Technician's instructions KEY Laser III 1243
1 Overview of functions
|
1.1 Physical basics
If the energy that is fed to the oscillatory circuit by the amplifier is greater than the
loss in the oscillatory circuit, the signal in the oscillatory circuit greatly increases and,
as a result, so too does the output signal ②.
Theoretically, the output signal would become infinitely large; in reality, although
muffled by losses and absorption effects, the output signal reaches high levels ne‐
vertheless.
The feeding back of the amplifier results in the output signal being independent of
the input signal.
A self-exciting oscillator is thus formed from the fed back amplifier.
The self-excition in a fed back amplifier is created by the existing background noise
of the amplifier ①.
The laser works in much the same way as high frequency or radio technology.
Different components must be used because of the extremely high frequencies that
are obtained. A feedback loop 6/3 (HR and AR mirrors) is used to achieve an ex‐
tremely high total amplification (induced emission) even though the amplifier 1 is
usually weak.
Only the high total amplification can cause the oscillator (amplifier ① and feedback
loop ⑥/⑦) to make the transition to the self-excited state. The laser reaches this
state by itself due to its background noise (spontaneous emission).
This is when the laser becomes active.
The laser's amplifier ①, the laser medium, requires a suitable form of input energy
④ to achieve this.
The energy for this type of laser is supplied by the flashlamp ⑤. The process this
involves is termed “optical pumping“ and will be explained in more detail in a sepa‐
rate section.
A suitable substance must be chosen for the laser medium (see other section) in
order to obtain an effective amplifier in the resonator (induced emission).
An efficient feedback loop must also be implemented. Two mirrors (the HR and AR
mirrors) reflect the light emitted by the laser medium ① back into the laser medium.
This mirror arrangement makes up the optical resonator.
In the case of the KEY Laser, the laser resonator consists of two plane mirrors in a
parallel arrangement.
10/176
