摘要:

Nonlinear absorption at 248.5 nm is studied with an 8 ps pulse. Two‐photon absorption in fused silica and three‐photon absorption in CaF2are observed. Absorption coefficients are 8×10−11cm/W and 2×10−21cm3/W2for fused silica and CaF2, respectively.

ISSN:0003-6951    

DOI:10.1063/1.102417

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

We present experimental results on the photorefractive two‐beam coupling constant and response time of two Cr‐doped strontium barium niobate crystals with different dopant concentrations. Both showed significantly faster response times over Ce‐doped SBN:60, but with corresponding decreases in their coupling constants.

ISSN:0003-6951    

DOI:10.1063/1.102418

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

We describe a new surface‐emitting semiconductor structure, its fabrication, and its performance. Phase‐locked emission takes place from a region much larger than the wavelength in two dimensions; therefore we term this device a two‐dimensional coherent array. The key feature of our device is that the radiation is coupled directly from the active region using a nonresonant grating coupler, i.e., the grating is of noninteger order.

ISSN:0003-6951    

DOI:10.1063/1.101899

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

The lateral mode thresholds of an external cavity AlGaAs laser diode array are measured as a function of cavity length. It is found that certain cavity lengths induce the array to lase in either the fundamental or highest order lateral mode. The results are explained using the theory of Talbot self‐imaging in fractional Talbot planes

ISSN:0003-6951    

DOI:10.1063/1.101900

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

We have significantly improved the emission and detection of electromagnetic beams of single‐cycle 0.5 THz pulses, through the use of new dipolar antenna structures. The frequency response was extended to well beyond 1 THz, and the beam power was increased by more than 15 times. The antennas were located at the foci of sapphire lenses and were photoconductively driven by ultrafast laser pulses. An additional collimation by a paraboloidal mirror produced a beam with a 25 mrad divergence, and subsequent focusing by a second identical mirror improved the coupling between the transmitting and receiving antenna by orders of magnitude.

ISSN:0003-6951    

DOI:10.1063/1.101901

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

We report room‐temperature observation of Wannier–Stark localization in a GaAs/AlGaAs superlattice. We show that large modulation can be obtained over a wide spectral range and demonstrate the operation of a self‐electro‐optic effect device.

ISSN:0003-6951    

DOI:10.1063/1.101902

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

We report the results of an experimental study of the far‐field characteristics of InGaAsP edge‐emitting light‐emitting diodes. Our results show that the asymmetric structure in the transverse far‐field distribution of the device is caused by modes which are supported by the asymmetric dielectric waveguide. These modes propagate in the InP cladding layer with the higher refractive index at an angle to the fundamental mode. Their relative intensities, compared to the fundamental mode intensity, increase as the active layer thickness decreases below 0.1 &mgr;m, accounting for the observed concomitant decrease in the fiber‐coupling efficiency of these devices.

ISSN:0003-6951    

DOI:10.1063/1.101903

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

A deep ultraviolet cw laser has been used to form vias in a polyimide film. The etched features have smooth sidewalls and high aspect ratios. The observations are consistent with an etching mechanism based on thermal decomposition.

ISSN:0003-6951    

DOI:10.1063/1.101904

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

We report an all‐silicon fiber‐optic light modulator which relies on free‐carrier optical dispersion and mode filtering in single‐mode fibers. Greater than 10% peak‐to‐peak intensity modulation over a 200 MHz bandwidth for 10 mA rf current modulation at 1.3 &mgr;m wavelength is demonstrated.

ISSN:0003-6951    

DOI:10.1063/1.101905

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

The formation of crystalline diamond films from amorphous diamond‐like carbon films by pulsed laser irradiation with a 300 &mgr;s non‐Q‐switched Nd:YAG laser has been established by a combined study of transmission electron microscopy, x‐ray photoelectron spectroscopy, and electrical resistivity. The films have been prepared by glow discharge decomposition of a mixture of propane,n‐butane, and hydrogen in a rf plasma operating at a frequency of 13.56 MHz. Prior to laser irradiation, the films have been found to be amorphous by transmission electron microscope studies. After irradiation, the electron diffraction patterns clearly point out the formation of cubic diamond structure with a lattice spacing of 3.555 A˚. However, the close similarity between diamond and graphite electron diffraction patterns could sometimes be misleading regarding the formation of a diamond structure, and hence, x‐ray photoelectron spectroscopic studies have been carried out to confirm the results. A chemical shift in the C 1score level binding energies towards higher values, viz., from 286.5 to 287.8 eV after laser irradiation, and a high electrical resistivity >1013&OHgr; cm are consistent with the growth of diamond structure. This novel ‘‘low‐temperature, low‐pressure’’ synthesis of diamond films offers enormous potential in terms of device compatibility with other solid‐state devices.

ISSN:0003-6951    

DOI:10.1063/1.101906

出版商:AIP    

年代:1989

数据来源: AIP