电子科学与技术专业英语2. 3 Microwave and Photonic Devices.ppt

Specialized English School of Physics Optoelectronic Engineering W. Zhang Chapter 2 Semiconductor Device Table 2-1 summarizes the representative microwave devices and their operational principles. In this chapter, we consider four special microwave devices: the tunnel diode, the IMPATT diode, the BARITT diode, and the transferred-electron device. We shall investigate the operational principles of these devices and how they can be used in microwave applications.  Photonic devices are devices in which the basic particle of light-the photon-plays a major role. In this chapter we consider four groups of photonic devices: light-emitting diodes (LEDs) and diode lasers (light amplification by stimulated emission of radiation), which convert electrical energy to optical energy; photodetectors, which electronically detect optical signals; and solar cells, which convert optical energy into electrical energy. 可见光范围近似为0.4μm到 0.7μm, 紫外光范围为0.01μm 到 0.4μm, 红外光范围为0.7μm 到1000μm.  这章中主要感兴趣的范围是从近紫外(~0.3μm) 到近红外(~1.5μm)。 To convert the wavelength to photon energy, we used the relationship There are basically three processes for interaction between a photon and an electron in a solid: absorption, spontaneous emission, and stimulated emission. We shall use a simple system to demonstrate these processes. Consider two energy levels E1 and E2 of an atom, where E1 corresponds to the ground state and E2 corresponds to an excited state (Figure2-14), Any transition between these states involves the emission or absorption of a photon with frequency h v 12 given by h v 12 =E2-E1.At room temperature, most of the atom in a solid are at the ground state. This situation is disturbed when a photon of energy exactly equal to h v 12 impinges on the system. An atom in state E1 absorbs the photon and thereby goes to the excited state E2. The change in the energy state is the absorption process, shown in Figure 2-14a.The excited state of the atom is unstable;