The Study Of Terahertz Surface Emitting Distribution Feedback Quantum Cascade Lasers

Terahertz wave is an important electromagnetic wave without further development, and it can be used in different fields such as imaging, environmental monitoring, safety testing, etc. Featured many advantages for instance high energy conversion efficiency, small size, lightweight, centrality and so on, Terahertz quantum cascade laser(THzQCL) has become one of the important THz radiation sources. The combination of THz-QCL and distributed feedback grating(DFB) is an effective method for emiting single longitudinal mode laser. Although there are various achievements about THzDFB-QCL studies, in the surface emission DFB-QCL based on the 2nd DFB, the effect of the grating structure on the mode competition and laser power efficiency hasn't been issued in depth and systematical forms. Therefore, pointing at the above issue, the paper will carry out a research with theoretical and experimental skills as following.1) Inductively coupled plasma etching(ICP)which also regarded as the crucial technology has optimized bimetallic waveguide laser device. Besides, the ridge sidewall smooth ICP etching conditions have been provided, which effectively reducing the random scattering of side wall.2) THz-DFB-QCL device is available by virtue of original laser material produced by our laboratory. Therefore, characteristics of THz-DFB-QCL laser such as spectral, current- voltage- power, etc can be reflected deeply and systematically.3) Research suggested that lasers operate stably in longitudinal and transverse fundamental mode in DFB structure in the whole dynamics field. Transverse fundamental mode is generated when both sides of the border effectively improve highorder transverse mode's loss. Meanwhile, longitudinal fundamental mode is formed mainly because of the large overlap and similar frequency between the resonant cavity mode and the higher order longitudinal mode. Thereby, hole-burning effect can be effectively avoided in space and frequency fields.4) Research has indicated that radiation loss of the laser can be minimized with the increase of the slit number of the distributed feedback grating, which leads to maximum operating temperature increasing and the threshold current density decreasing accordingly as well. However, the output power efficiency of laser is reduced. On the other hand, the more grating slit numbers, the stronger input power of the lase is. Two opposing effects lead to maximum output power available as long as specific numbers of grating periodicity is set.