摘要:

The spectral electroluminescence characteristics of broad‐area (Al)GaAs/In0.23Ga0.77As/(Al)GaAs single quantum well separate confinement heterostructure lasers grown on (111)B GaAs have been studied under forward biased current injection. A room‐temperature threshold current density of 750 A/cm2is measured for a 1000 &mgr;m laser. The subthreshold electroluminescence spectrum blue shifts with increasing current up to the point of lasing threshold. Our measurements reveal that lasing is achieved while there is a strong residual or ‘‘unscreened’’ electric field across the quantum well. Based on these observations we outline how piezoelectric quantum wells can be used to monolithically integrate a quantum well laser with a blue‐shifting electroabsorption modulator. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115662

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We calculate the effects of facet roughness on laser performance of etched‐facet semiconductor diode lasers. Facet roughness can be caused by the finite pixel size, used in photolithographic mask fabrication, or in the facet etching process. We consider various sizes of roughness and show that appreciable effects can result from roughness levels previously considered optically flat. Far‐field shifts and modal coupling caused by facet roughness are also calculated. Results are highly useful for designing lasers with curved or arbitrarily oriented facts such as unstable resonators or beam steering fan laser diodes. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115663

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Optoelectronic feedback is proposed as a suitable method for output stabilization of current modulated laser diodes. Numerical simulations show low jitter operation with significant on/off ratios even beyond the relaxation oscillation frequency. Low frequency components in the output power spectra are efficiently suppressed. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115664

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We report our recent study of ultrafast electro‐optic field sensors for the coherent measurement of freely propagating subpicosecond pulsed electromagnetic waves (THz beams). The sensitivity and bandwidth of these electro‐optic sensors are comparable with the conventional ultrafast photoconductive dipole antennas. The simplicity of the detection geometry and capability of optical parallel processing make these sensors suitable for real‐time 2D subpicosecond far‐infrared imaging. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115665

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

A near‐field optical microscope (NFOM) has been developed that combines the features of a near‐field optical microscope and an atomic force microscope. Improved control over tip‐sample separation has led to improved optical imaging and independent surface topography information. The tip oscillation is normal to the sample plane thereby reducing lateral forces—important for nonperturbative imaging of soft samples. Both topographic images and reflection near‐field optical images are presented which demonstrate the capability of the system. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115666

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We show that the nonlinear index perturbation due to light‐induced photovoltaic space‐charge field in LiNbO3can give rise to self‐phase matching of second harmonic generation. Increase of the conversion efficiency is accompanied by formation of stationary and nonstationary patterns in the spatial structure of the generated second harmonic. The space‐charge field can be induced either by the initially non‐phase‐matched second harmonic or by an external seed. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115667

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Third‐order, one‐dimensional, semiconductor‐air gratings have been designed, fabricated, and evaluated by optical waveguide transmission measurements. Gratings with as little as six unit cells show a clear band edge around 840–850 nm. Owing to our approach of semiconductor‐rich lattices with small airgaps, the diffractive spreading loss is sufficiently small (∼50% in the passband) for meaningful results to be extracted. The measurements indicate that the optical waveguide approach is a good starting point for the study of photonic microstructures and that practical device concepts can be implemented. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115668

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

UV laser induced inonization of silicon oxygen deficient centers (SODC) in silica glasses and germanium oxygen deficient centers (GODC) in germanosilicate glasses has been studied by direct displacement photocurrent measurements. For both SODC and GODC the two‐photon (two‐step) nature of photoionization has been established. The cross sections of transitions from first excited to upper (ionizable) states were estimated as &sgr;12=6×10−18cm2for SODC and (0.5–1.0)×10−19cm2for GODC. The effect of pulse‐to‐pulse degradation of the photocurrent signal caused by the screening effect is applied to estimate the lifetimes and ranges of the free carriers. The conclusion was drawn, that ionized SODC and GODC play the key role for free charge trapping. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115669

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

A symmetric rate model for plasma etching and plasma deposition in fluorocarbon plasmas is proposed. When there is no deposition, the symmetric rate model gives a plasma etch rate. When there is no etching, the model gives a plasma deposition rate. Electron cyclotron resonance and reactive ion etcher etch rates of SiO2in CF4plasma are found to be consistent with the model. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115670

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Thin films made by annealing Cu(500 nm)/Al(7 nm)/SiO2/Si are investigated using Rutherford backscattering and resistivity measurements. Annealing these films in a low pressure of oxygen results in the formation of a thin surface layer of hole‐free aluminum oxide which protects the underlying copper from oxidation. Even when heated in air at 350 °C for 4 h, no growth of copper oxide is detected. These films have a resistivity as low as 2.4 &mgr;&OHgr; cm, comparable to the resistivity of pure copper films (2.1 &mgr;&OHgr; cm) made in the same deposition system. The use of such films for microelectronic metallization is briefly discussed. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115671

出版商:AIP    

年代:1996

数据来源: AIP