Widely tunable visible pulsed cascaded Raman fiber laser source

Abstract

We have generated a visible laser by second harmonic generation from a pulsed Cascaded Raman fiber Lasers (CRFL) continuously tunable in 1060nm-1600nm, using type-I LBO. To eliminate the requirement of precise synchronization and control, we employed a passive Q-switching mechanism for the Yb laser pumping the Raman module. The pump is made continuously tunable in Yb-band with wavelength dependent feedback in the Qswitched cavity ensuring continuous wavelength tunability of generated Raman Stokes. We utilized a large modearea amplifier to amply pulse-energy without introducing temporal instability and optimized Raman module for efficient pump conversion. We demonstrated a widely tunable visible laser with ∼ µJ pulse-energy and ∼ 20 − 65kHz repetition-rate, 40-200ns pulse duration. This is the first demonstration of a high pulse energy nanosecond laser continuously tunable in 530nm-600nm making it a versatile laser source for numerous biomedical applications. The wavelength tunable range can be extended to 700nm by utilizing type-II LBO.