Basics of laser generation

The word "LASER" is an acronym for: Light Amplification by Stimulated Emission of Radiation.
L - Light : Light
A - Amplification: Amplification
S - Stimulation : Stimulation
E - Emission : Emission
R - Radiation : Radiation

They are classified according to different criteria:
- Type of reinforcement;
- The wavelength is in the infrared, visible or ultraviolet region of the spectrum;
- The operating mode is continuous or pulsed;
- The wavelength is fixed or adjustable.

The laser consists of the following elements:
Laser medium – the material in which the laser is generated.
medium can be: solid, liquid or gas.
Pump source – provides the necessary activation energy
laser environment that allows the laser to be generated.
Laser Resonator – Controls how the laser is generated
laser environment, consists of a rear 100% reflector and a
front partial reflector.

Generating a laser beam is a three-step process in which individual steps occur almost instantaneously.
1) Spontaneous emission – The pump source emits energy to the medium and excites the atoms of the laser medium so that the electrons in the atoms are temporarily transferred to a higher energy state. Electrons in this state cannot remain there indefinitely and fall back to a lower energy level. During this process, the electron loses the excess energy it gained by pumping energy by emitting a photon. The photons produced by this process, known as spontaneous emission, are the core of laser generation.

2) Stimulated emission – photons emitted by spontaneous emission eventually collide with other electrons in higher energy states. This happens in a very short time due to the speed of light and the density of excited atoms. The incoming photon "pushes" the electron from the excited state to a lower energy level and generates another photon.
These two photons are coherent, i.e. they are in phase, have the same wavelength and travel in the same direction. This process is called stimulated emission.

3) Amplification – photons are emitted in all directions. However, some travel through the laser environment, hit
resonator mirrors and is reflected back through the medium. The resonator mirrors determine the desired direction of amplification of the stimulated emission. For amplification to occur, there must be a higher percentage of atoms in the excited state than in the lower energy levels. This "population inversion" of several atoms in the excited state creates the necessary conditions for laser generation.

Laser types:
- (CO2) laser
Wavelength: 10.6 μm; far infrared ray
Laser medium: CO2-N2-He mixed gas (gas)
Average power [CW]: 50 kW (peak) (normal): 1-15 kW

- Lamp pumping (YAG) laser
Wavelength: 1.06 μm; near infrared ray
Laser medium: Nd3+:Y3Al5O12 garnet (solid)
Average Power [CW]: 10 kW (Cascade Type and Fiber Coupling Max) (Typical): 50 W - 7 kW (Efficiency: 1 - 4%)

- Laser Diode (LD)
Wavelength: 0.8-1.1 μm; near infrared radiation
Laser media: InGaAsP etc. (solid)
Average power [CW]: 10 kW -15 kW
Advantages: compact and high efficiency (20-60). %)

- Laser diode LD pumped solid state laser
Wavelength: about 1 μm; near infrared ray
Laser medium: Nd3+:Y3Al5O12 garnet (solid)
Average power [CW]: 13.5 kW (max fiber coupling) [PW]: 6 kW (max plate type)

- Disc laser
Wavelength: 1.03 μm; near infrared ray
Laser medium: Yb3+:YAG or YVO4 (solid)
Average power [CW]: 16 kW (cascade type max) Advantages: Fiber delivery, high brightness, high efficiency (15-25%)

- Fiber laser
Wavelength: 1.08 μm; near infrared ray
Laser medium: Yb3+:SiO2 (solid)
Average power [CW]: 100 kW (max fiber connection)

Laser beam delivery:
All lasers from 532 nm to 1080 nm deliver the laser to the welding zone using a flexible optical fiber.
cable. The convenience of fiber delivery greatly facilitates the integration of the laser into the finished laser
welding systems. Typically, the length of the delivery fiber is between 5 and 15 meters (m), although this can be
up to 50 m depending on the type of laser used. It provides flexible laser positioning,
which can be particularly useful for certain production lines.