On-chip diamond Raman laser

Abstract

Synthetic single-crystal diamond has recently emerged as a promising platform for Raman lasers at exotic wavelengths due to its giant Raman shift, large transparency window and excellent thermal properties yielding a greatly enhanced figure-of-merit compared to conventional materials [1, 2, 3]. To date, diamond Raman lasers have been realized using bulk plates placed inside macroscopic cavities [3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13], requiring careful alignment and resulting in high threshold powers (~W-kW). Here we demonstrate an on-chip Raman laser based on fully-integrated, high quality-factor, diamond racetrack microresonators embedded in silica. Pumping at telecom wavelengths, we show Stokes output discretely tunable over a ~100nm bandwidth around 2-μm with output powers >250 μW, extending the functionality of diamond Raman lasers to an interesting wavelength range at the edge of the mid-infrared spectrum [14]. Continuous-wave operation with only ~85 mW pump threshold power in the feeding waveguide is demonstrated along with continuous, mode-hop-free tuning over ~7.5 GHz in a compact, integrated-optics platform.Diamond serves as a compelling material platform for Raman lasers operating over a wide spectrum due to its superlative Raman frequency shift (~40 THz), large Raman gain (~10 cm/GW @ ~1-μm wavelength) and ultra-wide transparency window (from UV (>220nm) all the way to THz, except for a slightly lossy window from ~2.6 -6 μm due to multiphonon-induced absorption) [1,15]. Furthermore, the excellent thermal properties afforded by diamond (giant thermal conductivity of ~1800 W/m/K @ 300K and low thermo-optic coefficient of ~10 -5 /K) [1,2] along with negligible birefringence [3,15] make it an ideal material for high-power Raman lasing with greatly reduced thermal lensing effects [1,3].The availability of CVD-grown, high-quality polished, single-crystal diamond plates has enabled the development of bulk Raman lasers using macroscopic optical cavities across the UV [6], visible [4, 5], near-infrared [7, 8, 9, 10, 11, 12] and even mid-infrared [13] regions of the optical spectrum. Although showing great performance with large output powers (many Watts) [12] and near quantum-limited conversion efficiencies [5,9], most operate in pulsed mode in order to attain the very high pump powers required to exceed the Raman lasing threshold [5,6,11,12]. Demonstration of continuous-wave diamond Raman lasing has been challenging, with very few reports [3,7,8]. Bulk cavity systems also require precise alignment and maintenance of optical components for the laser to function robustly.

Mid-infrared integrated photonics on silicon: a perspective

“…Despite the advances and several follow-up theoretical investigations [90][91][92], mid-IR Raman lasing based on an on-chip Si platform has not yet been experimentally realized. As an alternative to Si, Raman lasing near 2.0-μm wavelength with an estimated internal quantum efficiency of 12% was achieved in diamond micro-resonators fabricated by transferring a diamond film onto an oxide-coated Si substrate [93]. In this case, the large Stokes shift in diamond (40 THz) versus that of Si (15.6 THz) facilitates first-order wavelength transition from telecom bands to the mid-IR range without resorting to the less efficient cascaded Raman scattering.…”

Fiber-Coupled Diamond Quantum Nanophotonic Interface

“…Together, recent efforts in quantum science and nanoscale engineering of diamond have resulted in the demonstration of a solid-state single-photon switch based on a single silicon-vacancy (SiV) color center embedded in a diamond PCC, as well as observation of entanglement between two SiVs implanted in a single diamond waveguide [12]. As diamond nanophotonics continues to enable advances in other disciplines (including non-linear optics [34,35] and optomechanics [36,37]), the demand for scalable technology necessitates moving beyond isolated devices, to fully integrated on-chip nanophotonic networks in which waveguides route photons between optical cavities [38]. Moreover, for applications involving single photons, such as quantum nonlinear optics with diamond color centers [12,22], efficient off-chip optical coupling schemes are necessary to provide seamless transition of on-chip photons into commercial single mode optical fibers [39][40][41][42].…”

Design and low-temperature characterization of a tunable microcavity for diamond-based quantum networks

“…Finally, the membrane is bonded to the plane mirror by van der Waals forces. 27 We first study the cavity modes by recording transmission spectra as a function of cavity length using broadband excitation from a supercontinuum laser (see Figure 1(c)). From these spectra, we extract the frequency of the fundamental modes of the cavity.…”