Laser Principle

The “Laser” word  means “light amplification by stimulated emission of radiation”.

A laser is a device that emits light in the form of extremely narrow wavelengths of specified wavelength. This device consists of a light collector or activator that is located inside the light intensifier chamber. This material strengthens the light beam produced by an external energy source (electricity or light).

For the first time, Einstein gave the original laser plan (Maser). The laser’s work is that, by irradiating a photon into a particle (an atom or molecule or ion), another photon is released, both of which are both frequencies. With the continuation of this process, the number of photons increases, which can create a slice of photons.

The laser, in terms of its nature, is no different from ordinary light, and the physical properties of the laser differentiate it from the light created from other sources. From the earliest days of laser technology, its special properties have been recognized, which has created these greatly adapted properties for the vast applications of this phenomenon in various sciences, especially industry and medicine. Advancement of knowledge without laser technology is not possible.

Perhaps the most important part of atomic physics is the discussion of laser physics. By energizing the electrons of an atom, they can be transmitted to higher circuits. But this new home is not so stable for electrons, and electrons prefer to return to their original circuit by giving energy back. This energy is released as a specific frequency photon. That is, an energy unit. The light of these photons is made. So if we do this simultaneously with a large number of atoms, we can create a single-frequency optical beam. In addition, with phase methods and precision, one-phase beams can be produced. This phenomenon is the basis of the production of laser beams. Its unique laser features distinguish it from other light sources that are not found in any other light source. The laser has four features:

  1. Coincidence
  2. Monochrome
  3. Low divergence
  4. Parallel Beam 


The proposed use of stimulated of radiation from a system with an inverse population to strengthen microwave waves independently was given by Weber, Jordon, Ziegler, Basu, Tanz and Prokhoru. The first practical use of such amplifiers was conducted by the Jourdon, Ziegler, and Towns groups at the University of California. This group chose the name maser, called “Microwave Amplification by Stimulated Emission of Radiation”.

Theoretical foundations of laser theory were put forward by Albert Einstein in 1916, but it took quite a few years to allow industry and technology to build the first laser. In 1953, Charles Towns invented the microwave waveform amplifier and wanted to continue experimenting with the replacement of visible light rather than infrared, and at the same time it was considered by many laboratories throughout the world as a serious competition. The first laser was first proposed in 1958 by Microwave Transition in ammonia molecules manufactured by Teltobetb for the first time to propose laser activity in optical frequencies in an article by Scowloy and Townes. The term laser was proposed at the same time in an article by Gordon Hold, Ph.D. student at Columbia University, and Theodore H. Maiman developed a pulsed ruby ​​laser in 1960. The first gas laser was also made by Ali Young, a physicist in 1961, using helium and neon. In 1962, the proposed semiconductor lasers were introduced. Laser light is also called ray coil.

Since 1966, the semiconductor laser has been focused on optical communications in Japan and the United States, and has been cognizant of the potential for direct translation to very high frequencies

Evolution and growth
With the ever-increasing advances in quantum mechanics and particle sizes of light and the production of high-powered mirrors, scientists developed higher-power laser (high power lasers) and coherence lasers.

The invention of lasers dates back to 1958 with the publication of scientific papers on infrared and optical radiation. The publication of these articles has led to an increase in scientific research by scientists around the world. In the communications sector, experts also confirmed the ability of the laser to replace the transmission or transmission of electrical power. But how to transmit pulses can cause a lot of problems. In 1960, scientists transmitted light pulses, then used lasers. The laser produced a lot of light that was more than a million light brighter than sunlight. The laser beam can be very much affected by atmospheric conditions such as rainfall, fog, low clouds, and things in air testing such as birds.

Scientists have also proposed novel designs to support light from encountering obstacles. Before the laser can send signals to the phone. Another important invention is the fiber optic waveguide used by telecommunications companies to send audio, information and image. Today, electronic communications are based on photons. The wavelength division multiplexing technology or various light-colored colors are used to send trillion bits of fiber optic.


Laser elements

The laser instrument is an optical oscillator that emits a very parallel beam of coherent radiation and is made up of three parts:

External energy source 
Amplifier environment
Optical cavity or resonator
The pumping
The pumping is an external energy source that generates an inverse population in a laser environment. The amplification of the light wave or photon radiation field occurs only in a laser environment in which there is a reversal of the population between two energy levels. For the laser to work, it is necessary that the number N2 atoms in the energy level E2 of the number of atoms N1 is larger in energy level E1. This is called the inverse of the population. Population inversion and induction are working together in the laser environment, and they enhance the light. Otherwise, the light wave passing through the laser environment will be weakened.

Blowers can be optically, electrically, chemically or heat-generating, provided that they provide the necessary energy that can be coupled with the laser environment to stimulate the atoms and create an inverse population.

In gas lasers like He-Ne, the most commonly used pump is electric discharge. The important factors governing this kind of pump are the electron stimulating sections and the life span of different energy levels. In some gas lasers, the liberated electrons produced in the discharge process directly collide with and excite atoms, ions, or laser molecules. In other lasers, it is caused by collisions between atomic atoms or molecules-molecules.

Nd: YAG lasers use optic pumping

Laser environment
The amplifier environment or laser environment is an important part of the laser instrument, which is a light emitting source and can be gas, liquid or solid, and determines the wavelength of the laser beam. Many lasers are referred to as the type of laser environment they use, for example helium-neon (He-Ne), carbon dioxide and neodymium: aluminum garnet (Nd: YAG)

Laser output
The output of the lasers is two-way pulse and continuous. The pulse is in fact a light that spins in a short time. This pulse width today is less than femtosecond.

Laser applications

Physics and Chemistry
Biology and Medicine: laser knife, laser drill, physiotherapy and …
Military industry: laser tracker, laser gun, laser guided bomb and …
Industry: laser markers (engraving), laser welding, laser cutting, diamond cutting, laser scroll, construction industry
Nuclear fusion
Optical communication
Construction of Transistor and Integrated Circuit
Lithography and Sterilotography
Optical data processing and recording
Material processing
Allograft (holographic)
Measurement (speedometer)
Laboratory and research: measurement, synthesis of materials and …
coating with laser method

After laser carbon dioxide was invented in 1964, the use of laser was enhanced by its high precision and minor errors in medical fields, and it was possible for surgeons to use photons instead of surgical knives. Lasers can now enter the body and perform surgeries.

Video and audio discs and compact discs A video disc is a video recorder that can be displayed on a regular TV device. Video creators record data using a saboteur, which is read by laser. A common method of recording involves cutting slits with different lengths and distances. The depth of these slices is 1/4 laser wavelength, which is used in the reading process. At the time of reading, the laser beam focuses on a single groove. When the groove occurs in the path of the laser beam, the reflection decreases due to the devastating interference between the reflected light of the groove walls and it decreases. Doing a photo with a groove makes a strong reflection. In this way, television information can be digitally recorded.

In January 2013, physicists made particles of a potassium-based quantum gas. When exposed to laser and magnetic fields, it gets to negative temperatures. In this thermodynamic temperature, the material begins to exhibit unknown properties