Q-switched mode locking with acousto-optic modulator in a diode-pumped Nd:YVO4 laser

Jan Jabczynski,Waldemar Zendzian,Jacek Kwiatkowski

doi:10.1364/oe.14.002184

Abstract

The Q-Switched Mode Locking (QML) regime provides the generation of relatively high peak power picosecond pulses train with energies of a few muJ each in a simple resonator. The fully modulated efficient QML regime was demonstrated in the diode-pumped Nd:YVO4 laser. The acousto-optic cell playing a double role of Q-switch and Mode Locker was located near flat output coupler. The two folding mirrors were mounted on the translation stages for matching the resonance frequency of the cavity to the radio frequency of acousto-optic modulator. The QML pulses with envelope durations of 100-150 ns and near 100% modulation depth were observed for wide range of pump powers and repetition rates. Up to 3 W of output average power, 100 muJ of the envelope energy, having approximately 5-8 mode-locked pulses were achieved.

Highlights

The ps pulses of μJ energies with dozens kHz pulse repetition frequency (PRF) are demanded in several areas, e.g., micro machining, ophthalmology, dental surgery etc
The Q-Switched Mode Locking (QML) regime provides the generation of relatively high peak power picosecond pulses train with energies of a few μJ each in a simple resonator
The fully modulated efficient QML regime was demonstrated in the diode pumped Nd:YVO4 laser

Summary

Introduction

The ps pulses of μJ energies with dozens kHz pulse repetition frequency (PRF) are demanded in several areas, e.g., micro machining, ophthalmology, dental surgery etc. Their high intensities together with relatively low heat deposition ensure precise removal of material during the short interaction time. Combination of different mode locking techniques (e.g. nonlinear mirrors [9], specially designed semiconductor saturable absorber elements [10], acousto-optic modulators [11]) with active Q-switches can lead to 100% modulation depth and stabilization of temporal and energetic parameters of QML regime. Conclusions were drawn and prospects for future work are given

Principle of operation of AO-QML laser

Investigation of QML generation

Conclusions