摘要:

We investigate the spectral line shape of radiative intersubband transitions in a quantum well as determined by two factors: the electron scattering rate from states of given energy and the mass difference between the two subbands involved. The interplay between these factors leads to an essentially non‐Lorentzian form of the spectral line. We develop an analytic theory of the line shape and calculate the dependence of the intersubband optical gain in a quantum well on both the population inversion and the temperature. Under typical conditions, the effect of electron temperature on the gain is similar to that of the lattice temperature, which points to the importance of hot carrier effects in understanding the behavior of intersubband lasers. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116002

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We propose and demonstrate a new method to measure the two‐wave mixing coefficient with slight influence of beam fanning in thick crystals with high coupling constants. The strong beam fanning was suppressed by introducing an additional erase beam. By measuring the effective two‐wave mixing coefficient with the additional erase beam, the coupling coefficient without the additional erase beam can be calculated. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116003

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

An epitaxially grown ytterbium‐doped gadolinium gallium garnet (Yb:GGG) buried channel waveguide laser is prepared on an yttrium substituted GGG substrate (Y:GGG). The effective light guiding structure is obtained as a result of the difference of refractive indices of Yb:GGG and Y:GGG. The Yb:GGG waveguide exhibits single‐mode 1.025 &mgr;m lasing operation at room temperature. The incident threshold and slope efficiency of the 5‐mm‐long waveguide laser when pumped at 0.941 &mgr;m are 80 mW and 13.4%, respectively. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116004

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Anomalously large decrease in spontaneous emission is observed in gain‐guided vertical‐cavity surface‐emitting lasers after the onset of lasing. By analyzing two‐dimensional profiles of the lasing mode and carrier density, we found that this unexpected phenomenon originates from the contraction of transverse lasing mode size. Under the condition of the constant modal gain, it is explained that the above‐threshold average carrier density could decrease in contradiction to the general understanding. Unless this anomalous effect is taken into account properly, nontrivial errors could occur in determination of the external quantum efficiency. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116005

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Intervalence band absorptions of 1.5 &mgr;m light in various InGaAs/InGaAsP quantum well laser structures are investigated theoretically. The intervalence band absorption formalism based on 6×6 Luttinger‐Kohn Hamiltonian is developed. The absorption tends to decrease with the barrier height of quantum wells. The tensile strain in the well causes the absorption to reduce, while the compressive strain causes it to increase. Also is found that the absorption decreases with increase in temperature. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116006

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We report on high efficiency frequency‐conversion obtained by four‐wave mixing in a single traveling‐wave semiconductor optical amplifier. Efficiency in excess of 0 dB is demonstrated for frequency conversion up to 2 THz. Measurements of the signal to the amplified spontaneous emission background ratio are also presented. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116007

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Electron drift velocities in mixtures of SiF4and Ar have been measured using a pulsed‐Townsend type drift tube. A set of vibrational excitation cross sections of electron scattering in SiF4has been subsequently determined by the swarm analyses of measured transport data in highly dilute SiF4−Ar mixtures. The derived cross sections are consistent with the electron transport properties over an order of magnitude in SiF4concentration in gas mixtures, thus providing evidence that the main features of their near threshold behavior, and of their absolute magnitude have been captured. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116008

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We report an ionized‐cluster‐beam (ICB) deposition and the electrical bistability of C60–tetracyanoquinodimethane (TCNQ) thin films. The films are fabricated by using an ionized‐cluster‐beam deposition method in a high vacuum system. The as‐deposited films were characterized by transmission electron microscopy and optical absorption spectroscopy, which verified the formation of the charge‐transfer complex system in C60–TCNQ thin films and the microstructure of these thin films. The structure and the electrical property of the ICB deposited Ag‐TCNQ thin films are also presented. The possible conductive mechanism of these ICB deposited thin films is discussed in the letter. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116009

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

A new phenomenon of diamond growth was observed. (001) oriented diamond layers can be grown on a (111) diamond face in a bias‐assisted chemical vapor deposition process. The growth characteristics were investigated by means of scanning electron microscopy and Raman spectroscopy. It was found that, due to the ion bombardment, the epitaxial growth of the (111) diamond face was interrupted and a secondary nucleation occurred. This ion‐bombardment‐induced secondary nucleation leads to the growth of a top layer with a nonparallel orientation relationship with the substrate. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116010

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Epitaxial Mo/NbN superlattices were grown on MgO(001) substrates by reactive dc magnetron sputtering. The epitaxial relationship between the bcc metal and the NaCl (B1)‐structure compound is Mo(001) ∥NbN(001), Mo[110]∥NbN[010], and the lattice mismatch is 1.4% given the 45° rotation about the (001). Cross‐sectional transmission electron microscope images show well‐defined and relatively planar layers. High angle x‐ray diffraction results show up to 25 superlattice reflections extending over ≊30° in 2&thgr;. Kinematical model fits to the x‐ray diffraction data suggest that the interface widths were only ≊0.3 nm, presumably because of the immiscibility of Mo and NbN. Initial nanoindentation results indicate hardness values of ≊28 GPa, about 3 times the rule‐of‐mixtures value. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116011

出版商:AIP    

年代:1996

数据来源: AIP