Quantum Dot Lasers for Long Wavelength Radiation

9628973 Bhattacharya各种应用都需要长波或太赫兹光源。一般说来，这种源已经在小带隙半导体中实现，最近又通过量子阱中的子带间跃迁实现。一般来说，如果要通过载流子注入势垒能在量子阱中产生带内布居反转，电子的带内能量弛豫时间是必要的。此外，带隙电子-空穴复合时间应较短。亚2维结构(量子点)的使用使我们可以将带内能量弛豫时间从体相或准2维体系的大约1皮秒增加到室温下的数百皮秒。此外，通过将这些结构放置在高相干光子密度的光腔中，有可能通过受激发射来减少带隙电子-空穴复合时间。我们的理论研究表明，这种系统在室温下可以实现强的布居反转和增益。我们将进行仔细的实验研究，以制造量子点结构来实现这些概念。我们已经演示了掩埋量子点波导结构的制作。我们预计这些设备将产生10^13至10^14赫兹的辐射。***

9628973 Bhattacharya There is a need for long wavelength, or terahertz, sources for a variety of applications. In general such sources have been realized with small bandgap semiconductors and more recently with intersubband transitions in quantum wells. In general, if intra-band population inversion is to be created in a quantum well by carrier injection at the barrier energy, it is necessary that the electron intra-band energy relaxation times are long. Additionally the bandedge electron-hole recombination times should be short. The use of sub-2 dimensional structures (quantum dots) allows us to increase the intra-band energy relaxation time from about a picosecond for bulk or quasi-2 dimensional systems to several hundred picoseconds at room temperatures. Furthermore, by placing these structures in a high coherent photon density optical cavity, it is possible to decrease the bandedge electron-hole recombination times through stimulated emission. Our theoretical studies show that strong population inversion and gain are possible at room temperature with such systems. We will carry out careful experimental studies to fabricate quantum dot structures to realize these concepts. We have already demonstrated the fabrication of buried quantum dot waveguide structures. We expect the devices to produce radiation in the range of 10^13 to 10^14 Hz. ***