Broadband Hyperspectral SRS Microscopy with Fiber and Solid-State Sources for Bioimaging and Semiconductor Inspection

Stimulated Raman scattering (SRS) microscopy is a powerful imaging technique with diverse applications, such as visualization of molecular distributions [1] and characterization of crystalline material properties [2]. For enhancing the chemical contrast by broadband hyperspectral imaging, it is required to widely tune the frequency difference between the synchronized picosecond pump and Stokes pulses. Conventional tuning methods, such as spectral focusing of chirped pulses or wavelength tuning of a fiber laser, typically offer a limited spectral coverage of 300 cm <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$-1$</tex>. To overcome this limitation, fiber optical parametric oscillators (FOPOs) have emerged as alternative widely tunable light sources [3], [4]. A FOPO employing the dispersion tuning technique yields wide and fast wavelength tuning, whereas that using a delay stage enables synchronization with an external laser for low-noise detection and independent adjustment of the pump and Stokes wavelengths. However, the latter FOPO suffers from a slow tuning speed, hampering hyperspectral SRS imaging.