Pressure sensing with high-finesse monolithic buckled-dome microcavities

Abstract

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 &gt; 10 3 ), 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 ∼ 1 n m / k P a , attributable to the low thickness ( &lt;<!-- 2 µ m ) of the buckled mirror, and resolution ∼ 10 P a are demonstrated. We discuss potential advantages over traditional low-finesse, quasi-planar Fabry–Perot pressure sensors.

All-Optical, Air-Coupled Ultrasonic Detection of Low-pressure Gas Leaks and Observation of Jet Tones in the MHz Range

“…We previously conducted several studies on the optical properties of these devices, including their suitability for quantum electrodynamics due to the high finesse (~10 3 -10 4 ) and small mode volumes (as low as ~1.5 λ 3 ) routinely obtained [17][18][19], their applications in microfluidics as open-access cavities for liquids [20], and their ability to be fabricated with large birefringence and polarization mode non-degeneracy [21]. More recently, we demonstrated that our devices function as extremely sensitive optomechanical sensors for both static pressure differentials [22] and ultrasonic signals in air and water [16,23]. Notably, the ultrasonic force sensitivity is one or more orders of magnitude lower than other air-coupled ultrasound sensors, with a bandwidth spanning several MHz [24][25][26].…”

Ultrasonic spectroscopy of sessile droplets coupled to optomechanical sensors

“…The buckled mirror also functions as a flexible membrane exhibiting relatively high- Q mechanical vibrational modes ( e.g. , Q ∼ 100 in air) in the MHz-frequency range, while also exhibiting extreme sensitivity to external static 18 and dynamic 19 pressure variations. Since this membrane mirror also forms one end of a high-finesse, spherical mirror optical resonator ( i.e.…”

“…They are formed by a controlled thin-film buckling process 17 which results in a partially evacuated region embedded between a lower planar Bragg mirror and an upper curved (i.e., buckled) mirror. The buckled mirror also functions as a flexible membrane exhibiting relatively high-Q mechanical vibrational modes (e.g., Q ∼ 100 in air) in the MHz-frequency range, while also exhibiting extreme sensitivity to external static 18 and dynamic 19 pressure variations. Since this membrane mirror also forms one end of a high-finesse, spherical mirror optical resonator (i.e., with Gaussian beam cavity modes), changes in its position are easily and sensitively read out by locking the wavelength of an interrogation laser near a resonant line of the cavity (i.e., the so-called 'tuned-to-slope' technique).…”

All-Optical, Air-Coupled Ultrasonic Detection of Low-Pressure Gas Leaks and Observation of Jet Tones in the MHz Range

“…We previously conducted several studies on the optical properties of these devices, including their suitability for quantum electrodynamics due to the high finesse (~10 3 –10 4 ) and small mode volumes (as low as ~1.5 λ 3 ) routinely obtained [ 17 , 18 , 19 ], their applications in microfluidics as open-access cavities for liquids [ 20 ], and their ability to be fabricated with large birefringence and polarization mode non-degeneracy [ 21 ]. More recently, we demonstrated that our devices function as extremely sensitive optomechanical sensors for both static pressure differentials [ 22 ] and ultrasonic signals in air and water [ 16 , 23 ]. Notably, the ultrasonic force sensitivity is one or more orders of magnitude lower than other air-coupled ultrasound sensors, with a bandwidth spanning several MHz [ 24 , 25 , 26 ].…”