Design and Prototype Construction of Infrared Resonance Scattering Tomography

由于红外光的散射强度取决于入射光引起的电子偏振或电子位移，半导体的光散射将分为以下三项：1.电子捕获在半导体晶体中的电子中心和/或缺陷引起的偏振。在这里，电子对它们的位移显示恢复力，然后它们有自己的共振频率，这是由电子的质量和恢复力决定的。半导体内部微小粒子中电子的极化，这将显示出类似于金属粒子内的等离子体共振的共振。自由载流子引起的偏振，由于对电子位移没有恢复力，将主要有助于吸收。如果改变被测样品的温度或入射红外光的频率，将会观察到上述第一类和第二类共振。不幸的是，我们没有任何频率范围为1微米的可调谐激光器。在这里，样品被安装在一个低温恒温器中，由冰箱将温度从室温改变到24K。温度的稳定性为0.1K。因此，我们在130K下用1.15微米的He-Ne激光清楚地观察到了In掺杂的GaAs晶体的共振型散射，这在实验上得到了证实。

Since scattering intensity of IR light is dependent upon electronic polarization or displacement of electrons cause by the incident light, the light scattering from semiconductors will be classified into the following three items:1. the polarization induced by electrons traped in electronic centers and/OR defects in semiconductor crystals. Here, the electrons show restoring force against their displacement and then they have their own resonance frequencies which are determined by the mass and restoring force of the electrons.2. the polarization due to electrons in tiny particles inside semiconductors, which will show a resonance similar to the plasma resonance inside metal particles.3. Polarization due free carriers, which will mainly contribute to absorption because of no restoring force against displacement of electrons.The resonance mentioned above the category 1 and 2 will be observed if we abjust temperature of the specimens to be examind or frequency of incident IR light. Unfortunately, we don't have any tuneable laser in the frequency range of 1 micron.Here, the sample is installed in a cryostat which temperature is changed by a refrigerator from room temperature to 24K. The stability of the temperature is 0.1 K. Thus, we have clearly observed resonance type scattering from an In-doped GaAs crystal at 130 K by 1.15mu m radiation of a He-Ne Laser, which was confirmed experimentally.