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Transverse Mode Selection

Lecture



Transverse Mode Selection

It consists in receiving single-mode mode.

one). Selection method of controlling the Fresnel number.

  Transverse Mode Selection

  Transverse Mode Selection .

It is known that the Fresnel number controls the diffraction loss.

  Transverse Mode Selection .

  Transverse Mode Selection

  Transverse Mode Selection .

With a change in the size a of the aperture, as follows from the figure, the diffraction losses of the fundamental mode decrease, but naturally the radiation energy decreases.

2). Selection using the reflection coefficient of the mirror, the reflection coefficient of which repeats the shape of the mode to be selected.

  Transverse Mode Selection

3). Selection using RUF.

In the far zone, the radiation is the FS in the coordinate. Consequently, limiting the angular spectrum, we can select the transverse modes, since each transverse mode has its own spectrum.

  Transverse Mode Selection .

  Transverse Mode Selection

  Transverse Mode Selection

PV angles (PV spatial frequencies).

b << a   Transverse Mode Selection

FNU (FNPCH).

  Transverse Mode Selection

PPPF (PPUF).

  Transverse Mode Selection

  Transverse Mode Selection .

  Transverse Mode Selection

Disadvantage: multi-wave system (multilobe pattern).

Another type of angular resonant filter is presented in the following figure.

  Transverse Mode Selection

  Transverse Mode Selection .

The crossed filter allows you to get rid of side lobes.

four). Open resonator as a filter in a reflective device.

Due to the imposing devices, it is possible to obtain a single-mode regime in a wave-like resonator, which corresponds to the dielectric waveguide mode.

five). Telescopic resonator.

  Transverse Mode Selection

6). Gaussian filter.

  Transverse Mode Selection

  Transverse Mode Selection .

Gaussian filter is widely used in cellular communication (the impulse is obtained of a bell shape).

created: 2014-09-11
updated: 2021-03-13
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Quantum electronics

Terms: Quantum electronics