| Summary: | Solid-state lasers are capable of providing versatile output characteristics with greater flexibility compared to other popular laser systems. Lasing action has been achieved in many hundreds of solid-state media, but Nd-ion doped gain media are widely used to reach high power levels with short pulses.
In this work, commercially available Nd:KGW crystal served as a gain medium to achieve pulsed operation at 1067 nm. This laser crystal offers large stimulated emission crosssection and gain bandwidth which facilitates generation of high peak power pulses in the picosecond regime. The KGW crystal is monoclinic and biaxial in structure, and anisotropic in its optical and thermal properties. Due to poor thermal conductivity, this crystal can be operated within a limited power range before crystal fracture takes place. To reduce the amount of heat deposited in the gain media, we introduced a new pumping wavelength of 910 nm which reduces the quantum defect by more than 45%.
Continuous-wave laser operation was optimized to operate in mode-locked regime. In order to achieve short light pulses from the continuous-wave laser, one of the end mirrors was replaced by a semiconductor saturable absorber mirror (SESAM) to generate 2.4 ps pulses at a repetition rate of 83.8 MHz. An average output power of 87 mW was obtained at lasing wavelength of 1067 nm and the beam was nearly diffraction limited with M^2 < 1.18. The peak power of the generated pulses was 427 W and energy of each pulse was >1 nJ. Pumping the crystal at longer wavelength (910 nm) reduced the thermal lensing of the crystal by half when compared to conventional pumping at shorter wavelength (808 nm). To the best of our knowledge, this is the first time passive mode-locking of a Nd:KGW laser was explored using the pump wavelength at 910 nm. === February 2017
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