摘要:

Low cw threshold current of 45 mA and high differential quantum efficiency of 78% have been achieved at room temperature in an (Al0.6Ga0.4As)2(GaAs)2superlattice quantum well laser emitting at 681 nm. The quantum well structure has been optimized to minimize the threshold current density at 680 nm. The new ridge‐waveguide structure with a current‐blocking supporting region is employed to reduce the thermal resistance.

ISSN:0003-6951    

DOI:10.1063/1.98895

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

The interband optical absorption of a nonuniform semiconductor quantum dot system is calculated. The effect of dot size variation on the resolvability of the absorption peaks is estimated. The dots are assumed to be cubic, with a size distribution described by a Gaussian function. It is shown that the total absorption spectrum of such a dot system depends strongly on the dot size distribution described by the parameter &xgr;, the ratio of the standard deviation of the dot size to the average dot size of the system. The range of &xgr; values for which the absorption peaks are resolvable is given.

ISSN:0003-6951    

DOI:10.1063/1.98896

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

A nonlinear directional coupling element consisting of a GaAs‐based multiple quantum well (MQW) heterostructure sandwiched between two slab optical waveguides is analyzed numerically with optical absorption losses in the MQW included. Optical waveguides are designed to be made of lossless AlGaAs slabs of an appropriate composition corresponding to the wavelength of operation. Calculations indicate an improvement in the element’s overall propagation attenuation by about two orders of magnitude when compared to previous results dealing directly with MQW optical waveguides. Promising element performance characteristics are reported.

ISSN:0003-6951    

DOI:10.1063/1.98897

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

The frequency dispersion of integrated optic interferometers fabricated on different lithium niobate substrate orientations is characterized. Dispersion in the dielectric constants and the electro‐optic coefficients causes most device configurations to have a significantly different electro‐optic response at frequencies above and below the acoustic resonances. Only the configuration that uses ther33electro‐optic coefficient displays a broadband, well behaved frequency response.

ISSN:0003-6951    

DOI:10.1063/1.98898

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Reactive ion etching was used for etching laser facets of GaAs/AlGaAs transverse junction stripe lasers. A new load‐locked reactive ion etching system was developed to dramatically reduce the background partial pressure of O2and H2O in the chamber, substantially reducing the oxidation of AlGaAs and permitting equal rate etching of GaAs and AlGaAs with smooth vertical facets. Etching is performed with a chlorine plasma at a low pressure (0.5 mTorr), and bias voltage (−350 V) at a rate of ∼850 A˚/min. This simple, single‐step dry etching process is suitable for optoelectronic integration and eliminates the requirement of unreliable wet chemical etching or microcleaving techniques. This new system is used to fabricate transverse junction stripe lasers with facet reflectivities of more than 16%. These high quality dry etched facets result in only a 7.5% increase of the threshold current above that of lasers with cleaved facets.

ISSN:0003-6951    

DOI:10.1063/1.98899

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

We report on frequency doubling of the 647.1 nm line from a mode‐locked Kr+laser in a single‐mode fiber with pure Ge‐doped core. The harmonic light at 323.5 nm builds up after about 20 min of laser irradiation at 647.1 nm. Peak powers as low as 600 W were sufficient to prepare the fibers for second harmonic generation.

ISSN:0003-6951    

DOI:10.1063/1.98900

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

We have created and characterized a transmissive diffraction grating that disperses 8 keV x rays. The grating has a period of 7077±70 A˚ and consists of opaque zones of Ta separated by transparent zones of Al. It was fabricated by sputtering alternating layers of Al and Ta onto a glass optical flat and then slicing the coating into a 17‐&mgr;m‐thick slab. We tested the performance of the grating against a theoretical prediction by exposing the grating to 8 keV radiation from a Cu x‐ray source and observing the interference pattern.

ISSN:0003-6951    

DOI:10.1063/1.98901

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

A cavity dumped, synchronously pumped femtosecond dye laser is newly described. The laser has a linear cavity configuration with a controller of group velocity dispersion, resulting in pulses as short as 160–240 fs with a peak power of 55 kW. Utilizing a polarization‐preserving fiber and a pair of Brewster‐angled TeO2prisms, optical pulses as short as 56 fs with a peak power of 188 kW have been realized at a repetition rate of 3.8 MHz.

ISSN:0003-6951    

DOI:10.1063/1.99006

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

In laser‐assisted disordering of AlGaAs heterostructures, the Si impurity is locally incorporated with a scanned laser beam. A subsequent thermal diffusion disorders the crystal layer structure by impurity‐induced disordering. Data are presented indicating that under certain conditions the Si diffusion is anisotropic and proceeds most rapidly along the plane of the active region. The shape of the anisotropic disordering front is well suited to fabricating low‐threshold buried‐heterostructure (BH) lasers. Data describing the characteristics of the first BH lasers fabricated using the anisotropic diffusion are presented. The minimum cw threshold current is 10 mA and the maximum power output is 75 mW.

ISSN:0003-6951    

DOI:10.1063/1.98849

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

The change of the properties of the plasma ball created in the laser blow‐off process is investigated in interaction with residual gas and buffer gas particles during its flight in space. The main process of the interaction is the collision leading to plasma particle loss. The center of mass velocity and the temperature of the ball weakly depend on the buffer gas density because the plasma is mainly collisionless.

ISSN:0003-6951    

DOI:10.1063/1.98850

出版商:AIP    

年代:1987

数据来源: AIP