:
Optical Society of America
1. Thin-film lithium-niobate-on-insulator (LNOI) has emerged as a superior integrated-photonics platform for linear, nonlinear, and electro-optics. Here we combine quasi-phase-matching, dispersion engineering, and tight mode confinement to realize nonlinear parametric processes with both high efficiency and wide wavelength tunability. On a millimeter-long, Z-cut LNOI waveguide, we demonstrate efficient ($1900±<#comment/>500%<#comment/>W−<#comment/>1cm−<#comment/>2$) and highly tunable ($−<#comment/>1.71nm/K$) second-harmonic generation from 1530 to 1583 nm by type-0 quasi-phase-matching. Our technique is applicable to optical harmonic generation, quantum light sources, frequency conversion, and many other photonic information processes across visible to mid-IR spectral bands.
2. Materials with strong second-order ($χ<#comment/>(2)$) optical nonlinearity, especially lithium niobate, play a critical role in building optical parametric oscillators (OPOs). However, chip-scale integration of low-loss$χ<#comment/>(2)$materials remains challenging and limits the threshold power of on-chip$χ<#comment/>(2)$OPO. Here we report an on-chip lithium niobate optical parametric oscillator at the telecom wavelengths using a quasi-phase-matched, high-quality microring resonator, whose threshold power ($∼<#comment/>30µ<#comment/>W$) is 400 times lower than that in previous$χ<#comment/>(2)$integrated photonics platforms. An on-chip power conversion efficiency of 11% is obtained from pump to signal and idler fields at a pump power of 93 µW. The OPO wavelength tuning is achieved by varying the pump frequency and chip temperature. With the lowest power threshold among all on-chip OPOs demonstrated so far, as well as advantages including high conversion efficiency, flexibility in quasi-phase-matching, and device scalability, the thin-film lithium niobate OPO opens new opportunities for chip-based tunable classical and quantum light sources and provides a potential platform for realizing photonic neural networks.
3. Optical nonlinearity plays a pivotal role in quantum information processing using photons, from heralded single-photon sources and coherent wavelength conversion to long-sought quantum repeaters. Despite the availability of strong dipole coupling to quantum emitters, achieving strong bulk optical nonlinearity is highly desirable. Here, we realize quantum nanophotonic integrated circuits in thin-film InGaP with, to our knowledge, a record-high ratio of$1.5%<#comment/>$between the single-photon nonlinear coupling rate ($g/2π<#comment/>=11.2MHz$) and cavity-photon loss rate. We demonstrate second-harmonic generation with an efficiency of$71200±<#comment/>10300%<#comment/>/W$in the InGaP photonic circuit and photon-pair generation via degenerate spontaneous parametric downconversion with an ultrahigh rate exceeding 27.5 MHz/µW—an order of magnitude improvement of the state of the art—and a large coincidence-to-accidental ratio up to$1.4×<#comment/>104$. Our work shows InGaP as a potentially transcending platform for quantum nonlinear optics and quantum information applications.
4. Light carries both spin angular momentum (SAM) and orbital angular momentum (OAM), which can be used as potential degrees of freedom for quantum information processing. Quantum emitters are ideal candidates towards on-chip control and manipulation of the full SAM–OAM state space. Here, we show coupling of a spin-polarized quantum emitter in a monolayer$WSe2$with the whispering gallery mode of a$Si3N4$ring resonator. The cavity mode carries a transverse SAM of$σ<#comment/>=±<#comment/>1$in the evanescent regions, with the sign depending on the orbital power flow direction of the light. By tailoring the cavity–emitter interaction, we couple the intrinsic spin state of the quantum emitter to the SAM and propagation direction of the cavity mode, which leads to spin–orbit locking and subsequent chiral single-photon emission. Furthermore, by engineering how light is scattered from the WGM, we create a high-order Bessel beam which opens up the possibility to generate optical vortex carrying OAM states.
5. We demonstrate the DC-Kerr effect in plasma enhanced chemical vapor deposition (PECVD) silicon-rich nitride (SRN) and use it to demonstrate a third order nonlinear susceptibility,$χ<#comment/>(3)$, as high as$(6±<#comment/>0.58)×<#comment/>10−<#comment/>19m2/V2$. We employ spectral shift versus applied voltage measurements in a racetrack resonator as a tool to characterize the nonlinear susceptibilities of these films. In doing so, we demonstrate a$χ<#comment/>(3)$larger than that of silicon and argue that PECVD SRN can provide a versatile platform for employing optical phase shifters while maintaining a low thermal budget using a deposition technique readily available in CMOS process flows.