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Types of lasers
- Carbon dioxide (CO2) laser
A discharge tube is formed between two opposed mirrors that comprise a resonator. A gas
mixture laser medium of CO2, N2 and He is injected into the discharge tube. The gas molecules
are excited by the discharge. The laser light resonates between the mirrors and is amplified. The
amplified light is removed from a partially transmitting mirror designed to transmit some of the
light.
- Fiber laser
The fiber laser is a laser that uses a fiber (waveguide) as laser oscillator. Mirrors are not used. A
diffraction grating, called the fiber Bragg grating (FBG), is formed. The FBG reflects particular
wavelengths of light and serves as the resonator mirror. Usually, a semiconductor laser is used
for excitation.
- Guide lasers (He-Ne laser and semiconductor laser)
A He-Ne laser is a gas laser that uses a He-Ne gas mixture as laser medium. Visible He-Ne
lasers are available in green, yellow and orange colors, depending on their wavelengths. A red
He-Ne laser is most popular.
A semiconductor laser consists of semiconductor PN junctions. When electric current is injected,
positively charged holes and negatively charged electrons combine to produce a laser light. The
laser light is passed back and forth in the resonator and amplified. Blue, blue violet and red
visible laser lights are produced, depending on wavelengths.
Visible He-Ne and semiconductor lasers are used as guide lasers for checking the cutting
position during setup, etc.
Hazards of lasers to human body
The carbon dioxide laser has a wavelength of 10.6 µm and is invisible to the human eye. The
CO2 laser light is absorbed well by water. When it enters the eye, it may burn the cornea. When
direct or scattered CO2 laser light shines on the skin, it may burn the skin.
Fiber lasers have a wavelength of 1.06 to 1.08 µm and are invisible to the human eye like CO2
lasers. When the fiber laser light strikes the eye, it passes through the cornea and lens. When
the light is focused on the retina by the lens action of the cornea and lens, it may do serious
damage to the retina. When the skin is exposed to direct or scattered fiber laser light, it may be
burned as done by the CO2 laser light. The burn may penetrate deeper.
He-Ne lasers and semiconductor lasers have a wavelength of 0.6 to 0.7 µm and are visible to
the eye. When these laser lights fall on the eye, they pass through the cornea and lens, and may
damage the retina.
On laser cutting machines that use the lasers described above, operator safety is ensured by
protective devices or shield devices composed of special windows to absorb specific laser light
wavelengths, safeguarding devices to provide a safety distance, and protective goggles to
protect the eyes. Every day, check all protective devices, safeguarding devices and personal
protective equipment for holes, burn marks and other defects.
(3) Types and hazards of lasers
Summary of Contents for Ensis 3015 AI
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