PHYSICS ELECTRONIC DEVICES

The Physics of Electronic Devices and Circuits



The Physics of Electronic Devices and Circuits

This laser is a semiconductor multilayer structure of n-type (excess of electrons in the conduction band) and p (more holes in the valence band). The transition of an electron into the conduction band due to power supply (pumping) is connected to the opposite process of spontaneous recombination called the radiant. This process leads to the release of a photon. At sufficiently high current inversion may occur, allowing laser action trigger. The outer walls of the waveguide form Fabry-Perot resonators.

Waveguide layer has a thickness of about 2 microns, making it easier to achieve population inversion at low current, and its width is 10 microns. In connection with the diffraction result of this construction of the active layer are large beam divergence angles, different in the two sections (about 30 ° corresponding to a thickness of 2 microns and more than 5 ° for a width of 10 microns). In order to reduce the asymmetry of the additional beam optical systems (prismatic or cylindrical) with different magnification in these sections. The disadvantages of these lasers include a broader spectrum of radiation in comparison with the He-Ne laser and the strong influence of temperature changes on the power of the beam and the length of the generated wave. These defects can be eliminated (or at least significantly reduce) using the PSU expanded respectively from negative feedback. Currently, most produced widespread use of laser diodes has a built-in photocell that allows the measurement of the intensity of emitted light. Power system is a controlled current source which supplies a current of laser diode depending on the size of current flowing through the photodiode. Negative feedback makes them more light emitting laser, the shock is weaker power.

In photonics for the construction of information infrastructures. It is also used laser arrays placed on a common substrate. The diameters of the individual lasers can be of the order of several micrometers. Each of the lasers can be independently controlled electronically; hence the array of lasers formed along the surface structure near point sources of radiation. Semiconductor lasers are sources of coherent radiation, which feature a fully active semiconductor medium. They can be divided into two groups:

Semiconductor junction lasers (diode)

Semiconductor lasers made of homogeneous material.

The semiconductor laser radiation process is located in the area adjacent to the semiconductor diode junction. Laser action to occur, as with other lasers must be appropriate conditions, resulting mainly from the structure of energy levels. The semiconductors are considered states of semiconductors as a whole, and not the levels ...