摘要:

There are several interesting applications for a picosecond, far‐infrared (100–1000 &mgr;) free‐electron laser. One obstacle to its development is the slip that occurs between the electron beam and the radiation. This can be reduced by operating the laser in a parallel‐plane waveguide, and choosing the laser parameters and transverse guide dimension such that the group velocity of the wave nearly matches the axial velocity of the electrons. The laser wavelength depends on both the electron energy and the waveguide dimension, and the laser can be tuned by varying either. Both the tuning characteristics and the slip as a function of wavelength are different from those of a conventional free‐electron laser.

ISSN:0003-6951    

DOI:10.1063/1.103460

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Optical waveguide microscopy is introduced as a novel imaging technique that allows for the microscopic characterization of thin‐film samples by using guided optical waves as illumination light source. Excellent thickness (<1 nm) and good lateral resolution (<10 &mgr;m) is demonstrated. As a first application we image and analyze the two‐dimensional thickness profile of a planar polymeric spun‐on waveguide structure.

ISSN:0003-6951    

DOI:10.1063/1.103461

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

AlGaAs/GaAs surface‐emitting laser diodes (SELDs) with distributed Bragg reflectors (DBRs) and current blocking layers are fabricated with the combination of a two‐step epitaxial growth and the reactive ion beam etching (RIBE) technique. An Al0.1Ga0.9As/Al0.7Ga0.3As multilayer and an amorphous silicon (a‐Si)/silicon dioxide (SiO2) multilayer are employed for the lower and upper mirrors, respectively. The active region has a 5×5 &mgr;m or 4 &mgr;m &fgr; area and a 0.8 &mgr;m thickness. The minimum threshold current is 3.3 mA under pulsed condition and 4.1 mA under continuous wave (cw) operation at 12 °C with junction‐side‐up configuration. Stable single longitudinal mode is observed, and far‐field pattern (FFP) indicates higher transverse mode operation.

ISSN:0003-6951    

DOI:10.1063/1.104096

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Diode lasers emitting at 2.29 &mgr;m have been fabricated from lattice‐matched double heterostructures having a GaInAsSb active layer and AlGaAsSb confining layers grown by molecular beam epitaxy on GaSb substrates. For pulsed room‐temperature operation these devices have exhibited threshold current densities as low as 1.7 kA/cm2and differential quantum efficiencies as high as 18% per facet, the highest room‐temperature efficiency reported for any semiconductor diode laser emitting beyond 2 &mgr;m.

ISSN:0003-6951    

DOI:10.1063/1.103462

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We describe InGaAs/InP multiquantum well distributed feedback (DFB) lasers with novel properties atrributable to the quantum well based active layer. The low internal loss waveguide and shallow gratings have allowed the fabrication of lasers with a cavity length varying from 0.5 to 2 mm, and corresponding threshold currents of 22 and 100 mA, respectively. A mode rejection ratio as high as 50 dB has been obtained in lasers with one antireflection‐coated facet. The long cavity devices exhibit linewidths as low as 600 kHz at a power output of 35 mW. Transmission experiments through 70 km of fiber, at 1.7 Gb/s, showed a dynamic chirp penalty of only 0.25 dB, a factor of 8–10 smaller than in conventional lasers.

ISSN:0003-6951    

DOI:10.1063/1.103463

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A self‐pumped phase conjugate reflectivity of 74.8% is obtained with a suitably cut KNbO3:Fe crystal in a polygonal shape. The design and operation of this self‐pumped phase conjugator is described. The build‐up time is observed to be dependent on the input power. The phase conjugate nature of the retroreflected beam has been further confirmed by a significant decrease in the specular reflectivity of the input surface of the crystal.

ISSN:0003-6951    

DOI:10.1063/1.103464

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A nonlinear refractive indexn2.DANof a 4‐(N, N‐dimethylamino)‐3‐acetamidonitrobenzene (DAN) single‐crystal cored fiber of 3.9 mm length and 2.3 &mgr;m core radius is evaluated by observing the spectral broadening of a 250 fs pulse due to dispersive self‐phase modulation in its fiber and that in a conventional fused‐silica fiber. The result shows that the value of the femtosecond‐responsen2.DANin the nonabsorbing wavelength region around 625 nm is 1.7×104times as large as that of the latter’s glass fiber.

ISSN:0003-6951    

DOI:10.1063/1.103465

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A novel method for calculating the dispersion relation of electromagnetic modes in an arbitrary periodic slow wave structure is reported. In this method it is sufficient to know the frequencies corresponding to three special wave number values, with other points calculated using an approximate analytical expression. This technique was successfully applied to determine the dispersion relation of the TM01mode in a sinusoidally corrugated slow wave structure. This structure is commonly used in relativistic high‐power backward wave oscillators and traveling‐wave tubes, and is expected to have many additional applications.

ISSN:0003-6951    

DOI:10.1063/1.103466

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Thermally induced interactions of Cu with CoSi2, with and without interposed TiNxlayers, have been studied using Rutherford backscattering spectrometry, Auger electron spectroscopy, and x‐ray diffraction. Cu diffuses through a preformed CoSi2layer to form the structure Cu/CoSi2/Cu3Si/Si at temperatures above 300 °C, and no dissociation of CoSi2occurs. A 50 nm TiNx(x≊1) layer is observed to be an effective diffusion barrier up to about 500 °C between Cu and CoSi2.

ISSN:0003-6951    

DOI:10.1063/1.104230

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The threshold pump power of an AlGaAs‐GaAs ridge quantum well laser diode has been reduced by 42% by recycling the spontaneous emission. An integrated photodiode absorbs the spontaneous radiation emitted by the laser diode and converts it back into electrical power. The recycling of this power results in a reduction of the electrical power required to reach the lasing threshold.

ISSN:0003-6951    

DOI:10.1063/1.103467

出版商:AIP    

年代:1990

数据来源: AIP