Quantum Dot Lasers for Long Wavelength Radiation

9628973 Bhattacharya对于各种应用都需要长波长或太赫兹的源。一般来说，这种源已经用小带隙半导体实现，最近用量子阱中的子带间跃迁实现。一般来说，如果要在量子阱中通过在势垒能量处注入载流子来产生带内居数反转，则必须使电子的带内能量弛豫时间长。此外，带状电子-空穴复合时间应短。亚二维结构（量子点）的使用使我们能够将带内能量弛豫时间从体或准二维系统的约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学腔中，可以通过受激发射减少带隙电子-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种群反转和增益。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。我们已经演示了埋藏量子点波导结构的制造。我们期望这些装置产生的辐射频率在10^13到10^14赫兹之间。* * *

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. ***