Industrial lasers are broadly categorized into 4 types. The laser medium or construction used, the oscillation wavelength, and the excitation source are different. The laser medium is a substance that contains atoms that can convert the energy of the excitation light into laser light, and the types of lasers are categorized precisely according to the medium.
1. Solid-state laser: generally YAG laser and YVO4 laser, laser medium using YAG, YVO4 crystallization.
2. Gas laser: widely used CO2 gas as the medium of CO2 laser.
3. Semiconductor laser: with an active layer (light-emitting layer) structure of the semiconductor as the medium of the laser.
4. Fiber laser: into the 21st century after the widespread popularity of a laser, as described in the word, to the optical fiber as a medium.
Solid-state laser (YAG laser, side pumping method)
Side pumping method YAG laser is a solid-state laser that uses YAG crystals as the laser medium. YAG refers to the crystallization of Yttrium Aluminum Garnet with the addition of neodymium. The laser consists of an excitation LD on both sides parallel to the axis of the YAG crystal, a pair of mirrors to form a resonator, and a Q-switch between the two. It is used for marking, cutting, engraving, and welding of metals.
Solid-state laser (YVO4 laser, side pumping method)
The side pumping method YVO4 laser is a solid-state laser that uses YVO4 crystals as the laser medium. YVO4 refers to yttrium vanadate crystals that have neodymium added to them as well as YAG. A pair of mirrors is used to form a wiper by unilateral irradiation of excitation light from the end face of the YVO4 crystal, and the mirrors are configured with a crystal and a Q-switch between them. High-quality laser light can be output.
Gas laser (CO2 laser)
CO2 laser is a laser that uses CO2 gas as a medium. Inside the tube filled with CO2 gas, an electrode plate is configured to generate a discharge. The electrode plate is connected to an external power supply so that it can be fed with high frequency electricity as an excitation source. A plasma is generated in the gas due to the discharge between the electrodes, and the CO2 molecules are transformed into an excited state, which increases in number and begins to radiate with excitation.
Semiconductor laser
Semiconductor crystals of different materials are overlapped to form an active layer (light-emitting layer) to generate light. The light is amplified by allowing it to travel back and forth between a pair of mirrors forming the two ends, ultimately producing a laser.
Fiber laser
Fiber lasers use optical fibers as the medium and are a product of the development of interruptive amplification technology for long-distance communication into high-power output lasers. The fiber consists of a core that transmits light in the center and a metal cladding that covers the core in concentric circles. Fiber laser amplifies light with this core as the laser medium.
Fiber laser is generally composed of pulsed light called seed light generated by a laser diode (Seed LD), which is then amplified by more than two fiber amplifiers. The LD for excitation is equipped with a number of single tube emitter (one for the light-emitting layer) LDs, and each LD has a low power output, so it has the advantage of a low thermal load and realizes a long life. In addition, the higher the number of LDs, the higher the power output of the laser can be realized. Fiber lasers have high oscillation efficiency and lower power consumption than solid-state lasers and gas lasers.
The optical fiber for amplification (preamplifier, main amplifier) is a 3-layer construction including a core and 2 layers of metal cladding. Excitation light enters the inner metal cladding (inner cladding) and the Yb-added core, causing the atoms inside the core to shift to an excited state. The laser light is enclosed within the core advancing and then amplified by the excited atoms, becoming more intense the further it advances within the medium. Unlike solid-state or gas lasers, the light travels in one direction and does not travel back and forth.
