Introduction

COIL is a chemical laser in which the required pumping energy for population inversion is released via a chemical reaction. This property makes the COIL attractive for defence application because it eliminates the need for electrical power supply at remote locations. Among other chemical lasers, COIL has the advantages of power scalability, short wavelength (1.315 μm) compatible with fiber (Grunewald et al.) for remote operation and also better laser material interaction.

In COIL, a gas−liquid phase reaction between basic hydrogen peroxide and chlorine gas at sub-atmospheric pressure (Azyazov et al.) produces the pumping source, singlet oxygen. This is diluted with sufficient nitrogen buffer gas to reduce the various loss mechanisms. Part of the pump energy contained in the singlet oxygen is used in the dissociation of iodine molecules into iodine atoms and the rest is used to excite these iodine atoms by near resonant energy transfer reaction. The interaction of singlet oxygen with atomic iodine at appropriate flow conditions results in the generation of laser gain medium inside the laser cavity from where the laser output power is extracted using an optical resonator.

To develop a high power COIL, it is important to study the gain characteristics, i.e., the small signal gain and the saturation intensity of the active medium under different flow conditions and to evaluate the optimum cavity coupling for achieving maximum output power. In this chapter, different COIL input parameters required for optimal gain medium formation in the laser cavity have been analyzed and gain characteristics using simplified saturation model (SSM) (Hager et al.) for the development of high power COIL have been estimated. The resonator parameters and output mirror coupling are evaluated keeping in view the resonator stability, diffraction loss, utilization of mode volume and laser beam divergence. On the basis of these parameters, the laser cavity and optical resonator for high power COIL have been developed and tested.

COIL gain medium formation

Introduction

A low intensity conflict is the most common form of warfare today and is likely to be so in foreseeable future. Data suggests thatmore than 75%of the armed conflicts sinceWorldWar II have been of low intensity variety. Low intensity conflict operation is a military term used to refer to the deployment and use of troops and/or assets in situations other than conventional war. As compared to a conventional war; in the case of low intensity conflict operations, armed forces engaged in the conflict operate at a greatly reduced tempo, perhaps with fewer soldiers, reduced range of tactical equipment and limited scope to operate in a military manner. Moreover, use of artillery is avoided in the case of conflicts in urban territories and use of air power is often restricted to surveillance and transportation of personnel and equipment. Low intensity conflicts pose an alarming threat to national security and is an area of concern for the whole of the international community today. Its scope extends from emergency preparedness and response to domestic intelligence activities to riot and mob control, from combating illegal drug trafficking to protection of critical infrastructure, fromhandling counter-insurgency and anti-terrorist operations to detection of nuclear and biological agents, from detection and identification of chemical, biological warfare and explosive agents to detection of concealed weapons. Laser and opto-electronics technologies play an important role in handling low intensity conflict situations. The key advantages of the use of laser technology in such applications are near zero collateral damage, speed of light delivery and potential for building non-lethal weapons. Some of the well established laser devices in low intensity conflict (LIC) applications include laser dazzlers for close combat operations, mob/riot control and protection of critical infrastructures from aerial threats; lidar sensors for detection of chemical, biological and explosive agents; Femto second lasers for imaging of concealed weapons; lasers for sniper and gun fire location identification and so on. Use of laser vibrometry and electron speckle interferometry techniques for detection of buriedmines and high power lasers for disposal of unexploded ordnances are emerging applications of laser technology for homeland security. This chapter briefly describes both established and emerging applications of laser and opto-electronics technologies in homeland security in terms of salient features, potential usage and international developments.