摘要:

We observe that stimulated emission from inhomogeneously pumped quantum well laser diodes is shifted down in energy compared with the subband transition energy. Measured spontaneous emission spectra show that this stimulated emission is due to band‐to‐band transitions shifted by renormalization at high injected carrier densities, and we suggest that this same mechanism explains reported observations of stimulated emission from inhomogeneously photopumped structures which previously have been interpreted as evidence for longitudinal optic (LO) phonon participation. We show that LO phonon participation cannot account for the photon energy of stimulated emission from conventional homogeneously pumped quantum well laser diodes.

ISSN:0003-6951    

DOI:10.1063/1.101745

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Thin films of VOxFywere made by rf magnetron sputtering of V in Ar+O2+CF4. They were analyzed by Rutherford backscattering spectrometry and transmission electron microscopy. Optical and electrical properties changed within narrow temperature ranges. These results resemble those of thermochromic VO2, although VOxFyhas significantly enhanced transmittance, lowered conductance, and marginally depressed switching temperature.

ISSN:0003-6951    

DOI:10.1063/1.102388

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Tunable subpicosecond infrared pulses have been generated in the 1.4–1.6 &mgr;m region by mixing a 1.064 &mgr;m Nd:YAG laser pulse and a visible subpicosecond pulse from a cavity dumped, synchronously pumped dye laser. Pulses as short as 94 fs with a peak power of 8.4 kW have been obtained with a KTP crystal at a rate of 3.8 MHz.

ISSN:0003-6951    

DOI:10.1063/1.101759

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

A resonant phase‐locked array of antiguides is demonstrated for the first time. A 10/11 element AlGaAs/GaAs antiguided array is grown by two‐step metalorganic chemical vapor deposition. Longitudinally, the structure consists of two noncollinear sets of antiguides separated by a half‐Talbot distance, an ensemble that acts as a spatial filter. Out‐of‐phase‐mode operation is suppressed both by this diffractive‐type spatial filter and by large interelement loss. Resonant in‐phase‐mode operation is a result of the interelement spacing corresponding to one leaky‐wave half wavelength in the lateral direction. Near the in‐phase‐mode resonance, array modes adjacent to the in‐phase‐mode are discriminated against because they have large radiation losses in the antiguided structure and significant edge diffraction losses in the spatial filter. Stable, diffraction‐limited in‐phase‐mode beam patterns are achieved to 10 times threshold and 450 mW output power.

ISSN:0003-6951    

DOI:10.1063/1.101741

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Picosecond pulses are observed to exhibit large frequency shifts (∼50 GHz) and spectral distortion on propagation through semiconductor laser optical amplifiers. The spectral changes are shown to result from self‐phase modulation occurring due to the carrier‐induced index changes that invariably accompany gain saturation. An analytic model for pulse amplification is presented by including the self‐phase modulation effects. Its predictions are in good agreement with the experimental results.

ISSN:0003-6951    

DOI:10.1063/1.101742

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Lattice‐matched double‐heterostructure (DH) PbEuSeTe lasers were grown by molecular beam epitaxy (MBE) on (100) oriented PbTe substrates. Grooved mesa structures with 17–25 &mgr;m wide stripes and 0.75 &mgr;m thick Pb1−xEuxSeyTe1−yactive layers with 0≤x≤0.031 were fabricated. DH diode lasers with a PbTe active layer reached a maximum cw operation temperature of 175 K which equals the highest operation temperature achieved so far by a side optical cavity (SOC) single quantum well (SQW) PbTe/PbEuSeTe laser. The threshold current density of 3.9 A/cm2measured for this laser at 15 K is, to our knowledge, the lowest ever published for lead salt lasers. Comparison of MBE‐grown DH lasers which utilize the lattice‐matched PbTe/PbEuSeTe system to those utilizing the nonlattice‐matched PbSe/PbEuSe system shows higher operation temperatures and by far lower threshold currents for the lattice‐matched system.

ISSN:0003-6951    

DOI:10.1063/1.101743

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

An external‐cavity semiconductor laser employing a birefringent electro‐optic modulator for wavelength tuning is described. Wide‐band tuning over 70 A˚ in a single frequency to residual diode modes and narrow‐band tuning over 0.42 A˚ to many longitudinal modes of the external cavity is demonstrated using different modulator configurations. Threshold current and quantum efficiency are nearly as good as that of the solitary laser diode.

ISSN:0003-6951    

DOI:10.1063/1.101744

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

We have studied room‐temperature optical gating of ∼5 ps pulses in GaAs/AlAs microresonators with diameters ranging from <0.5 &mgr;m to 1.5 &mgr;m by using a high‐refractive‐index lens system having a numerical aperture of 1.3. The larger devices exhibited well‐defined transverse modes, which caused decreased modulation of the probe beam. Waveguide dispersion, present in all the devices, showed fair agreement with calculations. The smallest diameter devices (<0.5 &mgr;m) show high modulation, fully recover in <30 ps, and have their peak transmission wavelengths shifted by >500 A˚ compared to a large ∼10 &mgr;m nearby region.

ISSN:0003-6951    

DOI:10.1063/1.101746

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Switching in less than 1 ns of an optical signal at 632 nm is demonstrated in a 1 m optical fiber Sagnac interferometer. Full signal modulation was obtained with a pump power of 24 W at a wavelength of 532 nm.

ISSN:0003-6951    

DOI:10.1063/1.101737

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Structure mode frequency spreads are shown to have a rather different influence on beam breakup growths than betatron frequency spreads. The present analytic and numerical studies show that a finite spread in the breakup mode frequency leads to an algebraic decay of the beam breakup instabilities even if the quality factorQ→∞. Effects of stagger tuning are examined.

ISSN:0003-6951    

DOI:10.1063/1.101738

出版商:AIP    

年代:1989

数据来源: AIP