What is laser
Laser is considered one of the four great inventions of the 20th century. Unlike natural light, laser light is a human-made invention based on quantum theory.
What sets laser light apart from natural light is its unique characteristics and the process by which it is generated. Laser is often referred to as “the fastest knife, the brightest light, and the most accurate ruler.”
Compared to natural light, laser light is highly intense, highly monochromatic, highly coherent, and highly directional.
Laser light is the result of atomic stimulated radiation. When the atoms are excited by the energy from the pump source, they can transition to a high-energy state. If they encounter an external photon with a specific frequency, they will release an identical photon. This process causes more atoms to transition and produce the same photon, resulting in stimulated radiation and the production of laser light.
The frequency, phase, direction of propagation, and polarization state of the photons produced by stimulated radiation and external photons are exactly the same, which is why laser light has the unique characteristics of high intensity, high monochromaticity, high coherence, and high directionality.
Schematic diagram of atomic energy level transition
Schematic diagram of the stimulated radiation process
Features of laser
- Good directivity
- Good monochromaticity
- High strength
- High coherence
History of laser
The commercial use of laser technology began in the 1970s and has since been rapidly developing. In 1917, Einstein first proposed the concept of stimulated radiation. The world’s first ruby solid-state laser was introduced in 1960.
During the 1970s, laser technology entered the commercial era and has continued to grow and expand since then. After studying the interaction between laser beams and matter, the application of laser technology has broadened and expanded, particularly in the industrial sector. In the 1990s, industrial applications of laser technology entered a stage of high-speed development.
Development history of laser technology
Two applications of laser
The high intensity, good monochromaticity, good coherence, and good directivity of laser light determine its two main application scenarios: energy laser and information laser.
Laser technology is known for its high energy density, making it ideal for various applications such as material processing, weapons, medical treatment, and others.
Laser’s good monochromaticity and directivity make it suitable for information transmission (optical communication) and distance measurement (optical measurement). Optical communication has several advantages over traditional electric communication, such as its high capacity, long-distance transmission capabilities, enhanced confidentiality, and lightweight nature.
Laser processing equipment
Laser processing is a prime example of precision processing technology, with its growth largely driven by the replacement of traditional processing methods.
Compared to other processing methods, laser processing offers several advantages, including high efficiency, high precision, low energy consumption, minimal material deformation, and ease of control.
These advantages can be attributed to two key characteristics of laser processing: non-contact machining and high energy density.
In laser processing, the heat generated by the interaction between the laser and the material completes the processing, with no physical contact between the processing tool and the material. This eliminates the effects of force on the processed material and results in relatively low residual stress. Additionally, the small diameter of the laser beam allows for high precision.
High energy density:
The power density of laser processing can reach over 107W/cm^2, which is thousands or even tens of thousands of times higher than other processing methods such as flame and arc. This higher power density allows the laser to process a small area on the material without affecting the surrounding area, leading to higher processing accuracy and efficiency.
- High efficiency
- Low energy consumption
- Small deformation
- Easy to control
Laser: the core unit of laser equipment
The laser is a crucial component in generating laser light and is the core component of laser equipment.
The value of the laser typically accounts for 20-40% of the total value of a complete set of laser processing equipment, and in some cases, it can be even higher.
The laser is where the processes of pumping and stimulated radiation take place. A typical laser consists of several parts, including the laser working material (which emits energy), the pump source (which provides energy), and the optical resonator (which facilitates the propagation of energy).
Basic structure diagram of laser
Types of laser
There are several methods for classifying lasers, but four of them are the most widely used:
Lasers can be classified based on the type of working substance they use, including gas lasers, solid lasers, liquid (dye) lasers, semiconductor lasers, excimer lasers, and others.
Gas lasers use gas as their working material. Examples of common gas lasers include CO2 lasers, He-Ne lasers, argon-ion lasers, He-Cd lasers, copper vapor lasers, and various excimer lasers. CO2 lasers are particularly widely used in industry.
In solid-state lasers, metal ions that are capable of producing stimulated emission are doped into a crystal and used as the working material. Commonly used crystals include ruby, corundum, aluminum garnet (commonly known as YAG), calcium tungstate, calcium fluoride, yttrium aluminate, and lanthanum beryllate. Currently, YAG is the most widely used crystal in solid-state lasers.
In liquid lasers, the working substance is a solution formed by dissolving organic dyes in liquids such as ethanol, methanol, or water.
Semiconductor lasers, also known as laser diodes, use semiconductor materials as their working materials, such as gallium arsenide (GaAs), cadmium sulfide (CDS), indium phosphide (INP), and zinc sulfide (ZnS).
A fiber laser uses glass fiber doped with rare earth elements as its working material. Fiber lasers are lasers that use fiber as the medium for the generation of laser light.
Fiber laser is known as the “3rd generation laser” due to its exceptional performance:
(1) The small volume, flexibility, low volume-to-area ratio, and high photoelectric conversion rate of the fiber result in a fiber laser that is miniaturized, intensified, and highly efficient in terms of heat dissipation and photoelectric conversion.
(2) The laser output from a fiber laser can be directly obtained from the fiber, making the fiber laser highly adaptable to processing applications in any space.
(3) The fiber laser’s structure, which lacks optical lenses in the resonant cavity, provides advantages such as ease of use, low maintenance, and high stability.
(4) The beam quality of a fiber laser is also exceptional.
|Types of laser||Typical type||Laser wavelength||Maximum output power||Energy conversion efficiency||Features|
|Gas laser||CO2 laser||About 10.6um infrared||1-20kw||8%～10%||Good monochromaticity and high energy conversion efficiency|
|Liquid laser||6G dye laser||UV to IR||–||5%～20%||The output wavelength is continuously adjustable, the energy conversion power is high, easy to prepare and cheap|
|Solid state lasers||YAG / ruby laser||Visible to near infrared||0.5-5kw||0.5%～1%||Low output power, low energy conversion rate and good monochromaticity.|
|Semiconductor lasers||GaAs diode laser||100nm―1.65um||0.5-20kw, two-dimensional array can reach 350kW||20% – 40%, laboratory 70%||High energy conversion power, small volume, light weight, simple structure, long service life and poor monochromaticity.|
|Fiber laser||Pulsed / CW fiber laser||1.46um―1.65um||0.5-20kw||30%-40%||Miniaturization, intensification, high conversion efficiency, high energy output, high beam quality, no optical collimation and less maintenance.|
Energy output waveform (working mode):
Lasers can be categorized into three types: continuous laser, pulsed laser, and quasi-continuous laser.
Pulsed lasers can be further classified based on the pulse width: millisecond laser, microsecond laser, nanosecond laser, picosecond laser, femtosecond laser, and attosecond laser.
This type of laser outputs a stable energy waveform continuously while in use, with high power. It is suitable for processing materials with large volume and high melting points, such as metal plates.
Pulsed lasers can be further divided into millisecond lasers, microsecond lasers, nanosecond lasers, picosecond lasers, femtosecond lasers, and attosecond lasers, depending on the pulse width. Femtosecond and attosecond lasers are commonly referred to as ultrafast lasers.
While the power of pulsed lasers is lower compared to continuous lasers, the machining accuracy is higher. As a general rule, the narrower the pulse width, the higher the machining accuracy.
This type of laser is between a continuous laser and a pulsed laser, where high-energy laser can be repeatedly outputted within a certain period.
|Classification method||Laser category||Features|
|Classification by working mode||CW laser||The excitation of the working material and the corresponding laser output can be carried out continuously in a long time range|
|Pulsed laser||It refers to a laser with a single laser pulse width of less than 0.25 seconds and working only once at a certain interval. It has a large output peak power and is suitable for laser marking, cutting and ranging.|
|Classification by pulse width||Millisecond (MS) laser||10-3S|
|Microsecond (US) laser||10-6S|
|Nanosecond (NS) laser||10-9S|
|Picosecond (PS) laser||10-12S|
|Femtosecond (FS) laser||10-15S|
Output wavelength (color):
Lasers can be categorized into several types based on their wavelength: X-ray lasers, ultraviolet lasers, infrared lasers, visible lasers, etc.
Lasers can be divided into three categories based on their power output: low-power lasers (<100W), medium-power lasers (100W to 1500W), and high-power lasers (>1500W).
Classification of lasers
Some of the major laser suppliers in the market include Coherent, IPG Photonics, n-Light, Newport Corporation, TRUMPF, Rofin (now a subsidiary of Coherent), DILAS, SPI Lasers (now owned by TRUMPF), Mitsubishi Electric, Kawasaki Heavy Industries, MAX Photonics, JPT Optoelectronics, Raycus Fiber Lasers, Fei Bo Laser, Guoke Laser, Anpin Laser, and HFB Laser.
You can also refer to the top laser cutting machine manufacturers for reference.