The principle of laser generation
The principle of laser generation
LASER is written as "Light Amplification by Stimulated Emission of Radiation", which means that by the principle of "excitation emission", the amplification of light waves is generated, which is called "laser". The motion state of electrons can be divided into different energy levels. When electrons transition from high energy level to low energy level, they will release electromagnetic waves of corresponding energy (the so-called spontaneous radiation). In a normal light-emitting body, the electrons release photons randomly, and the photons do not have the same properties, such as the light from a tungsten lamp.
When the applied energy is injected into an energy level system by means of electric field, photon, chemistry, etc., electrons will jump from the low energy level to the high energy level. When the photons generated by spontaneous radiation encounter the electrons that jump to the high energy level due to the applied energy, the electrons of the high energy level will be induced to move to the lower energy level and release photons (the so-called excited radiation).
All the optical properties of stimulated radiation and the original spontaneous radiation include: The frequency, phase, direction of advance, etc., are the same. When these excited photons encounter other electrons that have been pushed up the energy level by the applied energy, they produce more of the same photons. Finally, the intensity of the light becomes larger and larger (that is, the energy of the light is amplified), and unlike ordinary light, all the photons have the same frequency, phase, and direction of advance.
To amplify light, you have to create an environment where high-energy electrons outnumber low-energy electrons, so that there's a chance that high-energy electrons will bump into photons and release new ones, rather than randomly. The generation of laser requires three elements, namely the Pumping Source, the GainMedium and the Optical Cavity/Resonator.
Pumping Source: Pumping Source
Energy is supplied to electrons of lower energy order and excited into electrons of higher energy order, such as charge discharge, photon chemistry and so on. . One common source of excitation is Xenon Flash Lamp, but other wavelengths of laser can also be used as excitation source.
The "Gain Medium" :
The physical properties of the material in which the electrons are excited and emitted affect properties such as the wavelength of the laser light produced.
Optical Cavity/Resonator:
It's two mirrors parallel to each other, one full reflection, one half reflection. The purpose is to make the excited light pass through the gain medium many times to get enough amplification, when the amplification can penetrate the semi-mirror, the laser is emitted from the semi-mirror. Therefore, this semi-reflective mirror is also called an Output Coupler. The distance between the two mirrors also has a selective effect on the laser wavelength output, only the distance between the two mirrors can produce resonance wavelength can generate laser.
