Pressure sensing with high-finesse monolithic buckled-dome microcavities.

We describe the use of on-chip buckled-dome Fabry-Perot microcavities as pressure sensing elements. These cavities, fabricated by a controlled thin-film buckling process, are inherently sealed and support stable optical modes (finesse >103), which are well-suited to coupling by single-mode fibers. Changes in external pressure deflect the buckled upper mirror, leading to changes in resonance wavelengths. Experimental shifts are shown to be in good agreement with theoretical predictions. Sensitivities as large as ∼1nm/kPa, attributable to the low thickness (<2µm) of the buckled mirror, and resolution ∼10Pa are demonstrated. We discuss potential advantages over traditional low-finesse, quasi-planar Fabry-Perot pressure sensors.

Monolithically integrated membrane-in-the-middle cavity optomechanical systems.

We describe curved-mirror Fabry-Perot cavities with embedded silicon nitride membranes, fabricated using a monolithic surface-micromachining process. The presence of the suspended membranes was confirmed by confocal microscopy, and their properties were verified through optical studies and thermomechanical calibration of mechanical/vibrational noise spectra measured at room temperature and atmospheric pressure. The cavities exhibit reflectance-limited finesse (F ∼ 103) and wavelength-scale mode volumes (VM ∼ 10·λ3). The short cavity length (L ∼ 2·λ) results in large optomechanical coupling, which is desirable for numerous applications in sensing and quantum information.

Liquid infiltration of monolithic open-access Fabry-Perot microcavities.

We describe a monolithic approach to fabricating large-scale arrays of high-finesse and low-mode-volume Fabry-Perot microcavities with open access to the air core. A stress-driven buckling self-assembly technique was used to form half-symmetric curved-mirror cavities, and a dry etching process was subsequently used to create micropores through the upper mirror. We show that the cavities retain excellent optical properties, with reflectance-limited finesse ∼2500 and highly predictable Laguerre-Gaussian modes. We furthermore demonstrate the ability to introduce liquids into the cavity region by microinjection through the pores. Applications in sensing, optofluidics, and cavity quantum electrodynamics are envisioned.

Cooperativity enhancement in buckled-dome microcavities with omnidirectional claddings.

We describe a theoretical study of dipole emitters inside buckled-dome Fabry-Perot cavities with Si/SiO2-based omnidirectional Bragg mirrors. The low penetration depth of the mirrors contributes to low mode volumes, potentially enabling large enhancement of spontaneous emission into moderate-quality-factor cavity modes. Furthermore, the omnidirectional mirrors can significantly inhibit background emission. For a representative cavity operating in a fundamental spatial mode regime at λ ~1550 nm, and an optimally located emitter, we predict simultaneous enhancement of emission into the cavity mode by ~120 and suppression of background emission by ~25, implying the potential for a cooperativity C ~1500. This is combined with Q ~103, significantly lower than is required to attain similar values of C without background inhibition, and thus implying better compatibility for broad line-width emitters.