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The Different Characteristics And Applications Of Various Types Of Lasers

Mar 03, 2020

Laser technology has came into people's life from all aspects, but there are many types of lasers, with different wavelengths and different characteristics, so the fields of application are different. I believe that most people have a little headache in the face of complicated laser types. Therefore, this article summarizes the various types of lasers and explains the characteristics and practical applications of each type of laser one by one.

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According to different working media, lasers are divided into solid lasers, gas lasers, dye lasers, semiconductor lasers, fiber lasers and free electron lasers. Among them, there are many subdivided types of solid-state lasers and gas lasers. Except for free electron lasers, the basic working principles of all kinds of lasers are the same, including the pump source, optical resonator and gain medium.

In solid-state lasers, light is generally used as a pump source, and crystals or glasses capable of generating laser light are called laser working substances. The laser working substance is composed of a matrix and an activating ion. The matrix material provides a suitable existence and working environment for the activating ion, and the laser generating process is completed by the activating ion. Commonly used activating ions are mainly transition metal ions, such as chromium, diamond, nickel, and rare earth metal ions, such as neodymium ions. A reflector coated with a dielectric film on the surface serves as a resonant cavity lens, one of which is a full-mirror and one is a half-mirror. When different activating ions, different matrix materials and different wavelengths of light are used for excitation, a variety of different wavelengths of laser light will be emitted. Various types of solid-state lasers and their applications.

Ruby laser

The output laser wavelength is 694.3nm, and the photoelectric conversion rate is low, only 0.1%. However, its long fluorescence life is conducive to energy storage, and it can output high peak pulse power. The laser generated by a ruby rod with the thickness of a pen core and long fingers can easily penetrate the iron sheet. Before the emergence of more efficient YAG lasers, ruby lasers were widely used in laser cutting and drilling. In addition, 694nm light is easily absorbed by melanin, so the ruby laser is also used for the treatment of pigmented lesions (skin spots on the skin).

Titanium sapphire laser

Due to its crystal properties, it has a wide tunable range (that is, a wavelength range), and can output light with a wavelength of 660nm-1200nm according to needs. Coupled with the maturity of frequency doubling technology (which can double the frequency of light, that is, halving the wavelength), the wavelength range can be extended to 330nm-600nm. Titanium sapphire lasers are used in femtosecond spectrometry, non-linear optics research, white light generation, terahertz waves generation, etc., and have applications in medical beauty.

YAG

It is the abbreviation of yttrium aluminum garnet. This substance is currently the most excellent laser crystal matrix with comprehensive characteristics. It can output 1064nm light after doped with neodymium (Nd), and the maximum continuous output power can reach 1000w. In the early days, an inert gas flash was used as the pump source of the laser. However, the flash pump method has a wide spectral range, poor coincidence with the absorption spectrum of the laser gain medium, and a large thermal load, which results in a low photoelectric conversion rate. Therefore, using LD (laser diode) pumps can achieve high efficiency, high power, and long life of the laser. Nd: YAG laser can be used in the treatment of hemangiomas to inhibit tumor growth. However, the thermal damage of this laser to tissues is non-selective. While coagulating tumor blood vessels, excess energy will also damage surrounding normal tissues, leaving scars after surgery. Therefore, Nd: YAG lasers are mostly used in surgery, gynecology, facial features, and less in dermatology.

Yb: YAG, doped with Yb (Yb) in YAG, can output 1030nm light. Yb: YAG's pump wavelength is 941nm, which is very close to the output wavelength, which can achieve a pump quantum efficiency of 91.4%, and the heat generated with the pump is suppressed to within 10% (most of the input energy is converted into output A small part of the laser energy becomes heat, which means that the conversion efficiency is very high), which is 25% to 30% of Nd: YAG. Yb: YAG has become one of the most noticeable solid-state laser media. LD-pumped high-power Yb: YAG solid-state lasers have become a new research hotspot and are regarded as a major direction for the development of high-efficiency, high-power solid-state lasers.

In addition to the above two types, YAG can also be mixed with erbium (Ho), erbium (Er), and the like. Ho: YAG can generate 2097nm and 2091nm lasers that are safe for human eyes. It is mainly suitable for optical communication, radar and medical applications. Er: YAG outputs 2.9 μm light. The human body has a high absorption rate at this wavelength, and has great application potential for laser surgery and vascular surgery.

Dye laser

A laser that uses an organic dye as the laser medium, usually a liquid solution. Compared to gaseous and solid-state laser media, dye lasers can often be used over a wider range of wavelengths. The wide bandwidth makes them particularly suitable for tunable and pulsed lasers. However, due to its short medium life and limited output power, it has been basically replaced by a solid-state laser with a tunable wavelength such as titanium sapphire.

Semiconductor laser

It is a laser using semiconductor material as the working substance. There are three types of excitation methods: electric injection, electron beam excitation and optical pumping. Small size, low price, high efficiency, long service life, low power consumption, can be used in the fields of electronic information, laser printing, laser pointer, optical communication, laser TV, small laser projector, electronic information, integrated optics The most important type of laser.

Fiber-optic laser

It refers to the laser using rare earth element-doped glass fiber as the gain medium, which has a wide range of applications, including laser fiber communication, laser space remote communication, industrial shipbuilding, automobile manufacturing, laser engraving, laser marking, laser cutting, printing rolls, metal Metal drilling / cutting / welding (brazing, quenching, cladding and deep welding), military defense security, medical equipment and equipment, large-scale infrastructure, as a pump source for other lasers, etc.

Free electron laser

It is a new type of high-power coherent radiation source that is different from traditional lasers. It does not require gas, liquid or solid as working material, but directly converts the kinetic energy of high-energy electron beams into coherent radiant energy. Therefore, the working substance of a free electron laser can also be considered as a free electron. It has a series of excellent characteristics such as high power, high efficiency, wide-range tuning of wavelengths, and the time structure of ultra-short pulses. Apart from it, no laser can have these characteristics at the same time. It has very promising prospects in physics research, laser weapons, laser fusion, photochemistry, and optical communications.


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