Optimal Generation of Ten Individual Green-to-Red Raman Source for Wavelength-Dependent Real-Time OR-PAM Images

Quickly Alternating Green and Red Laser Source for Real-time Multispectral Photoacoustic Microscopy

“…The maximum Stokes order and maximum pulse energy were determined by the combination of the length of the Raman fiber and the peak power of the incident light obtained through experiments [ 22 ]. The 5 and 30 m Raman fibers, chosen here, obtain the maximum pulse energy at the wavelengths of 545 nm (1 st order Stokes peak) and 655 nm (8 th order Stokes peak), respectively [ 22 ]. The coupling efficiency of the Raman fiber was measured to be approximately 50 %.…”

“…When the pump light has sufficient power to induce SRS in the silica optical fiber, the pump light gets downshifted in frequency by 13.2 THz, depending on the Raman gain coefficient ( ) of silica. The Raman threshold power, , for the SRS effect to occur can be described by the following equation: [ 22 , 23 , 27 ] where is the Raman gain coefficient in the medium, is the effective fiber length, and is the effective core area. If of the Raman fiber is increased or is narrowed, for generating SRS can be lowered.…”

“…If the peak power of the pump light is strong, multiple-order Raman downshift will cause cascaded frequency shifts in a silica optical fiber with an interval of 13.2 THz. Recently, our research group reported the generation of multiple-wavelengths using SRS sources as one of the OR-PAM applications [ 22 ]. An increased number of SRS peaks up to the tenth Stokes order of 695 nm, with a pulse energy of up to 116 nJ, and a PRR of 300 kHz from a pump light of 532 nm was reported [ 22 ].…”

“…Recently, our research group reported the generation of multiple-wavelengths using SRS sources as one of the OR-PAM applications [ 22 ]. An increased number of SRS peaks up to the tenth Stokes order of 695 nm, with a pulse energy of up to 116 nJ, and a PRR of 300 kHz from a pump light of 532 nm was reported [ 22 ]. A 700 nm SRS laser, providing a pulse energy of up to 200 nJ and a PRR of 50 kHz, was used for photoacoustic imaging of Prussian blue nanoparticles in a mouse tumor [ 23 ].…”

“…Even though the SRS sources facilitated multispectral imaging, the real-time OR-PAM images at different excitation wavelengths, however, could not be obtained. It is difficult to manually adjust the optical power of the pump light to achieve the optimal condition for each Raman Stokes light of the desired excitation wavelength to acquire the wavelength-dependent photoacoustic images [ 22 ].…”