Figure 7
From: Air-coupled ultrasound detection using capillary-based optical ring resonators
(a) Schematic of the chamber to immerse the ring resonator (colored in red) into D2O. The optical taper was placed on top of the ring resonator. The air-gap between the Cr film and the D2O chamber was ~1.4 mm. The distance between the top surface of D2O and the ring resonator was 2.0 mm. (b) Air-coupled PA signal detected by the ring resonator (a = 65 μm, t = 7.5 μm), immersed in D2O. The data were averaged 64 times. The PA peak around 27 μs was the signal from the PA pulse. The dampened “ringing” response can be seen after the initial peak signal. (c) Frequency response of the ring resonator towards PA pulse. A broadened peak at 840 kHz with a FWHM of 200 kHz can be obtained with D2O encapsulation.
