摘要:

We have investigated the effects of strained‐layer structures on the reduction of the threshold current density of AlGaInP/GaInP visible laser diodes. It was found that a remarkable reduction of the threshold current density could be realized by incorporating strained single quantum well structures in their active regions. The minimum threshold current density at room temperature under pulsed conditions is 215 A/cm2, which is by far the lowest value ever reported for AlGaInP/GaInP visible lasers and comparable to those of AlGaAs/GaAs lasers.

ISSN:0003-6951    

DOI:10.1063/1.104492

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Band‐structure analysis using the tight‐binding method indicates that there is a significant dependence of lasing properties of GaAs/AlGaAs quantum well lasers on substrate orientation, which suggests the importance of choosing the substrate orientation carefully for improving lasing properties. These results are mainly due to changes in thein‐planeeffective mass of the heavy hole.

ISSN:0003-6951    

DOI:10.1063/1.104466

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Reported here is a new fabrication technique for forming channel waveguides in organic electro‐optic (EO) polymer materials. The process uses projection printing to directly expose inverted ridge channel patterns in a UV curing optical epoxy cladding layer. This technique is noncontact, requires no post processing, minimizes wall roughness, and can be used with any spin coatable EO polymer. Single‐mode channel waveguides have been demonstrated and characterized as well as phase modulator devices.

ISSN:0003-6951    

DOI:10.1063/1.105210

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We describe the interaction of light pulses with a GaAs/AlAs resonant tunneling structure. We demonstrate that light with an average power of less than 10 &mgr;W can induce switching, and show that switching is accompanied by a change in the optical absorption. These results suggest a number of new applications for the resonant tunneling structure, including light‐by‐light switching.

ISSN:0003-6951    

DOI:10.1063/1.104467

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We have fabricated and operated large two‐dimensional (2D) arrays of phase‐locked surface‐emitting semiconductor lasers. The arrays were fabricated by reactive ion beam etching of epitaxial Fabry–Perot resonators comprising GaAs/AlGaAs quantum wells surrounded by AlAs‐AlGaAs quarter‐wave mirrors. Different arrays corresponding to different pixel size (2–5 &mgr;m) and spacing (1–2 &mgr;m) were produced to investigate evanescent coupling between pixels. The arrays were photopumped so that the array size could be conveniently varied from 1×1, 2×2,... up to 20×20. Except for the 1×1 which emits a circular pattern, all arrays exhibit a well‐defined four‐lobed far‐field pattern in agreement with our theoretical analysis of the optical modes which predicts domination by the 2D out‐of‐phase eigenmode. As a consequence this pattern can be understood with simple Fraunhofer diffraction theory. The angular spread of the lobes, determined by the periodicity of the array elements, is 10° for the array with element size/spacing of 4/1 &mgr;m. The widths of the lobes are 6.7° for the 2×2 and narrow to 3.2° with increasing number of pixels in the array. The array exhibits a sharp onset for lasing, operation on a single longitudinal mode, and a linewidth which narrows to ∼1 A˚ with increasing array size. The differential power efficiency is as high as 70%. These observations provide further impetus and guidance for the development of 2D laser diode arrays.

ISSN:0003-6951    

DOI:10.1063/1.104468

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The line‐focus‐beam acoustic microscope system is applied to investigate the elastic properties of LiTaO3. Elastic inhomogeneities are detected quantitatively as a significant variation of leaky surface acoustic wave (LSAW) velocities inX‐112.2°YLiTaO3wafers. Large changes, about 2.5%, in LSAW velocities are observed in some wafers, which correspond to a difference between the velocities for single and multidomains. One of the causes is found to be in the poling process during wafer fabrication.

ISSN:0003-6951    

DOI:10.1063/1.105217

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

A radio frequency (rf) biased electron cyclotron resonance (ECR) plasma etching technology has been developed to realize an efficient ion acceleration in high density and uniform ECR plasma for accurate Al‐Si‐Cu alloy film etching. In this technology, the substrate is located at the ECR position (875 G position) and the etching is carried out with a 400 kHz rf bias power. This Al‐Si‐Cu etching technology achieves a high etching rate (more than 5000 A/min), excellent etching uniformity (within ±5%), highly anisotropic etching, and Cu residue‐free etching in only Cl2gas plasma. These etching characteristics are accomplished by the combination of the dense and uniform ECR plasma generation at the ECR position with the efficient accelerated ion flux at the ECR position by using 400 kHz rf bias.

ISSN:0003-6951    

DOI:10.1063/1.104469

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The work presented describes the characteristics of single stage and severed high‐efficiency, high‐power traveling‐wave tube amplifiers operating inXband at 8.76 GHz. Average amplified output powers of 210 MW have been achieved at 24% efficiency. At high output power levels (≳100 MW) sidebands develop increasing the average radiated power to over 400 MW with a microwave conversion efficiency of over 45%. In single frequency operation phase stability to within ±8° has been demonstrated.

ISSN:0003-6951    

DOI:10.1063/1.104470

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Temperature dependences of reflection high‐energy electron diffraction intensities are measured for Si(111)‐7×7 clean surfaces. The temperature dependences of diffraction intensities for both 7×7 super spots and specular spots change above 830 K. These show the possibility of two states in the 7×7 structure. The high‐temperature phase of the 7×7 structure is stable up to 1090 K, following the well known phase transition between 7×7 and 1×1 structures.

ISSN:0003-6951    

DOI:10.1063/1.104471

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Thermal stability of PtSi contact to epitaxial Ge0.5Si0.5/(100)Si has been investigated. The PtSi layer remained structurally and morphologically intact on the epitaxial Ge‐Si alloy at temperatures around 650 °C. When annealed at higher temperatures, PtSi penetrated locally into the alloy, although no chemical reaction was observed. The observed stability of PtSi is explained on the basis of a ternary Pt‐Ge‐Si equilibrium phase diagram. Other choices of contact compounds on Ge‐Si alloys are also discussed.

ISSN:0003-6951    

DOI:10.1063/1.104472

出版商:AIP    

年代:1991

数据来源: AIP