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Instructions for Use
Surgical Laser Unit Limax
4
Description of the Unit
4.1
General Information on Laser Theory
LASER is an acronym meaning "Light Amplification by Stimulated Emission of Radiation". The
laser (light source) consists of an active medium and an excitation source. This excitation
source "pumps" the electrons of the active medium from their normal state into a stimulated
energy state (high energy level). The medium then starts to return to its normal state
(transition to lower energy levels). In this process, photons are emitted. The laser light is then
reflected multiply in an optical resonator (laser cavity) consisting of a highly reflecting mirror
and a partially transparent one. At the same time, it is amplified by induced emission while
traveling back and forth between the mirrors. Through the semitransparent mirror, part of the
laser light is coupled out and subsequently used for medical purposes.
Main characteristics of laser light:
Highly parallel beams – very little beam divergence / spread.
Monochromaticity – light of a very narrow wavelength range, equivalent to a single color in
the spectrum of electromagnetic radiation.
Coherence – all photons emitted are in phase (in terms of both space and time).
The active medium (lasing material) can either be a gas, a liquid dye or a solid. Most gas
lasers consist of atoms or small molecules or a mixture of both. In the case of the solid-state
laser, the active medium consists of atoms or ions doped (bound) in a solid-state host crystal.
In the case of the dye laser, the active medium consists of molecules of a relatively high
molecular weight, dissolved in a liquid.
For the pumping energy that is needed, either direct current, high-frequency energy or – as in
the case of the solid-state laser – laser light is used. Under specific pumping energy conditions,
the so-called "population inversion" phenomenon can be observed with all of the above media.
This means that it is possible to induce laser light emission at a specific wavelength that is
characteristic for the active medium used. The high light intensity gain is achieved through
optical feedback by the mirrors of the laser resonator and through amplification by induced
emission each time the beam passes through the resonator.
4.2
The Nd:YAG Laser
The Nd:YAG laser is a solid-state laser which emits high-intensity laser light at a wavelength of
1,320 nm (belonging to the near infrared range of the spectrum). The medium used is a
cylindrical YAG (yttrium-aluminum-garnet) crystal doped (mixed) with Nd
ions). The intensive light of laser diodes is used as an excitation / stimulation mechanism to
generate the required "population inversion". The wavelength of the light produced by the
laser diodes matches perfectly with an excitation line of the absorption spectrum of the Nd
ions of the YAG host crystal. In order to increase the efficiency and total output of the YAG
laser, several laser diodes are positioned very closely to the laser crystal for direct, low-loss
illumination of the crystal. Adjusting the output power of the laser diodes allows for direct
control of the output power of the Nd:YAG laser.
V. 1.0
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60
3+
ions (neodymium
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25
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