Optical readout of acoustic responses of an external-cavity diode laser

Due to external cavity, the external-cavity diode laser (ECDL) is sensitive to the harsh environment. It can serve as a very convenient tool for measuring or comparing acoustic responses and analysis of acoustic insulation characteristics of materials and mechanical structure. Focused on the ECDL, improvement of the laser acoustic responses and suppression of the laser system drift are critical. But the acoustically-induced vibration coupled with complex disturbance will contribute to the frequency fluctuation, therefore it is difficult to investigate the dynamic response characteristics of laser frequency to acoustic signals separately. In order to decouple the acoustic response from environmental noise and to reduce system drift, a frequency stabilization system by virtue of grating feedback and current feedback is demonstrated with the a wide-bandwidth loop. After recording the system response, the amplitude-frequency characters are achieved through fast Fourier transform (FFT). After analyzing the correlation of the laser frequency fluctuation and the acoustic stimulant signal’s frequency, the acoustic dynamic response characteristics of the ECDL is depicted experimentally. By contrasting the acoustic response characteristics of the ECDL with or without the acoustic proofing case, the acoustic insulating effect could be mapped directly. The experimental results show that the acoustic proofing case can not be remained valid for all frequency bands effectively. It can also act as the experimental criteria for optimizing the design of laser mechanical structures and acoustic insulation systems. Furthermore, this optical system could be employed as a detector extending to acoustic sensing or acoustic precise measurement.