Abstract
We report on single crystal diamond micro-disk resonators fabricated in bulk chemical vapor deposition diamond plates (3 mm × 3 mm × 0.15 mm) using a combination of deep reactive ion etching and Focused Ion Beam (FIB) milling. The resulting structures are micro-disks of few μm in diameter and less than 1 µm thick, supported by a square or diamond section pillar resulting from the multi-directional milling. Thin aluminum and chromium layers are used to ground the substrate, limit the ion implantation, and prevent edge rounding and roughening. FIB damage is then removed by a combination of hydrofluoric acid etching, oxygen plasma cleaning, and annealing at 500 °C for 4 h in air. We experimentally characterize the optical behavior of the devices by probing the transmission of a tapered fiber evanescently coupled to the micro-disk, revealing multiple resonances with a quality factor up to 5700 in the S- and C-band.
Highlights
Mechanical quality factors even at room temperature.[21]
The mechanical quality factor describes the coupling of the mechanical oscillator with the environment, and its product with the oscillation frequency is useful as a figure of merit that gives an indication on the thermal decoherence, i.e., the temperature limit at which the optomechanical interaction can exist
In the case of diamond, the micro-disk thickness has to be of the order of 300–400 nm to be a single-mode, a condition necessary to construct high-bandwidth integrated photonic circuits
Summary
Micro-disks can offer a high mechanical frequency and mechanical quality factor with a relatively simple fabrication scheme.[22,23] In the case of diamond, the micro-disk (and diamond waveguide) thickness has to be of the order of 300–400 nm to be a single-mode, a condition necessary to construct high-bandwidth integrated photonic circuits. For these thicknesses and micro-disk diameters of few micrometers, considering the diamond stiffness, the supported radial expansion mechanical oscillation mode (“breathing” mode) is in the 1-5 GHz range. Not based on the use of focused ion beams, have been proposed, including thinning and patterning of a diamond slab transferred on top of a sacrificial substrate,[29] or modifying the incidence angles of reactive ions to achieve suspended structures with a triangular cross section (with a Faraday cage or by tilting and rotating the sample in a reactive ion beam Etcher).[31,34,35] Microdisk resonators have been fabricated in single crystal diamond using a “quasi-isotropic” undercut using high power oxygen plasma with no RIE platen bias, forming an octagonal section support pillar due to the crystal symmetry of the diamond lattice.[32,36] With this method, optomechanical effects like optomechanically induced transparency were demonstrated,[8] allowing creating additional suspended
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