Continuous lasers operate based on the principle of continuous wave (CW) emission of laser light. Here's how they generally work:
Gain Medium:
Continuous lasers have a gain medium, which is a material capable of amplifying light through stimulated emission. This gain medium could be a gas, liquid, or solid, depending on the type of laser.
Excitation:
The gain medium is excited using an external energy source. This excitation could be achieved through various methods such as electrical discharge, optical pumping, or chemical reactions, depending on the type of laser.
Population Inversion:
The excitation process creates a population inversion in the gain medium. This means that there are more atoms or molecules in an excited state than in the ground state.
Stimulated Emission:
When a photon passes through the gain medium, it stimulates the excited atoms or molecules to undergo a transition to a lower energy state, emitting another photon of the same wavelength and phase. This process is called stimulated emission and is the basis of laser amplification.
Optical Cavity:
The gain medium is placed within an optical cavity, which consists of two mirrors placed facing each other. One of these mirrors is fully reflective, while the other is partially transparent to allow some light to pass through.
Feedback and Amplification:
The emitted photons bounce back and forth between the mirrors of the optical cavity. As they pass through the gain medium, they stimulate further emission, resulting in the amplification of the light.
Continuous Wave Emission:
As long as the excitation source continues to provide energy to maintain the population inversion in the gain medium, and the losses in the optical cavity are compensated, the laser will emit a continuous beam of coherent light.
Output Coupling:
Some of the amplified light is allowed to exit the optical cavity through the partially transparent mirror, forming the output beam of the laser.
Continuous lasers are used in various applications where a continuous, stable output beam is required, such as laser cutting, laser welding, laser engraving, and scientific research. The specific characteristics and performance of a continuous laser depend on factors like the type of gain medium, the excitation method, the optical cavity design, and the control mechanisms implemented in the laser system.
