摘要:

We report that inBaTiO3:Rhthe carrier-type depends not only on the postprocessing condition but also on the incident wavelength in two beam coupling. Carriers are the holes for the as-grown sample, and change to electrons for the sample reduced in the atmosphere of10−14 atmoxygen partial pressure. However, for the sample reduced in the atmosphere of10−10 atmoxygen partial pressure, the carrier is an electron for the incident wavelength of 514 nm, and a hole for 633 nm. Its absorption, photoinduced absorption, and two beam coupling are investigated and discussed. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121321

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A method of analysis of spectroscopic ellipsometry (SE) measurement data is proposed forAlxGa1−xN/GaNheterostructures grown on sapphire substrates. The SE data measured at three angles of incidence, 40°, 50°, and 60°, are simultaneously fitted assuming the dielectric function to consist of a Sellmeir dispersion equation and a free-exciton absorption term. The refractive indexnand the extinction coefficientkof undopedAlxGa1−xNfilms are determined in the spectral range of 1.5–4.13 eV of photon energy. The transition energy of the free exciton, which is in excellent agreement with the reported results for GaN in a previous paper, is found to vary from 3.44 to 3.95 eV when the compositionxvaries from 0 to 0.151. The refractive indexnofAlxGa1−xNhas also been compared with those reported results. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121322

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We report the measured finesse value of∼390in nonabsorbingAlxOy/AlGaAscavities. The nonabsorbing cavity consisting of a bottomAlxOy/AlGaAsdistributed Bragg reflector (DBR), anAlxOyspacer layer, and a topAlxOy/AlGaAsDBR is prepared by a wet-oxidation process. The measured resonance linewidth agrees well with that of calculation, indicating very small overall losses in the cavity. The wet-oxidation process does not seem to degrade the interface of the epitaxial layers significantly. The lower bound of maximum achievable reflectivity from theAlxOyDBR is estimated to be>99.95&percent;,assuming an average interface roughness of about 0.6 nm. The maximum achievable finesse of this type of cavity is expected to be larger than that of the all-epitaxial counterpart assuming the same roughness. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121323

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We have demonstrated efficient soft x-ray generation from femtosecond laser plasma created on a neodymium-doped glass target. Nd ions doped in glass target enhanced soft x-ray emission near 8 nm without broadening the soft x-ray pulse duration when there is no prepulse. A weak prepulse caused strong enhancement in soft x-ray intensity at 8 nm. By introducing a prepulse at 50 ns before the main pulse, 1&percent; energy conversion efficiency from laser pulse into soft x-ray at8±0.5 nmwas achieved by using a neodymium-doped glass target. This value is 1.2 times as high as that for Nd metal target case. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121324

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We report on a technique of passivelyQswitching an Er:YAG laser operating at 2.94 &mgr;m. TheQswitch consists of a high refractive index prism having one total internal reflection surface in contact with an absorbing liquid. The initial losses were achieved via attenuated total reflection. Using the aboveQswitch, pulses with up to 85 mJ having 130–140 ns pulse width were generated. The output was linearly polarized and the spacial beam profile was nearTEM00.The laser was operated at 2 Hz repetition rate. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121325

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A semiconductor laser diode in a photon cavity containing a mirror whose optical bandwidth is less than the classical cavity mode spacing can have multiple lasing states at the same bias current. The physics determining the behavior of this nonlinear multistate device is self-consistency between photon number, carrier number, and refractive index. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121326

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We describe efficient electroluminescence from a terbium complex, tris-(1-phenyl-3-methyl-4isobutyryl-5-pyrozolone)-bis(triphenyl phosphine oxide) terbium (PTT). The green-emitting material possesses much higher photoluminescence efficiency compared to the commonly used green light emitter, 8-hydroxyquinoline aluminum (ALQ). The rarely observed emission from the hole transport layer,N, N′-bis (3-methylphenyl)-N, N′-diphenyl-benzidine(TPD) of the device ITO/TPD/PTT/Al proves that PTT also is a good electron transporting material. The ITO/TPD/PTT/ALQ/Al device shows luminance up to920cd/m2at a drive voltage of 18 V and a luminous efficiency of 0.51 lm/W at a current density of 0.70mA/cm2,which are up to now the highest among devices using rare-earth complex materials as emitters. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121327

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

An external differential quantum efficiency exceeding 200&percent; has been observed from 4 &mgr;m InAs/InGaSb/AlSb interband cascade lasers under 1 &mgr;s pulses and 0.1&percent; duty cycle at 80 K. By increasing the pulse lengths and the repetition rates, average powers>16mW have been measured with 5 &mgr;s pulses at 10&percent; duty cycle, the internal quantum efficiency and the internal loss are determined to be 220&percent; and 14cm−1,respectively. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121265

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Far-field intensity distribution of semiconductor microdisk lasers is experimentally measured and the emission angle is found to be much smaller than that of a planar source with the same near-field width. In fact the emission angle is determined mainly by the disk radius instead of the disk thickness. A scalar diffraction theory in the cylindrical coordinate is developed to explain such an emission-angle-narrowing phenomenon and numerical calculation based on a vectorial diffraction theory is carried out to explain the measured polarization state. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121328

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The low voltage properties ofZnS:AgandSrGa2S4:Ce3+have been investigated for applications in field emission displays. It was observed that althoughZnS:Ag,Clhas slightly better chromaticity thanSrGa2S4:Ce3+,the high luminous efficiency, fast decay time, and better saturation behavior of the thiogallate potentially make it a very important blue phosphor. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121266

出版商:AIP    

年代:1998

数据来源: AIP