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What is the Structure of the Laser Source?

Jan 29, 2021

1. Laser working medium

 

   Laser generation must choose a suitable working medium, which can be gas, liquid, solid or semiconductor. There are nearly a thousand kinds of working media, and the laser wavelengths that can be generated include ultraviolet to far infrared. There are four main types of working materials commonly used at present: cylindrical (most used at present), flat, disc and tubular.

 

2. Incentive source

 

   In order to cause the population inversion in the working medium, a certain method must be used to excite the atomic system to increase the number of particles in the upper energy level. Generally, gas discharge can be used to excite the medium atoms with kinetic energy, which is called electrical excitation; pulsed light sources can also be used to illuminate the working medium, which is called optical excitation; there are thermal excitation, chemical excitation, etc. Various excitation methods are visually called pumping.

 

3. Condenser system

 

        The condensing cavity has two functions, one is to effectively couple the pump source and the working material; the other is to determine the distribution of the pump light density on the laser material, thereby affecting the uniformity, divergence and optical distortion of the output beam . The working substance and the pump source are installed in the condenser cavity, so the quality of the condenser cavity directly affects the efficiency and working performance of the pump. The elliptical cylindrical condenser cavity is currently the most commonly used small solid-state laser.

 

4. Optical cavity

 

   It is composed of a total reflection mirror and a partial reflection mirror, and is an important part of a solid-state laser. The optical resonant cavity not only provides positive optical feedback to maintain the laser continuously oscillating to form stimulated emission, but also restricts the direction and frequency of the oscillating beam to ensure high monochromaticity and high directivity of the output laser. The simplest and commonly used optical resonant cavity of a solid-state laser is composed of two plane mirrors (or spherical mirrors) placed opposite each other.

 

5. Cooling and filtering system

 

  The cooling and filtering system is an indispensable auxiliary device for the laser. The solid-state laser will produce a serious thermal effect when it is working, so cooling measures are usually taken. It mainly cools the laser working material, pumping system and concentrating cavity. Cooling methods include liquid cooling, gas cooling and conduction cooling, but the most widely used method is liquid cooling.

       To obtain a laser beam with high monochromaticity, the filter system plays a big role. The filter system can filter most of the pump light and some other interference light, making the output laser monochromaticity very good.