Laser terahertz emission microscope

Developments of laser terahertz (THz) emission microscope (LTEM) systems are reviewed. Ferntosecond lasers can excite the THz wave emission from various electronic materials, such as semiconductors, high-temperature superconductors, manganites, multiferroic oxides, etc., due to ultrafast current modulation. Limiting the topic to semiconductors, the current modulation is realized by acceleration or deceleration of photoexcited carriers due to the local electric field extrinsically or intrinsically induced at the laser illumination spot. Thus, LTEM has a potential to, visualize the local electric field distribution and photoresponse without any contacts or damages. we have ever constructed prototype free-space type and scanning fiber-probe (SFP) type LTEM systems with transmission or reflection mode. The system performance of the SFP-LTEM has been greatly improved compared with that for the prototype one. The spatial resolution of the SFP-LTEM system has a minimum spatial resolution less than 3 gm, which is defined by the laser beam diameter. The compact SFP-LTEM system, in particular the reflection system, has the potential to be utilized for wide applications as well as various materials. in this review paper, we introduce the details of the LTEM systems and example applications for the evaluation of electric field distribution in integrated circuits and supercurrent distribution in high-temperature superconductors.

本文综述了激光太赫兹（THz）发射显微镜（LTEM）系统的发展。飞秒激光能够由于超快电流调制而激发各种电子材料（如半导体、高温超导体、锰氧化物、多铁性氧化物等）发射太赫兹波。将主题限于半导体，电流调制是通过在激光照射点处外源性或内源性诱导的局部电场使光激发载流子加速或减速来实现的。因此，LTEM有可能在无任何接触或损伤的情况下可视化局部电场分布和光响应。我们曾经构建了具有透射或反射模式的自由空间型和扫描光纤探针（SFP）型LTEM原型系统。与原型系统相比，SFP - LTEM的系统性能有了很大提高。SFP - LTEM系统的空间分辨率最低可达小于3μm，这是由激光束直径决定的。紧凑的SFP - LTEM系统，特别是反射系统，有可能被广泛应用于各种材料。在这篇综述文章中，我们详细介绍了LTEM系统以及在评估集成电路中的电场分布和高温超导体中的超导电流分布方面的应用实例。