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The Types Of Lasers By Different Classifications

by Winnie Li Posted on December 06, 2023

In just a few decades, laser technology has become a pivotal element of modern innovation. Compact laser printers, industrial laser cutting machines, and surgical laser tools – these are just a few examples of how lasers have integrated into various facets of our daily lives.

But do all applications share the same type of laser? Of course, not! Although the core principle is the same, their wavelength, generation medium, and use case differ.

This article offers a clear overview of these differences. It uncovers the basic working principle, different classifications of lasers, and the purpose each laser type serves.

In This Article

  • What Is a Laser?
  • Laser Types by The Gain Medium
  • Laser Types by Mode of Operation
  • Laser Types By Wavelength
  • What Is The Most Commonly Used Type Of Laser?
  • How To Choose The Types Of Laser For Your Needs?
  • Laser Types FAQs
  • Conclusion

What Is a Laser?

A laser is a coherent, monochromatic, and unidirectional beam of light. It can be intense and powerful enough to cut through surfaces. The word ‘LASER’ itself defines the working principle. It’s acronym for ‘Light Amplification by Stimulated Emission of Radiation.’

The laser concept was first introduced by Albert Einstein in 1916. He found that electrons, when stimulated by light (energy), reach higher energy levels on excitation and then release energy excess energy as light, which we call laser.

principle of laser

The core component of a laser is a gain medium (liquid, gas, or solid) whose electrons get excited by energy and a light amplification process occurs. The gain medium gets energy from pumping, usually an external flashlight or another light source, powered by electricity.

When the atoms in the gain medium absorb energy from the pumping source, they reach an excited state. These excited atoms then release particles of light called photons. These photons are all of the same wavelength, which gives the laser light its unique color (if it’s in the visible spectrum).

Inside the laser, two mirrors are facing each other on either end of the gain medium. One mirror is a high reflector, meaning it reflects almost all the light that hits it. The other is an output coupler, which is partially transparent. 

The photons released by the excited atoms bounce back and forth between the two mirrors. Each time they pass through the gain medium, they stimulate more excited atoms to release more photons. This process amplifies the light. Eventually, the light becomes intense enough to pass through the output coupler as a concentrated beam of light, what we call a laser beam.

Laser Types by The Gain Medium

The most common way to classify laser is based on the optical gain medium. Primarily, the gain medium can be either of the three physical states i.e. solid, liquid, or gas. Among these three main types, three popular lasers: diode, fiber, and CO2 lasers are quite well-known. So, they have been explained separately.

Solid-State Lasers

These lasers use a solid material as the gain medium, typically a glass or crystalline material doped with ions of rare earth metals. The doping material absorbs pumping energy and emits light.

Ruby laser, a type of solid-state laser, was the first laser ever made. Another well-known name is the Neodymium-doped Yttrium Aluminum Garnet (Nd: YAG) laser. This laser is quite powerful and used for welding and cutting purposes.

Some pulsed solid-state lasers are used in the medical field for cancer removal, kidney stones, and hair removal surgeries.

Gas Lasers

Gas lasers, as their name suggests, use gases as the gain medium. The electric current is passed through a gas mixture, which excites the gas atoms and causes them to emit photons. The gases typically used are noble gases (helium, neon, argon, krypton), nitrogen, and CO2.

Helium-Neon (HeNe) lasers are low-cost and used in optical research and educational purposes. Other than that, we see gas lasers in material processing, cutting, welding, and laser surgeries.

Liquid Lasers

Dye lasers use a liquid dye solution as the gain medium. The dye molecules are excited by a light source, which leads to the emission of photons. Rhodamine is a commonly used dye in these lasers.

Due to their tunability and the ability to generate different wavelengths, dye lasers are especially useful in spectroscopy, medical diagnostics, and laser medicine. They are also used in atmospheric pollution monitoring and research.

Semiconductor Lasers

Technically, semiconductors are also an example of solid-state lasers. They employ a semiconductor diode (like gallium arsenide) as the gain medium. When an electric current is passed through the PN junction of this diode, electrons and holes (electron vacancies) recombine, releasing energy in the form of photons. This process is known as electroluminescence.

Commonly, semiconductors are all diode lasers. However, there are a few exceptions, for instance, pumped semi-conductor lasers (where another laser optically pumps light) and quantum cascade lasers are non-diode semi-conductor lasers.

Due to their small size and efficiency, semiconductor lasers are widely used in consumer electronics, laser pointers, CDs, DVDs, desktop laser machines, barcode scanners, and various other sensing applications.

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Fiber Laser

Fiber lasers use a fiber optic cable as the gain medium. The core of the fiber (silica) is doped with rare-earth elements like erbium, ytterbium, or neodymium. The fiber is then “pumped” with light from diode lasers or other light sources, which excites the doped atoms. As these atoms release photons, the light is amplified within the fiber.

Fiber lasers are quite powerful and highly valued in industrial applications for cutting, welding, and marking. They are also used in medical applications, telecommunications, and for research purposes.

CO2 Laser

CO2 laser primarily uses carbon dioxide gas as the gain medium, mixed with other gases like nitrogen and helium. The laser operates by electrically stimulating the CO2 mixture.

They are slightly less powerful than fiber lasers, however still capable of cutting through a range of materials. In industrial settings, they are used for cutting, welding, and engraving various materials, including plastics, wood, and metals. In the medical field, they are used for skin resurfacing treatments, dermatology, and multiple other surgical procedures.

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Laser Types by Mode of Operation

The next classification is based on the mode of operation i.e. how does the laser beam radiate out? There are primarily two modes of operation.

Continuous-Wave Lasers

Continuous-wave (CW) lasers emit a constant, unbroken beam of light as long as they are powered. There is no interruption or modulation in the light output.

CW lasers are commonly used in applications where a consistent and steady source of light is required. For instance, in industrial cutting or welding applications, we need a constant energy supply to vaporize or melt materials.

Pulsed Lasers

Pulsed lasers emit light in short bursts or pulses. This mode is used when continuous operation is not practical, or when high peak power is required. In this case, the continuous output of a traditional laser is altered with different methods like Q-switching, pulse pumping, and mode-locking.

Use Cases by Pulse Duration:

The pulse duration can range from milliseconds to femtoseconds. This duration is helpful in different scenarios.

  • Milliseconds: Lasers with millisecond pulses are often used in medical treatments, such as dermatological procedures for tattoo removal and hair removal.
  • Microseconds: Microsecond pulsed lasers find applications in industrial processing, like precision drilling and micro-machining, where heat impact needs to be minimized.
  • Nanoseconds: Used in scientific research and in some medical applications, nanosecond pulses allow for high-precision work without significant heat damage to surrounding areas.
  • Picoseconds and Femtoseconds: Ultra-short pulsed lasers like picosecond and femtosecond lasers are used in highly precise surgical procedures, for instance, eye surgeries, and in scientific research where extremely high precision and minimal thermal impact are required.

An important point to note: A laser machine's optical power (labeled on it) is its average laser power. In continuous wave lasers, the average power and peak power of the laser are almost the same. For instance, if it's 40W laser, that means its peak power will be 40W. But for a pulsed laser machine, in which laser generation is in short bursts, the average power is quite less than its peak power. A 40W pulse laser may have 4000W peak power.

Laser Types By Wavelength

The lasers can also be classified based on the wavelength of light it emits. We categorize it based on where it falls on the electromagnetic spectrum.

laser wavelength spectrum

©ResearchGate

Ultraviolet Lasers

Ultraviolet (UV) lasers typically operate in the wavelength range of about 100 to 400 nanometers. Common UV lasers include the Excimer laser (like the Argon Fluoride laser at 193 nm) and the Nitrogen laser (at 337 nm). These lasers are known for their ability to produce short-wavelength, high-energy light.

UV lasers are widely used in photolithography for semiconductor manufacturing, in dermatology for skin treatments, in LASIK (eye surgeries), and in laser engraving for high-precision work.

Visible Lasers

Visible lasers operate within the range of about 400 to 700 nanometers. Their wavelength lies in the visible spectrum i.e. these are colored lasers which humans can see.

Examples include the Argon-ion laser (blue-green light, around 488 nm and 514.5 nm), the Helium-Neon laser (HeNe, red light at 632.8 nm), and multiple other dye lasers which cover a wide range of colors in the visible spectrum.

Visible lasers are used in a variety of applications such as in spectroscopy, holography, biomedical applications, laser pointers, and in entertainment for laser shows.

Infrared Lasers

This is a broader spectrum that covers most of the laser types and it has been segregated into three sub-sections.

Near-Infrared: These lasers operate in the range of about 700 nm to 1,400 nm. Common examples are Nd:YAG lasers (at 1064 nm) and Diode lasers.

Mid-Infrared: Wavelengths range from 1,400 nm to 3,000 nm. Lasers like the Erbium-doped YAG laser (Er: YAG) at 2940 nm fall into this category.

Far-Infrared: These extend from 3,000 nm to 1 mm. CO2 lasers (at 10,600 nm) are the most notable in this range.

Infrared lasers have a wide range of applications, including in fiber-optic communications (near-infrared), medical surgeries like laser skin resurfacing (mid-infrared), and industrial cutting and welding (far-infrared).

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What Is The Most Commonly Used Type Of Laser?

It’s hard to list one type. Typically, three names: fiber lasers, CO2 lasers, and diode lasers are quite popular among manufacturers and hobbyists:

Fiber Lasers

Fiber lasers are among the most powerful lasers used in cutting applications at the industrial level. They are capable of cutting metals and a variety of other materials due to their high power and precision. They are mostly used for industrial scale due to expensive pricing and heavy-duty equipment.

CO2 Lasers

CO2 lasers are slightly less powerful compared to fiber lasers but are still very effective for a wide range of cutting applications. They can cut through materials like wood, plastic, paper, and leather. Industrial as well as desktop CO2 machines are available.

Diode Lasers

Diode lasers are used for low-powered, DIY cutting needs and are commonly found in at-home desktop laser cutters. They are suitable for cutting thinner or softer materials. They are popular among hobbyists and small businesses due to their compact size and affordable price.

How To Choose The Types Of Laser For Your Needs?

From the sea of options, it’s hard to tell which laser will suit you. To identify the laser that best fits your needs, consider these key factors:

Application

First, identify how you will be using the laser. The application will largely dictate the type of laser you need. If it’s for industrial use, such as cutting or welding, you might require a high-power fiber laser. For DIY projects, a less powerful diode laser will be sufficient. In medical facilities, specific lasers like Nd: YAG or Excimer are used for treatments and surgeries.

Power Requirements

Lasers come in different optical powers. The strength of the laser you need depends on the material and the nature of the task. If you need something for cutting thick materials or metals, a laser with higher power (>50W) is necessary. For engraving or light cutting at home, a lower-power laser (10 - 50W) might be adequate.

Budget Considerations

Consider your budget as the price of laser cutting machines varies significantly based on their power type and capabilities. Small, at-home lasers can cost a few hundred dollars, suitable for DIY engraving and cutting. Industrial lasers, offer more precision and power and can reach up to hundreds of thousands of dollars. The surgical setup prices are comparable with industrial machines.

Machine Consideration

The budget may land you the type of machine. However, be aware that the laser machine can be compact or heavy-duty. For at-home DIY needs, a small desktop laser machine would be more than enough. While for industries, you may need to get them customized for your needs.

Safety Consideration

Lasers are also divided into different laser safety classes, with each class defining a certain level of safety. For environments where safety is a major concern, such as in schools or homes, Class 1 laser products are recommended as they are considered the safest. In industrial or controlled environments, higher-class lasers can be used with appropriate safety measures.

Laser Types FAQs

What Types Of Laser Are Usually Used In Laser Cutting?

Cutting requires a high-powered and continuous laser beam. At the industrial level, fiber lasers are recommended for metallic and other material cutting. For DIY or at-home cutting needs, CO2 and diode lasers work perfectly.

What Types Of Laser Are Usually Used In Laser Engraving?

The laser machines that can cut through materials are also capable of engraving it. CO2 lasers are generally recommended for engraving non-metals. Besides fiber lasers, few infrared lasers are quite effective for laser engraving metals.

Conclusion

Laser technology is a dynamic and constantly evolving field, with the potential for new types and advancements emerging in the future. Given the complexity and variety of lasers available, classifying them is necessary to understand their characteristics and applications.

In this article, we have explored common classifications and the popular types of lasers within each category. Among these, fiber, CO2, and diode lasers are particularly noteworthy for their widespread use and versatility.

If you're considering a desktop laser cutter or engraver, especially the CO2 or diode types, we recommend exploring the xTool laser machine collection. Our range offers smart, compact solutions tailored for small businesses and hobbyists.

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