1.7 μm Flexible Nanosecond Pulse Generation

The third near-infrared (NIR-III) optical window (1600–1870 nm) is located at carbon-hydrogen (C-H) stretch resonance overtone, indicating that organic substances being rich in C-H bonds have strong absorption in this band [1]. These spectroscopic features offer a new optical window for overtone-absorption-based photoacoustic imaging (PAI) [2]. In addition, customized excitation laser with multiple wavelengths enables multi-contrast photoacoustic imaging of mixture component samples based on photoacoustic spectra [3]. In this context, we introduce a flexible <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$1.7\mu \mathrm{m}$</tex> nanosecond pulsed laser based on a semiconductor optical amplifier (SOA) with continuously adjustable central wavelength (1700 nm to 1750 nm), repetition rate (1 kHz to 10 MHz), and pulse duration (5 ns to 100 ns), offering promising potential for hyperspectral PAI.