A laser diode is a semiconductor device similar to a light emitting diode (LED). Use the p-n junction to emit coherent light in which all waves are on the same frequency and phase. This coherent light is produced by the laser diode using a process called “Amplification of light by stimulated emission of radiation”, which is abbreviated as LASER. And since a p-n junction is used to produce laser light, this device is called a laser diode. Before learning more about the work process of a laser diode.
Sunlight or most artificial light sources contain waves of multiple wavelengths and are offset together. Light waves from monochromatic light sources such as the incandescent bulb are also not in phase with each other. Unlike previous light sources, laser diodes produce a narrow beam of laser light in which all light waves have similar wavelengths and travel together with their aligned peaks. This is the reason why the laser beams are very bright and can focus on a very small point.
How does a laser diode work?
The operation of a laser diode is carried out in three main steps:
The laser diode consists of a p-n junction where holes and electrons exist. (Here, a hole means the absence of an electron). When a certain voltage is applied to the p-n junction, electrons absorb energy and make the transition to a higher energy level. The holes are formed in the original position of the excited electron. The electrons remain in this state of excitation without recombining with holes for a very small period of time, called “recombination time.” The recombination time is approximately one nanosecond for most laser diodes.
After the life of the upper state of the excited electrons, they recombine with the holes. As electrons fall from the highest energy level to a lower energy level, the energy difference becomes photons or electromagnetic radiation. This same process is used to produce LED light. The energy of the emitted photon is given by the difference between the two energy levels.
We need more coherent photons of the laser diode than those emitted through the spontaneous emission process. A partially reflective mirror is used on each side of the diode so that the photons released from the spontaneous emission are trapped in the p-n junction until their concentration reaches a threshold value. These trapped photons stimulate the excited electrons to recombine with holes even before their recombination time. This results in the release of more photons that are in exact phase with the initial photons and thus the output is amplified. Once the photon concentration exceeds a threshold, they escape from partially reflective mirrors, resulting in a coherent bright monochromatic light.
What is its application in aesthetic medicine?
One of the applications of the diode laser is in aesthetic medicine. The diode laser is mainly characterized by having a longer wavelength than the other options available in the market so that this laser penetrates somewhat more into the skin, so it is especially suitable for darker skin or thicker hair and deep It can also work well for lighter skin, but as long as the hair is thick or medium.
What are the advantages of using a diode laser?
• Having a longer wavelength, it penetrates the skin better, so it is especially recommended for people with dark skin and thick hair.
• This longer wavelength provides deeper and safer penetration into the skin.
• People with brown or black hair are the most benefited by this type of laser.
• It is especially suitable for large body areas, which allows a safe and painless treatment.