Lasers Essay

772 Words 4 Pages
The substrate is rotated in the center of the growth chamber to ensure even growth on its surface and its angle can be manipulated depending on which effusion chamber shutter is opened. The time the substrate is exposed to an effusion chamber is calculated. Based on the area of the substrate, the pressure in the chamber and the molecular weight of the species, the shutter time is calculated to ensure the desired thickness of the film which will be adsorbed on to the substrate. For example, when using two semiconductors with similar lattice constants, such as InAs and GaAs, a quantum well can be fabricated in roughly three stages. In the first stage, the Gallium and Arsenic chambers are opened for a calculated duration. The Ga and As particles …show more content…
One type of lasers are solid-state lasers, which include semiconductor lasers and their derivative, the quantum well laser. Semiconductor lasers utilize the properties of a P-N junction of semiconductor material. This P-N junction is a connection of a p-doped (electron-hole-doped) semiconductor material and n-doped (electron-doped) semiconductor material. When electric current through this junction is present, the electrons participating in the electric current are of an elevated energy state and propagate in the conduction energy band. The conduction energy band exists at a higher energy than the valence band, which is where electrons occupy the valence states of an atom. In an electric current, it could also be interpreted that a flow of electron-holes (vacancies where electrons could occupy, having positive charge) flows in the opposite direction of the flow of electrons. In a semiconductor P-N junction, these electrons and holes are allowed to combine to emit a photon of light with energy equal to the difference of energies of the electron and hole. This emitted photon has a characteristic wavelength and frequency associated with this energy. Semiconductor P-N junctions can be engineered to emit photons of desired wavelengths and energies. However, the ability to engineer

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