**1. Introduction**

The growing product development for advanced applications such as aerospace, automobiles, electronics and medical devices requires materials with high strengthto-weight ratio. Advanced materials with superior properties are being developed by researchers around the world for meeting the growing demand. The materials such as nickel, titanium and their alloys, ceramics are known not only for high strength-to-weight ratio but also for higher level of corrosion resistance, prolonging capacity at higher temperatures with superior mechanical strength comparing to other engineering materials [1]. These materials have greater properties such as higher density and melting point, ductile, higher hardness and strength, hence conventionally machining these materials is very challenging. Despite, it can be machined using conventional techniques, but higher cutting forces and rigorous tool wear attributes to huge cost in shaping these materials to the requirement. Hence there were many unconventional machining processes (UMPs) developed to replace conventional machining processes. One of the UMPs is laser beam machining (LBM) which is extensively used machining those difficult-to-machine materials. LBM is considered suitable for machining hard materials LBM is characterized

by independency to hardness property of work material. LBM is gaining attention among the researchers and industry people because of its advantages such as higher light intensity with low power requirement, good focusing property within short duration of pulse, uniform heat distribution, eco-friendly nature which results in accuracy in machining, narrow heat affected zone, increased productivity and reduced manufacturing cost [2]. The upcoming sections describes in detail about the principle of laser and its types, mechanism of laser machining, advantages, applications and limitations of using LBM.
