Glossary

Light with a wavelength shorter than 200 nm. Difficult to propagate outside of a vacuum.

ArF (193 nm) and F2 (157 nm) excimer lasers fall under the category of vacuum ultra-violet light.

A correcting lens that condenses a laser beam onto a planar surface to ensure a constant scanning speed anywhere in the marking field.

[Equation for an f-theta lens]

Lenses designed so that the relationship between the image height (h) and the entry angle (θ) equals [h=fθ]. This enables constant laser scanning speeds on the surface of a target.

Laser systems that arc and discharge high voltage through a gas mixture sealed inside of a tube, changing the gas to plasma.

CO₂ (carbon dioxide) and He-Ne (helium-neon) are commonly used. CO₂ lasers are used for marking and processing, while helium-neon lasers are used as light sources in opto-electronics.

Solid-state

Nd:YAG

YAG (Yttrium Aluminum Garnet)

Fundamental wavelength (1064 nm)

• Universal marking applications

Second-harmonic (532 nm) (Green laser)

• Used for fine marking and processing, silicon wafers, plastics and reflective metals etc

Third-harmonic (355 nm) (UV laser)

• Used for micro-processing, LCD repair and also plastic and reflective metal marking

Nd: YVO₄ (1064 nm)

YVO₄ (Yttrium Vanadate)

• Used in applications needing high peak power and extremely stable beam power

LD: (650 to 905 nm)

• Semiconductor lasers (GaAs, GaAIAs, GaInAs)

Gas

CO₂ (10.6 μm)

• Used for marking labels, etching plastics/resins, processing and cutting applications.

He-Ne (630 nm) (red) is common

• Most commonly found in measurement devices.

Excimer (193 nm)

• Uses a combination of inert gas and hydrogen gas to create a shorter UV wavelength.
  Most commonly used for optometry to vaporize the lens of human eyes.

Argon (488 to 514 nm)

• Used primarily in scientific applications and biomedical related research.

Liquid

Dye (330 to 1300 nm)

• Used more widely in scientific applications.
  Dye are energized by laser light to produce florescent light.

The optimal laser will differ depending on the desired processing application.

A pulse that possesses high-energy amplified via Q-switch.

A phenomenon where excess energy accumulation in the laser medium is released all at once, resulting in deep carved sections.

As a laser's wavelength becomes shorter, its energy and absorption rate generally get higher. For example, a copper plate (Cu) only absorbs 10% of fundamental (1064 nm) laser light. However, the absorption rate of UV light is 50-60%.

[How Green Lasers and UV Lasers Are Created]

Green lasers are often called second harmonic generation (SHG) lasers. 1064 nm light is passed through a single oxide crystal (LBO: Lithium Borate), and between 30-40% is converted to the 532 nm wavelength.

UV laser light is produced by combining 532 nm light with 1064 nm light and then passing both through another crystal. As a result, UV lasers are sometimes called third harmonic generation (THG) lasers. Fourth harmonic generation is referred to as D (Deep) UV and produces 266 nm light.

Abbreviated form of Light Amplification by Stimulated Emission of Radiation. Lasers have the following qualities:

1. (1) Monochromaticity - A pure, single wavelength of light.
2. (2) Excellent directionality - A parallel beam that advances without spreading.
3. (3) High coherence - Uniform light phases.

A comparison of ordinary light and laser light

Lasers emit beams of light with high directivity, which means that the component light waves travel together in a straight line with almost no spreading apart.
Ordinary light sources emit light waves that spread apart in all directions.
The light waves in a laser beam are all the same color (a property known as monochromaticity). Ordinary light (such as the light from a fluorescent bulb) is generally a mixture of several colors that combine and appear white as a result. As the light waves in a laser beam travel, they oscillate with their peaks and troughs in perfect synchronization, a characteristic known as coherence. When two laser beams are superimposed on each other, the peaks and troughs of the light waves in each beam neatly reinforce each other to generate an interference pattern.

	Directivity (light waves travel in straight line)	Monochromaticity	Coherence
Ordinary light
Laser beam

The source material that produces a laser. Laser mediums include solids, liquids and gases because different sources will produce different beam characteristics.

Processing performed using a laser.
Primary applications include micro-processing, welding, marking, and cutting.

Types of Laser Processing

Laser processing applications fall into three categories: removal, bonding and surface reforming.

Removal processes

Heating a material above its boiling point to evaporate parts off.

• Cutting
  Cutting thin metallic or non-metallic objects
• Drilling
  Drilling miniscule holes
• Scribing
  A method of scoring materials to make them easier to separate into smaller pieces. Typically involves grooving and separating IC chips.
• Trimming
  Removing portions of thin film. Commonly used to fine-tune semiconductors.
• Marking

Bonding processes

Heating a material above its boiling point to cause fusion.

• Welding
  High-speed metal welding

Reforming processes

Heating a material below its boiling point to improve it.

• Tempering
  Improves material wear-resistance and strength
• Vapor deposition
  Improves material wear-resistance and corrosion-resistance

The mirror that passes an emitted laser beam that has been amplified within the resonator.

Oscillation Environment

In laser oscillation, a state where "the number of high-level atoms is greater than the number low-level atoms" is called population inversion.

Structure

The structure of a gas laser oscillator seals gas in. It is also equipped with an electrode that produces the charge needed in order to generate population inversion and has optical resonators installed on both sides of its tube.

Oscillation Principles

When a rated electrical current is passed through the laser tube and discharged, it creates strong plasma within the tube and that plasma collides with other atoms to create an excited state. Between optical resonators constructed from a pair of reflective mirrors that possess extremely high reflectivity for the wavelength of the laser, the light is amplified as it goes back and forth, and is reflected on one side of a reflective mirror whose reflectivity is around 99%, resulting in the external emittance of laser light.

Oscillation involving a laser light that is produced in flashes. Pulse oscillation controls laser output by changing the oscillation frequency, making it possible to increase the amount of energy per single pulse. The values that express laser output are average output, peak output, and pulse energy. Their units are W (watts) and J (joules). Compared to the output value of a continuously oscillating laser, the peak output value for a pulse laser is high. However, average output is a number value that has added the oscillation frequency to the product of pulse width and peak output, making the average output power low. Even when the average output is a few W (watts), the peak energy of a pulse laser is +10 kW (kilowatts). This gives pulse lasers energy to mark and process metals.

In short, a laser made using semiconductor material. The activation layer between the p-n junctions generates light when p-side holes combine with n-side electrons.

The semiconductor's crystal (activation layer) amplifies the light and is structured to prevent it from leaking out. Semiconductor lasers are generally used for communications, optical disks, and laser excitation sources.

The structure is very similar to a diode’s. The only difference is the use of GaAs as the host, in which the energy takes the form of light instead of heat, and changes the diode into an LED (light-emitting diode).

A method where excitation light is irradiated and energized from the side of the laser medium.

A method of excitation by emitting excitation light from the area surrounding the side of the laser crystal. In this method, it is difficult to transfer heat to the center and heat cannot be transferred evenly to the whole medium.

A laser beam that has been collected to a single point in its cross section and has the characteristics of transverse mode points.

A phenomenon where excited atoms are hit with light, inducing photon generation and causing a chain reaction resulting in light emission.

Light that is visible to the human eye, measuring in wavelength from 380 nm to 780 nm.

What is Light?

Light is a type of "electromagnetic wave". "Electromagnetic waves" follow a standard of "wavelength" and starting from those of long wavelengths, can be divided into radio waves, infra-red rays, visible rays, ultra-violet rays, X-rays, and gamma rays.

What is Color?

As wavelengths of light hit an object, wavelengths that are reflected without being absorbed by the object are taken in by the human eye (retina). When this occurs, we recognize these wavelengths as the "color" of the object. The refractive index differs depending on the wavelength, therefore light is split. As a result, we are able to recognize a wide variety of "colors". For example, an apple reflects red wavelengths of light (600 to 700 nm) and absorbs all other wavelengths of light.
*Black objects absorb all light and thus appear black.

What is visible light?

The spectrum ranging from "red" to "purple" is referred to as "visible light". Also, longer wavelengths of light that are located in a region that is undetectable to the human eye are called "infrared light". Those on the shorter side are called "UV (ultraviolet) light".