High-Q silicon photonic crystal cavity for enhanced optical nonlinearities

Abstract

We fabricate and experimentally characterize an H0 photonic crystal slab nanocavity with a design optimized for maximal quality factor, Q = 1.7 × 106. The cavity, fabricated from a silicon slab, has a resonant mode at λ = 1.59 μm and a measured Q-factor of 400 000. It displays nonlinear effects, including high-contrast optical bistability, at a threshold power among the lowest ever reported for a silicon device. With a theoretical modal volume as small as V = 0.34(λ/n)3, this cavity ranks among those with the highest Q/V ratios ever demonstrated, while having a small footprint suited for integration in photonic circuits.

Single photons from dissipation in coupled cavities

“…The real input power can be estimated to 50 × P in = 778 pW when taking into account a conservative value for the in-coupling efficiency [33]. This value is about 30 times smaller than the typical input power required for single photon operation with quantum dots [4].…”

Efficient continuous-wave nonlinear frequency conversion in high-Q gallium nitride photonic crystal cavities on silicon

“…This is due to the transparency of the GaN layer that is multi-modal at the harmonic wavelength, combined with the symmetry of the χ (2) tensor. The generated harmonic originating from the bulk nonlinearity is propagating and appears to be strongly scattered upon interaction with the PhC lattice.…”

“…The dominant components of the second-order susceptibility tensor of wurtzite GaN (C 6v point-group symmetry) are χ (2) zzz followed by χ (2) zxx/zyy and χ (2) xxz/yyz (and their respective permutations), 17 of which χ (2) zxx/zyy can be exploited with the quasi transverse-electric nature of the fundamental cavity mode, for the c-axis oriented GaN layer. The induced polarization hence follows the spatial profile of the resonant fundamental mode.…”

“…While there is a clear trade-off theoretically between the coupling efficiency and Q-factor for a given cavity design, the upper limit on the Q-factor that is imposed by loss channels, given the disorder figure of current fabrication technology, makes room for introducing improved far-field coupling to enhance nonlinear processes without sacrificing the experimentally achievable light confinement. In contrast to commonly used semiconductors, the transparency of GaN for all participating frequencies of χ (2) and χ (3) processes enables the utilization of compact diode lasers as pumps. The platform's capability for integration and the fact that the demonstrated nonlinearity has been achieved under continuous-wave operation is promising for on-chip low-power applications, particularly integrated optical networks that can benefit from the generation of non-classical light states, frequency upconversion for improved near-IR detection, and all-optical switching to support emerging optical computing architectures.…”

Advances in diamond nanofabrication for ultrasensitive devices

“…In summary, ideally, an integrated nanoscale mechanics or photonics platform in diamond should mimic the planar technologies which have been developed in SOI since the mid1990s 99,100 , all operating at fiber optic telecommunication wavelength, λ~1550 nm. Despite the progress in diamond nanofabrication, there are still fundamental challenges to be overcome regarding their employment in some of the foreseen applications, particularly in the quantum technology domain where the nanofabricated structures need to have integrated color centers.…”