摘要:

An experimental study of diffraction gratings reactive ion etched in germanium is performed. Gratings are designed for the 10.6 &mgr;m infrared CO2laser. Different etchants have been compared to pattern 3‐&mgr;m‐deep grooves in the germanium layers evaporated on a GaAs substrate. The experimental diffraction efficiency (maximum 30%) of the prototype gratings are in good accordance with the theoretical predictions. The U‐shaped grooves have still to be further optimized. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117249

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We report photoluminescence (PL) spectra related to a two‐dimensional electron gas confined at a GaN/AlGaN heterointerface. The recombination between electrons confined in the bottom of the interface potential and photoexcited holes causes a broad PL emission about 50 meV below the GaN exciton emissions. A second emission, attributed to the recombination of electrons in the first excited level at the interface, is also observed close to the excitonic band gap in GaN. The data agree with a self‐consistent calculation of the energy levels and electron concentration at the interface. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117250

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Modal noise and speckle visibility in Gb/s multimode fiber interconnect systems depends on a complex interplay of carrier dynamics, spontaneous emission factor, gain compression, and device dimensions. These competing factors allow scaled low‐power microlasers with optimized design and operating conditions to exhibit modal noise comparable to large incoherent multimode devices. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117251

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We show that two different types of photoquenching effect take place under low temperature illumination of lightlyn‐type bulk GaAs. Both phenomena result in an increase in positron trapping at vacancies. The first associated with a decrease in EL2 absorption, is produced with light of 1.1 &mgr;m wavelength and recovers near 100 K. While little photoquenching related to EL2 is observed after illumination close to the band edge (0.83 &mgr;m), persistent increases in Hall voltage and positron lifetime accompanied by a decrease in near band‐edge absorption are observed. These latter phenomena recover at 50 K. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117252

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Measurements in a semiconductor microcavity reveal the coupling between light‐ and heavy‐hole excitons that is mediated by the electromagnetic vacuum. Three polariton modes constructed from superpositions of heavy‐hole excitons, light‐hole excitons, and photons are observed. The experimental results are in good agreement with the theory of three‐coupled bosonic modes, each coupled to an independent reservoir. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117253

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We investigate experimentally the form birefringence due to photoinduced one‐ and two‐dimensional volume index gratings in DuPont photopolymers. Experimental results on the dispersion of the form birefringence versus the illumination wavelength and the grating period for one‐dimensional gratings are presented. We also investigate the form birefringence due to two‐dimensional volume gratings. Positive form birefringence and biaxial form birefringence can be obtained by recording two volume gratings with different grating wave vectors. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117254

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We present results of near field scanning optical microscopy measurements performed on single mode AlGaAs ridge channel waveguides. The optical intensity distribution just above the surface of the waveguide structure has been measured by scanning a tapered, aluminum‐coated, fiber probe transverse to the waveguide propagation direction. Experimental results are compared with model calculations performed using both the effective index and beam propagation methods. An accurate description of submicron features in the intensity profile near the ridge edges, as well as the magnitude of the field outside the channel, requires the use of the beam propagation method. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117255

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Broadband quarter‐wavelength Bragg reflectors that consist of periodic stacks of fluorides (CaF2–BaF2–CaF2) and GaAs, centered at 1.4 &mgr;m, were grown by molecular beam epitaxy. Despite a total fluoride thickness as high as 720 nm, crack‐free surface morphology was obtained. In this letter, we report a crack‐free standard quarter‐wavelength III–V semiconductor‐fluoride Bragg reflector. With only three stacks, the bandwidth with reflectance above 95% is about 650 nm (1.15–1.80 &mgr;m), while, near the center wavelength, the reflectivity is as high as 99%. Both important wavelengths of 1.3 and 1.55 &mgr;m for optical communication are included in the very wide high reflectance plateau. These mirrors are expected to have wide applications for optical and optoelectronic devices. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117256

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Ring and stripe oxide‐confined vertical‐cavity surface‐emitting lasers are studied. Interesting coupling effects are observed due to the nonzero propagation velocity of the optical mode in the plane of the cavity. The stripe geometries appear interesting due to the very low threshold and provide a convenient means for increasing the aperture size while maintaining uniform current pumping. The ring laser provides a means of obtaining well defined multiple spots in the far field. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117257

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Transient photoconductivity in quantum well infrared photodetectors (QWIPs) is studied using numerical modeling. Transient photocurrent in QWIPs illuminated by steplike infrared radiation consists of two components. A fast component, representing the primary photocurrent, is determined by the processes of the carrier capture to the QWs and transit through the QW structure. Its amplitude can be lower than the steady‐state photocurrent due to the sweep‐out of the photoexcited carriers. A slow component, comprising the multiplied photocurrent, is governed by the recharging of the QWs. The QWIPs can exhibit high photocurrent gain only at frequencies of harmonic infrared radiation lower than the inverse characteristic time of establishing equilibrium at the injecting contact. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117258

出版商:AIP    

年代:1996

数据来源: AIP