Lasers can be classified in many ways, the most famous of which are solid, gas, liquid dyes, semiconductor and fiber lasers. Solid-state laser media are similar to Ruby rods. Flash tubes wound around them pump energetic atoms. In order to work effectively, solids must be doped, which is a process of replacing some atoms with impurity ions, so that they have appropriate energy levels to produce a laser with a certain precise frequency. Solid-state lasers produce high-power beams, usually very short pulses. In contrast, gas lasers use inert gases (so-called excimer lasers) or compounds of carbon dioxide (CO2) as media to produce continuous light. CO2 laser has powerful function and high efficiency. It is often used in industrial cutting and welding. The liquid dye laser uses the solution of organic dye molecule as medium. The main advantage is that it can be used to generate wider optical bands than solid-state and gas lasers, and even can be "tuned" to produce different frequencies.
According to the wavelength, the coverage ranges from far-infrared, infrared, visible, ultraviolet to far-ultraviolet. There are various raycus fiber laser source
, such as X-ray laser and y-ray laser.
According to different excitation modes, there are light excitation (light source or ultraviolet light excitation), gas discharge excitation, chemical reaction excitation, nuclear reaction excitation, etc.
According to different output modes, there are continuous, monopulse, continuous and ultrashort pulses.
From the point of view of power output, the continuous output power is small to microwatt level, and the maximum can reach megawatt level. The output energy of the pulse can be from micro-joule to over 100,000 joules. The pulse width ranges from milliseconds to picoseconds or even femtoseconds (1 trillionth of a trillion).
All kinds of lasers meet different application requirements. For example, laser processing and some military lasers require high power laser or high energy laser (so-called intense laser). It is hoped that the pulse time will be shortened as far as possible in order to study some special fast processes. Some also put forward high requirements for improving the monochromaticity of light, improving the mode of output light, improving the intensity distribution of spot and requiring adjustable wavelength. These requirements urge laser researchers to explore continuously, so that the depth of exploration and the breadth of application of lasers have a great development.