Cavity-Enhanced Raman Scattering for In Situ Alignment and Characterization of Solid-State Microcavities

Abstract

We report cavity-enhanced Raman scattering from a single-crystal diamond membrane embedded in a highly miniaturized fully-tunable Fabry-Pérot cavity. The Raman intensity is enhanced 58.8fold compared to the corresponding confocal measurement. The strong signal amplification results from the Purcell effect. We show that the cavity-enhanced Raman scattering can be harnessed as a narrowband, high-intensity, internal light-source. The Raman process can be triggered in a simple way by using an optical excitation frequency outside the cavity stopband and is independent of the lateral positioning of the cavity mode with respect to the diamond membrane. The strong Raman signal emerging from the cavity output facilitates in situ mode-matching of the cavity mode to single-mode collection optics; it also represents a simple way of measuring the dispersion and spatial intensity-profile of the cavity modes. The optimization of the cavity performance via the strong Raman process is extremely helpful in achieving efficient cavity-outcoupling of the relatively weak emission of single color-centers such as nitrogen-vacancy centers in diamond or rare-earth ions in crystalline hosts with low emitter density.

Cryogenic platform for coupling color centers in diamond membranes to a fiber-based microcavity

“…Concerning the diamond membrane, a new generation of samples has shown reduced surface roughness values down to rms = 1 nm , which is close to state-of-the-art roughness values reported from 0.3 nm to about 1 nm [32,44,64]. Using an advanced application technique, based on the controlled transfer of the membrane using a focused ion beam (FIB) device allows for a cleaner and improved bonding, effectively increasing Q c with the incorporated membrane.…”

Widely-tunable, doubly-resonant Raman scattering on diamond in an open microcavity

“…We tune the mirror separation by applying a voltage to the piezo using a highly-stable voltage source (Basel Precision Instruments SP 927). Background photoluminescence (PL) from the diamond acts as an internal light source and couples to the different resonator modes [33]. Figure 1 (c) displays a PL spectrum collected through the top mirror.…”

“…1 (a)) [37][38][39][40][41][42]. The microcavity is formed by two mirror-coated fused silica substrates, one of which contains an array of spherical micromirrors fabricated via laser ablation [43] enabling efficient coupling to a single free-space mode [33,44]. The radii of curvature of these micromirrors are ∼ 10 µm resulting in a beam waist of ∼ 1 µm.…”

“…640 nm) as a pump source. The operation wavelength range of the cavity is given by the reflective stopband of the DBR, which we determine using a white-light transmission measurement [33]. Figure 1 (c) displays the stopband of the planar bottom mirror which is centered around λ c,bot = 625 nm; the reflectivity is more than 99% over a bandwidth of ∼ 100 THz.…”

“…diamond Raman laser, namely a highly miniaturized Fabry-Perot cavity [33]. Such microcavities, sometimes referred to as open microcavities, offer high Q/V ratios and thereby promote strong light-matter interactions [34,35].…”