Table of Contents
Advertisement
MCO25plus Operating Instructions
3
Description of the Unit
3.1
Some General Remarks on the Laser Principle
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 transforms ("pumps") the active medium from its normal state into a stimulated energy
state (high energy level). The medium then begins to return to its normal state (transition to
lower energy levels), and in this process photons are emitted. This radiation is optically
amplified with the help of an optical resonator consisting of a highly reflecting mirror and a
partially transmitting one. Via the partially transmitting mirror, part of the laser light is coupled
out and is then used for medical purposes.
The main characteristics of the laser light include:
1)
High degree of beam parallelism – very little beam divergence.
2)
Monochromaticity – light of a very narrow wavelength range, equivalent to a single
color in the spectrum of electromagnetic radiation.
3)
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 solid-state
lasers, the active medium consists of atoms or ions doped (bound) in a solid-state host crystal.
In the case of dye lasers, 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 solid-state lasers – a light source is used. Under specific pumping energy
conditions, the so-called "population inversion" phenomenon can be observed in all of the
above materials. This means that it is possible to induce laser light emission at a specific
wavelength characteristic of the active medium used. The high light intensity gain is achieved
by way of optical back-coupling, which means that the radiation emitted is reflected with the
help of (laser) mirrors (the optical laser resonator).
3.2
The CO
The continuous-wave (CW) CO
wavelength of 10,600 nm. The medium used is a CO
tube. As the tube has a relatively long life, gas refilling is required only after several thousand
operating hours. The direct-current discharge excites the gas molecules. The excited CO
turn, emits photons. The coherent light generated in the optical resonator exits the resonator
through the semitransparent output mirror and is then delivered through the articulated mirror
arm. The laser light intensity can be controlled via the electric energy pumped into the gas
discharge.
V 4.1
Laser
2
laser is a gas laser which emits high-intensity radiation at a
2
-N
-He gas mixture contained in a sealed
2
2
, in
2
19
Advertisement
Table of Contents
