摘要:

An InAlAs native oxide is used to replace thep-nreverse-biased junction in a conventional buried heterostructure InP-based laser. This technique reduces the number of regrowth steps and eliminates leakage current under high-temperature operation. The InAlAs native oxide buried heterostructure (NOBH) laser with strain-compensated InGaAsP/InP multiple quantum well active layers has a threshold current of 5.6 mA, a slope efficiency of 0.23 mW/mA, and a linear power up to 22.5 mW with a HR-coated facet. It exhibits single transverse mode with lasing wavelength at 1.532 &mgr;m. A characteristic temperature(T0)of 50 K is obtained from the NOBH laser with a nonoptimized oxide layer width. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122899

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We report successful deposition of epitaxial nonlinearKTa0.52Nb0.48O3(KTN) films on (100) GaAs substrates. A buffer layer scheme consisting of epitaxial MgO andSrTiO3buffer layers and aSi3Ni4encapsulation of the substrate was developed to alleviate chemical and structural incompatibilities between the GaAs substrate and KTN film at the growth temperature (∼750 °C). The structure, composition, and preliminary optical properties of the KTN films were evaluated by four-circle x-ray diffraction, Rutherford backscattering spectrometry, and prism coupled optical waveguide mode measurements, respectively. We observed sharp and distinguishable transverse electric and transverse magnetic propagating modes in the KTN films, and measured the refractive index(n0)of the film at 488 nm to be 2.275 which is close to the bulk value of 2.35, all of which indicates a high structural and optical film quality. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122900

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We show that for continuous wave second-harmonic generation using quasiphase matching in periodically segmented waveguides, thermal loading caused by the fundamental and the generated beams degrades the quasiphase matching condition which corrupts the spectral quality of the second-harmonic field. We also show that a carefully designed external temperature gradient leads to an enhancement of the conversion efficiency and control of the spectral line shape of the output field. Compared to earlier work, our simple scheme yields an enhancement of the second-harmonic conversion efficiency by a factor of 2–4 depending on the input fundamental power. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122901

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Results on molecular beam epitaxy-grown microcavity light-emitting diodes with InGaAs/GaAs quantum wells and a hybrid top mirror are presented. An external quantum efficiency of 14.8&percent; is achieved for a 400 &mgr;m diam light-emitting diode. The strong influence of the spectral overlap between the spontaneous emission spectrum and the cavity resonance mode on the radiation pattern is shown. The angular emission profile is compared with model predictions for different detunings, and a very good agreement is obtained when the asymmetric spectral broadening of the intrinsic spontaneous emission is taken into account. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122902

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We report the effect of metal-island size variation in nanoparticle-enhanced photodetectors. Nanoparticle size was controlled by varying the deposition and annealing conditions used to produce the metal-island films. Increasing the size of silver-island particles fabricated onto 165 nm thick silicon-on-insulator (SOI) photodetectors resulted in a dramatic increase in the observed photocurrent. A nearly factor-of-20 photocurrent enhancement was observed for light of wavelength 800 nm, a significant improvement over previously reported results. The improvement is linked to two physical effects: the increased scattering efficiency of the larger nanoparticles and a qualitative change in the resonance characteristics of the metal-island film due to radiative coupling to the SOI waveguide modes. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122903

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We have observed the saturation of intraband absorption in InAs/GaAs self-assembled quantum dots. The investigatedn-doped self-assembled quantum dots exhibit an intraband absorption within the conduction band, which is peaked at an 8 &mgr;m wavelength. The saturation of the intraband absorption is achieved with an infrared pump delivered by a pulsed free-electron laser. The saturation of the transition is observed for an intensity around ≈0.6 MW&hthinsp;cm−2. The electron relaxation time under intraband excitation is measured by time-resolved pump–probe experiments. An electron relaxation timeT1≈3&hthinsp;psis reported. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122904

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

An all-optical sampling technique that allows the simultaneous measurement of optical pulse intensities and wavelengths with a temporal resolution of about 1 ps is introduced. Using four-wave mixing (FWM) in a semiconductor optical amplifier, the optical signal under test is cross correlated with nearly transform-limited 1.4 ps optical sampling pulses. While the intensity of the generated FWM signal is used to determine the temporal shape of the signal intensity, the wavelength of the FWM signal yields time-resolved information about the signal wavelength (i.e., the frequency chirp). Using this technique, the correlation of intensity and wavelength dynamics of pulses generated by a self-Q-switched distributed-feedback laser is determined directly. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122905

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A general technique has been demonstrated at microwave and submillimeter-wave frequencies for photoconductive sampling in the frequency domain using photomixers and continuous-wave laser diodes. A microwave version in which two photomixers were coupled by a transmission line was developed to quantitatively test the concept from 0.05 to 26.5 GHz. A quasioptical version using antenna-coupled photomixers was demonstrated from 25 GHz to 2 THz. Such a system can outperform systems based on time-domain photoconductive sampling in frequency resolution, spectral brightness, system size, and cost.

ISSN:0003-6951    

DOI:10.1063/1.122906

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The products of laser ablation of graphite in a nitrogen atmosphere have been studied by transmission electron microscopy and electron energy-loss spectroscopy. Using nickel and cobalt as catalyst, single-wall carbon nanotubes can be produced with a yield similar to that obtained in an inert gas. Nitrogen has not been found in the nanotubes and crystallized fullerenes although it has been detected in amorphous carbon. A growth model has been proposed to explain the experimental results. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122907

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The realization of the first noncascaded intersubband injection lasers based on a single optical transition is reported. The unipolar lasers are based on an active region consisting of three InGaAs quantum wells closely coupled by thin AlInAs barriers. The lasers emit at&lgr;≈7.7&hthinsp;&mgr;mwavelength and operate in pulsed mode up to 110 K. Peak power levels of 20 mW at 10 K and 4 mW at 110 K are obtained. The low-temperature threshold current density is 25.6 kA&hthinsp;cm−2in good agreement with calculations. Several advantages arise from this novel type of intersubband laser. First, only few layers are necessary to build the active region, simplifying sample preparation. Second, low operating voltages can be achieved, which is essential for many applications. Finally, the noncascaded intersubband laser allows studying fundamental properties of quantum cascade lasers without possible artifacts introduced by the sequential stacking of many active regions. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122908

出版商:AIP    

年代:1998

数据来源: AIP