Structure of a quantum device

Figure 1 - Structural diagram of a quantum device

• AE - the active element

• LN - pumping lamp,

• PI - power supply,

• 3 - feedback element.

K _{F is the} full gain.

The postulates of Einstein. Quantum two-tier

system.

Figure 1-Quantum two-level system.

N _1, N ₂ - level population,

p is the volume specific gravity.

The first postulate of Einstein.

The probability of induced transitions is different from 0 only for the external field at the frequency

The second postulate of Einstein.

The quanta of the electromagnetic field, emitted during induced transitions, will be completely identical (coherent) to the quanta of the external field in terms of frequency, phase, direction.

where W _{12 is the} probability of absorption,

W ₂₁ - the probability of radiation,

B ₁₂ - absorption coefficient

B ₂₁ - emissivity.

The induced absorption and radiation is related to the external field. The probability of spontaneous radiation does not depend on the external field, but is determined by the expression:

We will find out under what conditions the induced radiation takes place: