Introduction to different types of lasers

Laser technology is widely used in modern manufacturing, engraving, cutting, communication, and many other industries. From industrial machines to consumer laser engravers, different types of lasers are designed for different applications.

Although all lasers work based on the principle of stimulated emission, they use different laser materials, structures, and wavelengths. These differences determine their performance, cost, and suitable applications.

This article introduces the basic working principle of lasers and explains the four main types: solid lasers, gas lasers, semiconductor lasers, and fiber lasers.

What Is a Laser?

The word laser comes from the phrase "Light Amplification by Stimulated Emission of Radiation."

The concept of stimulated emission was first proposed by Albert Einstein in 1917. Later, researchers experimentally confirmed this principle, which eventually led to the development of modern laser technology.

A laser is an artificial light source that produces a highly concentrated beam of light. Because of its high intensity and accuracy, lasers are often described as:

• "The fastest knife"
• "The most accurate ruler"
• "The brightest light"

A laser device usually contains three key components:

1. Pump Source

The pump source provides energy to the laser system. It excites the atoms inside the laser medium.

2. Gain Medium

The gain medium, also called the working material, absorbs energy from the pump source and produces amplified light.

3. Resonant Cavity

The resonant cavity controls light reflection and amplification. It allows the laser to oscillate in a specific mode and produces the final laser beam.

What Is Laser Processing?

Laser processing uses a high-energy laser beam focused through an optical system to modify or process materials. By moving the laser beam and the workpiece relative to each other, lasers can perform operations such as: Cutting, engraving, etching, welding and precision micro-processing.

Laser processing is widely used because it offers several advantages:

• Works with many types of materials
• Causes little material deformation
• Provides high processing accuracy
• Requires low energy consumption
• Produces less pollution
• Supports long-distance and automated processing

Because of these benefits, laser processing has become an important manufacturing technology.

Main Types of Lasers

Different lasers use different working materials, structures, wavelengths, and excitation methods. Based on the laser medium, lasers are generally divided into four main categories:

Wavelengths of commercially available lasers

1. Semiconductor Laser

Semiconductor lasers, also known as laser diodes, are lasers that use semiconductor materials as their working material. Semiconductor lasers take electric injection semiconductor lasers as an example. GaN, GaAs, and other materials are usually added to the semiconductor material to make a semiconductor junction diode.

When a large enough current is injected into the diode, the electrons (negatively charged) in the middle active region will spontaneously recombine with holes (positively charged) and release the excess energy in the form of photons, which will then be amplified by multiple reflections in the resonant cavity to form a laser.

Basic structure of semiconductor laser

2. CO₂ Gas Laser

A CO₂ gas laser is a laser that uses CO₂ gas as the medium. In the tube filled with CO₂ gas, electrode plates are arranged to generate discharge. The electrode plate is connected to an external power source, allowing it to input high-frequency power as an excitation source.

Plasma is generated in the gas due to the discharge between the electrodes, and the CO₂ molecules are converted into an excited state. When the number increases, stimulated emission begins.

Structure of CO2 Laser

3. YAG Solid Laser

YAG laser solid laser is a solid laser that uses YAG crystal as the laser medium. YAG refers to the crystallization of yttrium aluminum garnet with the addition of neodymium. The laser is configured such that excitation LDs are arranged on both sides parallel to the axis of the YAG crystal. A pair of mirrors is used to form a resonator, and a Q-switch is placed between them. Used for marking, cutting, engraving, and welding metal.

Structure of YAG solid Laser

4. Fiber Laser

Fiber laser uses optical fiber as the medium and is the product of the development of interrupt amplification technology for long-distance communication into high-power output laser. Optical fibers consist of a core that transmits light in the center and a metal cladding that surrounds the core in concentric circles. Fiber laser uses this core as the laser medium to amplify light.

The fiber laser is generally composed of pulsed light called a seed light source (seed light) generated by a laser diode (Seed LD), and then amplified by more than two fiber amplifiers. The excitation LD is equipped with multiple single-tube emitters (one for the light-emitting layer). Each LD has a low power output, so it has the advantage of a small thermal load and achieves a long life.

In addition, the greater the number of LDs, the more high-power output laser can be achieved. Fiber laser oscillation efficiency is high, and compared with solid lasers and gas lasers, it has the characteristic of lower power consumption.

Structure of Fiber Laser

The optical fiber for amplification (preamplifier, main amplifier) has a three-layer structure, including a core and two metal cladding layers. The excitation light enters the inner metal cladding (inner cladding) and the Yb-added core, causing the atoms inside the core to transform into an excited state.

The laser is enclosed in the core and advances, and then amplified by exciting atoms. The further it advances in the medium, the stronger the intensity. Unlike solid-state or gas lasers, the light goes in one direction and does not go back and forth.

Optical fiber structure for amplification

Blue Laser: A New Choice for Consumer Laser Engraving

Blue lasers are a type of semiconductor laser. A common blue laser uses GaN (gallium nitride) as the working material and has a wavelength of around 450 nm. Blue light has a high absorption rate for many materials, including: wood, metal, ceramics, organic matter, etc.

With improvements in blue semiconductor laser production and power output, blue lasers have become increasingly popular in consumer laser engraving machines.

Compared with traditional CO₂ engraving machines, blue laser engravers can provide a more affordable option for home users and small businesses. For example:

• LONGER RAY5 5W Laser Engraver is an entry-level blue laser engraver designed for affordable engraving applications.
• LONGER Laser B1 40W is a higher-power model designed for deeper cutting performance.

Conclusion

Lasers are available in many different forms, and each type has its own advantages. Solid lasers, gas lasers, semiconductor lasers, and fiber lasers use different materials and structures, which affect their wavelength, efficiency, and applications.

For industrial manufacturing, fiber and solid-state lasers are widely used for precision processing. For consumer engraving, blue semiconductor lasers have become popular because of their compact design and lower cost.

Understanding the differences between laser types can help users choose the right laser technology for their specific needs.