Wavelength-switchable ns-pulsed active mode locking fiber laser for photoacoustic signal generation

Abstract

We present a novel design for a wavelength-switchable nanosecond-pulsed erbium-doped fiber laser that simultaneously achieves a repetition rate of the order of hundreds of kilohertz as well as pulse energies in the hundred-nanojoule range to fulfil the requirements of photoacoustic (PA) imaging applications. Instead of conventional Q-switching of a single-wavelength output, rapid switching among multi-wavelength outputs in the 1600 nm region can be performed by tuning acousto-optic modulation frequencies under low-order active mode-locking conditions. The pulse repetition rate of the laser can be tuned from 200 kHz to 1 MHz, depending on the mode-locking order. In order to verify the potential of our proposed design for use in real-time PA applications, we detected PA signals generated by an absorbing target using a PA signal detection system with our dual-wavelength laser outputs.