How a laser works: from medium pumping to the optical resonator
- The laser beam is formed in the active medium, which has been previously energized.
- The optical resonator amplifies light, creating a powerful beam.
- Early lasers used optical pumping, now they use electric current.
- Lasers are used in medicine, industry, and communications.
The laser (Light Amplification by Stimulated Emission of Radiation) has become one of the key technologies of the modern world. Its light is characterized by high monochromaticity, directionality, and coherence, making it indispensable in various fields—from surgery to microchip production lines.
Principle of operation: from energy to light.
To generate a laser beam, it is necessary to create conditions under which the atoms or molecules of the active medium are in a so-called inverted state. This is achieved by 'pumping' the medium with external energy: first, energy is introduced into it, and then the occurring process stimulates the emission of photons that are in phase, frequency, and direction.
The light obtained is repeatedly reflected between two mirrors of the resonator, amplifying with each pass. This system allows for the collection of energy from individual photons into a powerful, narrowly directed beam.
The evolution of pumping methods
The first experimental lasers, created in the mid-20th century, used optical pumping — external light radiation, often from a lamp, excited the active medium. This method required bulky equipment and limited the compactness of the device.
With the development of technology, electric current is increasingly used as a power source. Electric discharge allows for a significant reduction in the size of the laser, simplifying its integration into portable devices and industrial lines.
There is now a wide range of lasers, differing in the type of active medium (solid-state, gas, semiconductor) and the method of pumping. Nevertheless, the basic principle — energy → inversion → amplification in the resonator — remains unchanged.
The practical significance of lasers is hard to overestimate. In medicine, they are used for precise surgical cuts, photocoagulation, and skin therapy. In industry, lasers are used for cutting metal, welding, marking, and measurements. Furthermore, they form the basis of optical communication, allowing for the transmission of vast amounts of data over fiber optics.
Thus, the modern laser is the result of a combination of fundamental physical principles and engineering solutions aimed at increasing efficiency and reducing the size of the device.
Source: N+1
