High-Frequency Ultrasonic Hydrophone Based on a Cladding-Etched DBR Fiber Laser

Distributed-Bragg-reflector (DBR) fiber-laser-based ultrasonic hydrophone has been found to possess increased detectable frequency range due to the improved sensitivity in the high-frequency region when the fiber cladding thickness was reduced. A wet etching technique is utilized to reduce the fiber diameter of the DBR laser. The peak response frequency moves from 21 to 40 MHz when the fiber diameter was reduced from 125 to 68 m.