摘要:

Time‐resolved photoluminescence has been employed to study the mechanisms of band‐edge emissions in Mg‐dopedp‐type GaN. Two emission lines at about 290 and 550 meV below the band gap (Eg) have been observed. Their recombination lifetimes, dependencies on excitation intensity, and decay kinetics have demonstrated that the line at 290 meV below Eg is due to the conduction band‐to‐impurity transition involving shallow Mg impurities, while the line at 550 meV below Eg is due to the conduction band‐to‐impurity transition involving doping related deep‐level centers (or complexes). ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116282

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

A 4 cm long Er‐doped Al2O3spiral waveguide amplifier was fabricated on a Si substrate, and integrated with wavelength division multiplexers within a total area of 15 mm2. When pumped with 9 mW 1.48 &mgr;m light from a laser diode, the amplifier shows 2.3 dB net optical gain at 1.53 &mgr;m. The gain threshold was 3 mW. The amplifier was doped with Er by ion implantation to a concentration of 2.7×1020cm−3. The data agree well with calculations based on a model which includes the effects of cooperative upconversion and excited state absorption. For an optimized amplifier, net optical gain of 20 dB is predicted. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116283

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Temporal decay characteristics of dislocation‐related luminescence bands (D1–D4) were explored in strain‐relieved epitaxial SiGe/Si(100). Close similarity of the decay profiles was observed not only between D1 and D2 bands but also between D3 and D4 bands. The decay transients of the D1 and D2 bands at low temperatures are characterized by long decay times, &tgr;≳200 ns, whereas the D3 and D4 bands exhibit even sharper transients with &tgr;<60 ns. Temperature dependence of ‘‘radiative’’ lifetimes implies a free‐to‐bound nature of the D1 and D2 bands, while a bound‐to‐bound character of the luminescence origins for the D3, D4 bands. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116284

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

A phenomenological model describing the temperature dependence of the threshold current of 1.3 &mgr;m gain‐coupled distributed feedback (DFB) lasers with periodically etched strained‐layer quantum wells is presented and compared to experimental results. The model can predict the minimum threshold current as a function of temperature (infiniteT0), which has been observed experimentally. The mechanism for the appearance of this minimum is explained by the decrease of the detuning of the DFB‐mode wavelength from the material gain‐peak wavelength as the temperature increases. The condition for single‐mode operation is also discussed with use of the effective gain of DFB laser structures. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116285

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

An InGaAs/GaAs vertical‐cavity surface‐emitting laser has been fabricated on a (311)B GaAs substrate. Pulsed lasing operation is obtained at room temperature, and continuous‐wave lasing operation is obtained at less than 270 K. From the device, blue laser emission based on second‐harmonic generation is observed. The wavelength of the blue laser emission is 482 nm. At 135 K, its output power is 1 nW under continuous‐wave operation and more than 10 nW under pulsed operation. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116286

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We have investigated the lateral thermal oxidation of AlAs in water vapor in vertical cavity surface emitting laser structures. At low temperatures and short oxidation times, oxide growth was found to be reaction rate limited. Conversely, diffusion across the oxide was the rate controlling mechanism at higher temperatures and longer oxidation times. Lasers are typically processed at intermediate values of temperatures and time. The observed growth can be modeled by rate equations by which the two component growth mechanisms can be separated. Activation energies of 1.6 and 0.8 eV were determined for the reaction rate and diffusion limited mechanisms, respectively. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116287

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Unlike crystals producing sharp peaks under the x‐ray diffraction, disordered materials show slowly varying patterns presenting little structural information. This is due to the fact that only the scattering intensity can be recorded, and the loss of the phase information makes the Fourier inversion of the amplitude impossible. However, when an amorphous sample is placed on a crystal, the x‐ray intensity diffracted by the assembly can produce a hologram which contains the spatial modulation of both density functions. Therefore, with known crystal structure the electron density of the amorphous specimen can be resolved by holographic technique. Moreover, it is found that only the amorphous scattering data are needed, and the Bragg peak(s) can be dropped. This gives the scheme the same noise tolerance as by the ordinary amorphous diffraction. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116288

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

A reverse biased Schottky diode is used to deplete the population in quantum wells and to modulate the intersubband absorption coefficient. This middle infrared electro‐optic modulator works at room temperature. A waveguide geometry is demonstrated, with only six quantum wells. The 14% modulation could easily be enhanced by optimizing the quantum well overlap with the optical guided mode of the waveguide. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116289

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

In terms of the quasiperiodicity of temporal coherenceg(1)(&tgr;) in a multimode gas laser, we present measurements of both spectral line shape function and frequency width of longitudinal mode in a multimode laser. The experimental result shows that the spectral line shape of longitudinal mode is Lorentzian line‐shape function for a freely operated multimode gas laser with inhomogeneous broadening, it is not affected by the drift effect of longitudinal mode frequency. However, the frequency width of longitudinal mode is broadened greatly because of the influence of the drift effect of longitudinal mode frequency. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116290

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Temperature induced changes in thickness and refractive index of thin films of benzocyclobutene (BCB) have been studied with ellipsometry in the temperature range 22–190 °C. The ellipsometric parameters &PSgr; and &Dgr;, which depend on both the thickness and the optical constants of the BCB films, change significantly with temperature with short response times. The temperature sensitivity, resolution, and dynamic range depend on film thickness and wavelength. For a film with thickness 4.73 &mgr;m, a sensitivity of 0.2°/°C with a resolution of 0.25 °C is achieved within a range of 170 °C. Thermal expansion coefficients (TEC) of BCB films with different thicknesses evaluated from spectroscopic ellipsometric measurements are in the range 6.1–6.5×10−5/°C. Based on the findings here, a real‐time detection system for remote optical monitoring of surface temperature variation can be developed. A technique for the determination of TEC of some organic films is also feasible. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116291

出版商:AIP    

年代:1996

数据来源: AIP