Laser Science and Technology Center (LASTEC), Delhi, is developing a space qualified diode pumped
Nd: YAG laser transmitter capable of generating 10 ns pulses of 30 mJ energy @ 10 pps. This paper presents the results of experiments for comparative studies between electro-optic and passively Q-switched Nd: YAG laser in a crossed porro prism based laser resonator. Experimental studies have been performed by developing an economical bench model of flash lamp pumped Nd: YAG laser (rod dimension, &nullset; 3 X 50 mm). Electro-optic (EO) and Passive Q-switching were performed employing LiNbO<sub>3</sub> crystal (9 x 9 x 25 mm) and Cr: YAG (7 &nullset; 10 mm) saturable absorber respectively. Laser output of 30 mJ was achieved in EO Q-switching mode by optimizing Pockels cell operation. More than 80 % Q-switching efficiency was achieved. However, at the same input level in passive Q-switching mode at optimized initial transmission of Cr: YAG, only 36% efficiency could be achieved. Comparative studies were made for output pulse energy at different input levels. In passive Q-switched mode, deviation from the optimum flash lamp input either stops the lasing action or leads to multiple pulsing. Thus in view of the very stringent requirements of reliability and efficiency of space-based system, the electro-optical method of Q-switching has been adopted in the design.
This paper discusses the development plan of multiwave Lidar at Laser Science and Technology Centre
(LASTEC) at Delhi. The Lidar is designed mainly for the detection of very low concentrations of Chemicals and
pollutant of the order of few ppm level at a remote distance of 5 kilometres. This Lidar system not only detects the
pollutant it also identifies and quantifies the pollutant. The Lidar is supported by live software and library to display the
required information online.
Computer simulations have been carried out to optimize the IR Differential Absorption Lidar (DIAL) system in order to measure the gaseous pollutants released by the industries. The concentration of the gaseous pollutants due to elevated sources is computed using the Gaussian dispersion model. For given atmospheric conditions and stack physical parameters, the downwind distance (x) at which the SO<sub>2</sub> reaches the safe limit of its toxicity has been computed at given other two coordinates (y, z) with respect to chimney. The gaseous pollutants released by the industries will be effectively monitored by the proposed DIAL system, which will be placed at New Delhi (28.35 degrees N, 77.12 degrees E), India. The performance of the Lidar has been optimized based on the various system parameters incorporating the atmospheric conditions and stack physical parameters. Further, the backscattered return powers at on- & -off line wavelengths, the required energy to be transmitted and the position at which the lidar system should be posted have been computed in order to monitor SO<sub>2</sub>.
The paper describes the theoretical and experimental investigation of high power Gas Dynamic Laser(GDL, λ~10.6μm) interaction studies with a pressurized hollow metal(MS) target. The design and development of such type of target which has been shown bursting as well as burning effect at the time of interaction have been carried out. It has been filled by gas mixture of H<sub>2</sub> and Air in the range of flammability limit. Various parameters like power density, target thickness, filling pressure, mixture ratio etc have been optimized. High mass flow GDL of power level about several KW in unstable mode provides power density about 3.2 KW/Cm<sup>2</sup> by a beam delivery system at distance 25m. Since target material is thin and heat diffuses through it rapidly, by maintaining the required power density, rupturing is accomplished by heating an area of the pressure vessel to a temperature at which it will fail under the pressure load. Rupture initiates a propagating crack which spreads the damage over a large fraction of the pressure vessel. The gas mixture ignites due to its contact with atmosphere and explodes with a massive sound level of the order of 130dB. The sound level was measured by a Decibel meter. Temperature distribution along radial and depth have been studied theoretically. Surface temperature during interaction has been measured. Experimental data has been validated with theory. These study shows a very attractive demonstration showing potentiality of scientific applications of High Power CO<sub>2</sub> Laser.