Actively Q-Switched Multisegmented Nd:YAG Laser Pumped at 885 nm for Remote Sensing

An end-pumped actively Q-switched Nd:YAG laser using a multisegmented crystal rod as laser active material, directly pumped to the upper laser level by an 885-nm emitting diode is demonstrated. The Nd:YAG crystal was pumped both in CW and quasi-CW mode. The maximum energy per pulse obtained was 2.57 mJ at 1 kHz, with an overall efficiency of \(\sim 7.5\) %. The pulse duration was 22-ns full-width at half-maximum while the spatial beam profile was excellent ( \(M^{2}\!<\!1.3\) ).

I. Introduction

For many scientific and commercial applications such as laser remote sensing (LIDAR), free-space telecommunications, there is the necessity to use lasers operating in pulsed mode exhibiting high peak power, short pulse duration, high repetition rate and excellent Gaussian profile [1]. Diode end-pumped lasers employing Nd:YAG rods as active materials are considered to be very reliable solutions meeting all the above requirements [2], [3]. Longitudinal pumping has proven to be one of the most efficient methods as it is possible to match the mode of the pump beam to that of a resonant mode in the laser cavity, whereas restriction of the number of modes is feasible by focusing the pump radiation to a spot that is slightly smaller than the fundamental mode of the laser beam. However, there are certain daunting challenges associated with this pumping scheme [4].