Novel implementation of KLTN-based modulator in Tm:YLF pulsed laser

Laser systems emitting in the 2&mu;m region have many applications in a variety of fields, such as gas spectroscopy, medical surgery, material processing, LIDAR, and as a pumping source for the mid-IR region lasers. Many applications require high energy pulsed sources due to the short exposure which result in mitigated thermal damage. A common way to implement Q-switched lasers is by using an electro-optic (EO) modulators. In general this spectral range is lack with variety of active modulators.<br/> The KLTN crystal is a promising candidate for EO modulation at long wavelengths up to 5.5&mu;m. KLTN at the paraelectric phase manifests a quadratic EO effect which upon approaching the ferroelectric phase transition, becomes remarkably large, exhibiting an electrically induced change in the refractive index of approximately 0.01 while maintaining high optical quality. In our previous work, an actively Q switched laser at the 2&mu;m range implementing the polarization modulation method with KLTN crystal was demonstrated, this method was restricted to anisotropic gain crystals. Here we present a new configuration of actively Q-switched laser based on a quadratic electro-optical KLTN deflector that can be applied also in isotropic crystals as well. The deflection was achieved due to the electro-optical effect gradient along the vertical axis, which was caused by inducing an electric field gradient along the vertical axis due to the trapezoid shape. The deflection method was implemented in a Tm:YLF laser (1880nm), Maximal high energies/pulse of 4.2- 6.9mJ were achieved in three repetition rates of 0.4, 0.5 and 0.7kHz with a relativity low applying voltage of 500V and with 15ns pulse duration range.