摘要:

Impurity‐induced disordering of GaAs/AlGaAs multiple quantum well waveguide structures has been carried out using the neutral impurities boron and fluorine, introduced by ion implantation and followed by thermal annealing. Substantial blue shifts (up to 100 meV) in the absorption edge have been obtained and, for similar conditions, fluorine‐induced disordering produces larger shifts than boron‐induced disordering. Optical transmission measurements performed in slab and rib waveguides indicate that the additional contribution to the absorption coefficient associated with boron disordering is 15 dB cm−1and with fluorine disordering is only 6 dB cm−1.

ISSN:0003-6951    

DOI:10.1063/1.101597

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Single lateral 180° phase mode operation is realized at a light output of up to 90 mW under pulsed operation using uncoated AlGaAs phased array lasers. Phased array lasers consist of six elements. Each element has a self‐aligned structure, with an interface layer of low AlAs mole fraction, and is fabricated by a two‐step metalorganic chemical vapor deposition method, together with dry etching. Spectrally resolved, near‐field measurements show that the phased array laser oscillates in a completely single lateral mode under pulsed operation. Measurements also show that a slight broadening of the far‐field lobes under continuous wave operation is caused by generation of multiple lateral modes.

ISSN:0003-6951    

DOI:10.1063/1.101598

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

We report on low threshold current strained InGaAs/AlGaAs single quantum well lasers grown by molecular beam epitaxy. Broad‐area threshold current densities of 114 A/cm2at 990 nm were measured for 1540‐&mgr;m‐long lasers. Threshold currents of 2.4 mA at 950 nm were obtained for an uncoated buried‐heterostructure device with a 2‐&mgr;m‐wide stripe and 425‐&mgr;m‐long cavity. With reflective coatings the best device showed 0.9 mA threshold current (L=225 &mgr;m). Preliminary modulation measurements show bandwidths up to 5.5 GHz limited by the detector response.

ISSN:0003-6951    

DOI:10.1063/1.101599

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

We present a theoretical prediction of a new class of unstable orbits of the equilibrium electrons in free‐electron lasers, which is entirely associated with the radial self‐electric field and azimuthal self‐magnetic field. It is also pointed out that these self‐fields may deteriorate the beam quality and thus decrease the growth rate of the free‐electron laser mode.

ISSN:0003-6951    

DOI:10.1063/1.101600

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

The light emission characteristic of a GaAs/AlGaAs single quantum well laser with an intracavity monolithic loss modulator has been investigated. Discrete, widely separated, wavelength switching from the first (875 nm) to the second (842 nm) subband is achieved by changing the applied modulator bias. In addition, we show that 2 mW of lasing light power may be modulated with a change in current of 250 &mgr;A and a voltage change of 1 V.

ISSN:0003-6951    

DOI:10.1063/1.101601

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

The effects on a CH4‐H2discharge plasma due to the addition of water vapor to the feed gas have been studied. Surprisingly it is found that the concentrations of most positive and negative hydrocarbon ions in the discharge are substantially increased. Possible mechanisms for the increase are presented.

ISSN:0003-6951    

DOI:10.1063/1.101602

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

We show that nearly all of the infrared absorption associated withsp2coordination in diamond‐like carbon deposited from benzene plasma is due to pendant (mono‐substituted) benzene. Because these pendant groups have little effect on the optical and mechanical properties of the film, which are determined by the connected covalent network to which they attach, they obscure the connection between those properties and thesp3/sp2bonding ratio in diamond‐like carbon.

ISSN:0003-6951    

DOI:10.1063/1.101603

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Subjecting natural diamond single crystals to the action of atomic hydrogen in a hydrogen plasma is shown to result in the passivation of interband states in the crystal resulting in a marked reduction in the resistivity to about 105&OHgr; cm from the expected high resistivity of∼1016&OHgr; cm. When the hydrogenated crystals are heat treated in a neutral ambient, the hydrogen can be expelled from the crystals, restoring the high resistivity. The behavior of natural diamond crystals, with respect to the effects of hydrogen, is shown to be similar to the behavior of diamond thin films synthesized by plasma‐enhanced chemical vapor deposition techniques.

ISSN:0003-6951    

DOI:10.1063/1.101604

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

We have developed a novel technique for determining interfacial roughness from plan‐view transmission electron diffraction. Certain bulk forbidden Bragg reflections can occur due to crystal termination at surfaces and are very sensitive to steps on crystal boundaries. We demonstrate the technique in the study of Si/SiO2interfaces and observe that interfaces appear to be significantly flatter than previously found, especially after post‐oxidation annealing. The technique is simply quantified and is more reliable than those which require stripping of the oxide to expose the interface.

ISSN:0003-6951    

DOI:10.1063/1.102280

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

We have implanted boron ions into insulating natural diamonds which were predamaged by carbon ion implantation in order to enhance the doping efficiency. All implantations were performed at liquid‐nitrogen temperature. Subsequent rapid thermal annealing at 1100 °C produced strong new optical absorption bands near 1060 cm−1, and a sharp absorption at 2962 cm−1(0.37 eV) which is close to that attributed to substitutional boron in type IIB diamond. We obtained resistivity of the order of 100 &OHgr; cm and carrier activation energy of 0.1 eV for a sample implanted with 2×1015C and 3×1014B per cm2, indicating a high substitutional fraction of boron atoms.

ISSN:0003-6951    

DOI:10.1063/1.101605

出版商:AIP    

年代:1989

数据来源: AIP