Depending on the nature of the active media, lasers are classified into three main categories, solid, liquid, and gas. · Solid Laser(Diode): is an optically clear material composed of a crystal and an impurity dopant. The output wavelength is determined for the most part by the impurity. Examples: Ruby laser. · Gas Laser : are very much like fluorescent light sources. An electric current pass through the optical cavity exciting atoms, resulting in the emission of light. Examples: CO2. · Liquid Laser: liquids are more homogeneous as compared to solids and have larger density of active atoms as compared to the gasses. [27] Main Component of Laser: · Lasing Medium. · Pump Source. · ...