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Laser generators. Self-excitation conditions

Lecture



Laser generators. Self-excitation conditions

  Laser generators.  Self-excitation conditions

  Laser generators.  Self-excitation conditions

  Laser generators.  Self-excitation conditions

  Laser generators.  Self-excitation conditions

Due to the fact that the transverse dimensions are much larger than the length of the standing wave, the stationary field will have many types of colds *** that represent the stationary field distribution along the resonator and across. Their eigenvalues ​​depend on the geometry and type of stationary function. The distributions along the resonator are called TEM mng longitudinal mode. Each mode has its own frequency. This uneven distribution of the field in the far-field Fresnel gives the radiation pattern the appearance of pants. In the practice of using lasers they try to use the single-mode mode.

  Laser generators.  Self-excitation conditions

As you know the conditions of the excitation of the oscillator:

1) PIC availability   Laser generators.  Self-excitation conditions

2) Depth of communication   Laser generators.  Self-excitation conditions

Critical case when   Laser generators.  Self-excitation conditions i.e.   Laser generators.  Self-excitation conditions .

The laser resonator consists of two mirrors R 1 , R 2 form the usual collar *** circuit, which performs the selection in frequency and phase.

The smaller the size and the mirror the smaller the angle

1) Rays beyond the resonator carry energy and introduce additional diffraction losses.

  Laser generators.  Self-excitation conditions

2) Energy is accumulated in the cavity due to the interference of the forward and reverse waves.

3) The task of the resonator to form the spatial distribution of the field.

The resonator is characterized by good quality:

  Laser generators.  Self-excitation conditions

The larger the size of the resonator, the greater its quality factor due to the increase in energy.

The number of addition of waves in the resonator:

  Laser generators.  Self-excitation conditions

This is an indicator of how many times the wave interferes in the resonator until the amplitude decreases in   Laser generators.  Self-excitation conditions time.

Losses in the laser, reducing the quality factor:

1) Leaky laser. Radiation loss coefficient

  Laser generators.  Self-excitation conditions

  Laser generators.  Self-excitation conditions

2) Absorption loss in the material:

  Laser generators.  Self-excitation conditions

3) Loss of dispersion in the material:

  Laser generators.  Self-excitation conditions

4) Losses at the ends of the active elements:

  Laser generators.  Self-excitation conditions

  Laser generators.  Self-excitation conditions

5) Absorption loss in the mirror:

  Laser generators.  Self-excitation conditions ,   Laser generators.  Self-excitation conditions

Full phase shift:

  Laser generators.  Self-excitation conditions

  Laser generators.  Self-excitation conditions ,   Laser generators.  Self-excitation conditions ,   Laser generators.  Self-excitation conditions

Set the conditions for self-excitation of the laser, for which we use the design scheme:

  Laser generators.  Self-excitation conditions

We write the field equation after the passage of a wave in the resonator:

  Laser generators.  Self-excitation conditions (one)

If completely filled, then   Laser generators.  Self-excitation conditions

1) Phase condition of self-excitation:

  Laser generators.  Self-excitation conditions

2) Amplitude balance:

  Laser generators.  Self-excitation conditions   Laser generators.  Self-excitation conditions

  Laser generators.  Self-excitation conditions

  Laser generators.  Self-excitation conditions

  Laser generators.  Self-excitation conditions ,   Laser generators.  Self-excitation conditions

From equation (1) it follows that is a periodic function. In this case, equation (1) is performed for:   Laser generators.  Self-excitation conditions ;   Laser generators.  Self-excitation conditions

Note: with phase balance, we consider only waves traveling along the z axis.

  Laser generators.  Self-excitation conditions

  Laser generators.  Self-excitation conditions - Lorenz line, limiting the number of modes

  Laser generators.  Self-excitation conditions

  Laser generators.  Self-excitation conditions ,

  Laser generators.  Self-excitation conditions

Electromagnetic energy accumulation:

  Laser generators.  Self-excitation conditions


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Quantum electronics

Terms: Quantum electronics