Suppression of Brillouin oscillation in transparent free-standing diamond thin films in picosecond ultrasound

Abstract

Brillouin oscillation appears in picosecond ultrasonics for a transparent specimen because of backward light scattering by moving strain pulse. Its amplitude is comparable with those of other responses, such as pulse-echo signals and through-thickness resonance, obscuring these non-Brillouin-oscillation responses. We here find that Brillouin oscillation can be suppressed in a transparent free-standing film by coating both sides with a metallic thin film of appropriate thickness and that this peculiar behavior is caused by strain pulses generated on both sides with a slight phase difference. This phenomenon allowed us to fabricate a Brillouin-oscillation-free diamond free-standing film, which showed a high capability for sensor applications.

High sensitivity biosensing scheme based on a GHz phononic crystal waveguide

“…Indeed, resonant sensors based on picosecond ultrasonics have been proposed, showing the potential for ultra-sensitive detection. [19][20][21] However, ultrashort-pulsed lasers inevitably bring excess heat, so the development of picosecond-ultrasonic biosensors based on biomolecule attachment are hindered by temperature-induced denaturing, 22) precluding effective detection. The common use of metallic materials with high thermal conductivity (such as Pt, Au) for ultrasonic generation and biomolecule attachment exacerbates this problem.…”