摘要:

Large nonresonant third‐order hyperpolarizabilities, &ggr;1111, for solutions of three organic charge‐transfer complexes in tetrahydrofuran have been measured. The values obtained for nonresonant &ggr;1111are 5.8×10−32esu for Perylene/tetracyanoethylene, 1.2×10−32esu for Pyrene/tetracyanoethylene, and 7.2×10−33esu for Naphthanthracene/tetracyanoethylene. The corresponding values of the third‐order susceptibility &khgr;(3)1111for the solid state are estimated to be 1.0×10−9esu, 2.3×10−10esu, and 1.3×10−10esu, respectively.

ISSN:0003-6951    

DOI:10.1063/1.105465

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We report the first example of second‐harmonic generation in a quartz ion‐implanted waveguide. The example operated with low‐power pumping near 783 nm. The harmonic production near 392 nm follows a square law dependence. A detailed fit of the pumping efficiency with wavelength suggests there is a phase match throughout the length (zpropagating) of the sample. The mode match used was between TE0of the fundamental and TE2of the harmonic (ordinary index).

ISSN:0003-6951    

DOI:10.1063/1.105466

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

A high‐efficiency operation of a vacuum ultraviolet (VUV) incoherent light source of a F2excimer lamp [157 nm:F2(D’)‐F2(A’)] excited by a pulsed microwave discharge has theoretically been studied. Despite the low‐pressure (300 Torr) operation, an intrinsic efficiency of 10.6% and a F2(D’) formation efficiency of 17.4% were found to be obtainable at an optimum F2concentration (0.5%) using He/F2mixtures. The F2(D’) state is mainly produced by energy transfer reaction from F*. Using a 300 Torr mixture of He/F2=99.5/0.5(%), a photon extraction efficiency of 60.9% is achievable with a low energy loss (39.1%) by collisional quenching. The corresponding optical output of 50.0 &mgr;J/cm3is achievable at an excitation rate of 100 W/cm3and an excitation pulse width of 9.0 &mgr;s. Since it can be operated at high repetition frequency of up to 55 kHz using conventional devices, an average output power of 2.75 W/cm3is achievable.

ISSN:0003-6951    

DOI:10.1063/1.105467

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Laser intensity dependence of transmission and the light‐modulation effect of boron‐doped hydrogenated amorphous silicon (a‐Si:H) were investigated with 780 nm laser diodes. Negative intensity dependence, which causes the transmission to decrease as the laser intensity is increased, was observed for B‐doped, but not for undopeda‐Si:H. Moreover, a negative light‐modulation effect was discovered where the constant signal light decreases with increasing control light. To explain these phenomena, a double‐absorption model, which has two absorption processes from a level associated with the impurity and from a valence band, was considered.

ISSN:0003-6951    

DOI:10.1063/1.105440

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

In semiconductor superlattices lacking the reflection symmetry, transient internal polarization fields have previously been reported. We show that a modified structure can generate a steady‐state photovoltage. We then propose a new class of photovoltaic transistors in which this voltage directly controls the conductivity of the transistor channel.  

ISSN:0003-6951    

DOI:10.1063/1.105441

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We have measured the soft x‐ray efficiencies of a siliconp‐i‐nphotodiode and a La2O2S:Tm phosphor over a broad energy range. We have also measured the inelastic electron scattering spectra of the constituent materials and obtained values of optical absorption coefficients versus energy. The energy dependence of the efficiencies is well explained by a model based on surface recombination of electron hole pairs, and the quality of data which can now be obtained from synchrotrons makes possible quantitative fits from which we obtain diffusion length, surface recombination velocity, and bulk quantum efficiency.

ISSN:0003-6951    

DOI:10.1063/1.105442

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The noise characteristics of vertical‐cavity surface‐emitting (VCSE) lasers are studied by using the Langevin rate equations modified suitably to include the enhanced spontaneous emission occurring in such microcavity lasers. The intensity and frequency noise spectra show the effects induced by suppression of relaxation oscillations. However, such a suppression depends on the output power as well as on transverse dimensions of the VCSE laser. The laser linewidth increases considerably as a result of enhanced spontaneous emission.

ISSN:0003-6951    

DOI:10.1063/1.105443

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Single‐heterostructure light‐emitting diodes (LEDs) consisting of a wide band‐gapN‐Ga0.51In0.49P emitter and a heavily carbon‐dopedp‐GaAs active layer have been grown by metalorganic molecular beam epitaxy. Trimethygallium has been utilized to dope the GaAs active layer for a hole concentration of 1.5×1020cm−3in order to reduce the radiative lifetime of minority carriers in GaAs. The cw electroluminescent spectra of these LEDs indicate that the injection efficiency of the Ga0.51In0.49P/GaAs heterojunction is not degraded by carbon redistribution, even in the absence of an undoped spacer layer between the GaAs active layer and the Ga0.51In0.49P emitter layer. The transient optical response of the LEDs determines an optical 3 dB bandwidth in the range of 0.6–2.0 GHz. The external brightness of the carbon‐doped LEDs is shown to be approximately a factor of 20 lower than that of double‐heterostructure LEDs containing active layers more moderately doped with Be at 2×1018cm−3.

ISSN:0003-6951    

DOI:10.1063/1.105444

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Low‐threshold and high‐output power of the first InGaAsP/InP graded index strained multiple quantum well lasers emitting near 1.3 &mgr;m wavelength is reported. A continuous wave threshold current of 10 mA and a quantum efficiency of 60% with maximum output power of 100 mW/facet is observed in uncoated lasers having compressively strained InGaAsP quantum wells. With high reflectivity on both facets, a reduced threshold current as low as 3.5 mA is observed. Highest output power of 250 mW was observed in lasers with antireflection‐high reflection coating configuration operating at 10 °C. The improved performance of the lasers is attributed to both the reduced internal absorption loss (6 cm−1) and the suppressed nonradiative recombination in the structure.

ISSN:0003-6951    

DOI:10.1063/1.105445

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Results from two 4 MV, 100 kA coaxial magnetically insulated transmission line virtual cathode oscillator experiments are presented. In both experiments, two distinct microwave pulses with vastly different frequencies were generated during the beam current pulse. The first, lower frequency pulse was found to be produced by an electron reflexing process, while the second, higher frequency pulse was due to the virtual cathode oscillation mechanism.

ISSN:0003-6951    

DOI:10.1063/1.105446

出版商:AIP    

年代:1991

数据来源: AIP