排序方式: 共有50条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
5.
6.
A metal-metal waveguide quantum cascade laser with an abutted silicon hyperhemispherical lens is demonstrated at ~4.1 THz. The device produced 145 mW of peak pulsed power at 5 K with a wall-plug power efficiency of 0.7%, lasing up to a maximum operating temperature of 160 K. The far-field beam pattern has a full width at half-maximum value of ~4.8 degrees in the H plane. The same device produced ~26 mW of peak power using a Winston cone instead of a lens, lasing up to 165 K. The large increase in output power is mainly attributed to an increase in collection efficiency. 相似文献
7.
Zudov MA Ponomarev IV Efros AL Du RR Simmons JA Reno JL 《Physical review letters》2001,86(16):3614-3617
We report on a new class of magnetoresistance oscillations observed in a high-mobility two-dimensional electron gas (2DEG) in GaAs-Al(x)Ga(1--x)As heterostructures. Appearing in a weak magnetic field ( B < 0.3 T) and only in a narrow temperature range ( 2 K < T < 9 K), these oscillations are periodic in 1/B with a frequency proportional to the electron Fermi wave vector, k(F). We interpret the effect as a magnetophonon resonance of the 2DEG with leaky interface-acoustic phonon modes carrying a wave vector q = 2k(F). Calculations show a few branches of such modes existing on the GaAs-Al(x)Ga(1--)xAs interface, and their velocities are in quantitative agreement with the observation. 相似文献
8.
We have performed time differential perturbed angular correlation measurements on99Ru impurities in hexagonal beryllium metal over a temperature range from 77K to 808 K. The observed quadrupole interaction frequency decreases with temperature and is consistent with aT
3/2 power law dependence. 相似文献
9.
10.
Y. J. Wang Y. A. Leem B. D. McCombe X. -G. Wu F. M. Peeters E. D. Jones J. R. Reno X. Y. Lee H. W. Jiang 《Physica E: Low-dimensional Systems and Nanostructures》2000,6(1-4)
Electron cyclotron resonance (CR) has been studied in magnetic fields up to 32 T in two heavily modulation-δ-doped GaAs/Al0.3Ga0.7As single quantum well samples. Little effect on electron CR is observed in either sample in the region of resonance with the GaAs LO phonons. However, above the LO-phonon frequency energy ELO at B>27 T, electron CR exhibits a strong avoided-level-crossing splitting for both samples at energies close to ELO+(E2−E1), where E2, and E1 are the energies of the bottoms of the second and the first subbands, respectively. The energy separation between the two branches is large, reaching a minimum of about 40 cm−1 around 30.5 T for both samples. This splitting is due to a three-level resonance between the second LL of the first electron subband and the lowest LL of the second subband plus an LO phonon. The large splitting in the presence of high electron densities is due to the absence of occupation (Pauli-principle) effects in the final states and weak screening for this three-level process. 相似文献