This monograph provides information on laser applications in (i) bioscience for painless refractive and general surgery; (ii) in industry, the importance of laser in marking, cladding, ultraviolet lithography, and diamond processing; and (iii) in defence, the underwater application and uranium enrichment with efficient infrared lasers and possible clean energy by controlled nuclear fusion. This monograph covers laser basics, laser beam propagation, and most important cost-effective laser applications in bioscience, industry, and defence. Its use in bioscience is described for painless refractive and general surgery, highly effective coagulation for internal and external bleeding, and detection and curing diseases. It also highlights future applications of laser in preventing infectious and virus diseases for which there is no effective medicine. In industry, besides cutting and welding, laser finds importance in marking, cladding, ultraviolet lithography, and diamond processing. The future applications in deep hole drilling with compact high power fibre and ceramic laser that will be economical for oil exploration are discussed. In defence, laser will find more use in underwater application and uranium enrichment with efficient infrared lasers and possible clean energy by controlled nuclear fusion. The concept of ultra high power laser development using upper atmosphere as amplifying medium to deflect/disintegrate large asteroid hit earth has been discussed.