摘要:

Iron oxide and tin oxide have been photodeposited in porous Vycor glass and examined before and after consolidation of the glass. Scanning electron microscopy reveals that the iron oxide particles are larger than the tin oxide particles. However, small‐angle x‐ray scattering and Rutherford backscattering show that the glass consolidates about the iron oxide but not about the tin oxide. Photodeposition of tin oxide, which appears to chemically modify the glass surface and to prevent its consolidation, offers a means of producing highly resolved regions of porosity in the otherwise consolidated glass.

ISSN:0003-6951    

DOI:10.1063/1.103740

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The two‐photon absorption (TPA) coefficient has been measured for a single‐mode GaAs/AlGaAs quantum well laser at 0.86 &mgr;m, near the lasing wavelength of 0.83 &mgr;m. Picosecond laser pulses were employed to resolve the ultrafast TPA from long‐lived carrier‐dependent effects. The TPA coefficient was found to be 31±6 cm GW−1, which corresponds to a value of (5.7±1.2)×10−11esu for the imaginary part of the third‐order nonlinear susceptibility. At wavelengths near the quantum well exciton, no strong resonance enhancement of the two‐photon transition was observed, and the coefficient appears to be characteristic of the AlGaAs cladding layers.

ISSN:0003-6951    

DOI:10.1063/1.103741

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We report on the observation of resonant intersubband second‐harmonic generation in asymmetric GaAs/AlGaAs quantum wells using a cw orQ‐switched tunable CO2laser as the pumping source. The dependence of the second‐harmonic intensity with the pump photon wavelength is presented for the first time. A Lorentzian‐like second‐harmonic line shape is found with a maximum at 10.9 &mgr;m and a linewidth of 0.4 &mgr;m (4.1 meV). These results are in good agreement with theoretical predictions. The expected quadratic dependence of the second‐harmonic conversion efficiency with pump intensity is well verified for intensities up to 150 kW/cm2. The calibrated second‐harmonic power reaches 0.13 &mgr;W for a cw pump power of 0.8 W. The value of 7.2×10−7m/V deduced for the second‐order nonlinear susceptibility is about 1900 times greater than that found in bulk GaAs.

ISSN:0003-6951    

DOI:10.1063/1.103742

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Transverse mode characteristics of vertical cavity surface‐emitting (VC‐SE) lasers are described. The mode structure is investigated as a function of the transverse dimension for proton‐implanted gain‐guided VC‐SE lasers. A comparison is made to an air‐post index‐guided structure. The lasing modes and the evolution of the modes with increasing drive current for the VC‐SE lasers are observed to be highly analogous to those of the edge‐emitting lasers. Broad‐area gain‐guided lasers lase in the fundamental TEM00mode near threshold. At higher currents, high‐order modes are successively excited. A 5 &mgr;m square proton‐implanted gain‐guided VC‐SE laser emits a single mode. On the other hand, an air‐post index‐guided SE laser, due to the large index difference between the laser and the cladding, emits multiple transverse modes. Moreover, we show that the gain‐guided VC‐SE lasers exhibit better device characteristics than the air‐post index‐guided lasers.

ISSN:0003-6951    

DOI:10.1063/1.103743

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A new type of chalcone crystal was prepared. Anisotropic indices with wavelength dispersion were measured by the Brewster angle method. The two largest second‐harmonic generation (SHG) tensor components were determined by the wedge method and compared withd11of 2‐methyl‐4‐nitroaniline. Calculated collinear and noncollinear phase‐matched SHG patterns reasonably fit the observed photographs.

ISSN:0003-6951    

DOI:10.1063/1.103744

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A record high power output strained‐layer InGaAs/InP quantum well laser emitting at 1.48 to 1.51 &mgr;m is demonstrated. Maximum cw output as high as 206 mW is obtained from a sample with a cavity length of 890 &mgr;m and a facet reflectivity of ∼5 and 85% for the front and the rear facets, respectively. The laser has a threshold of 30 mA and a slope efficiency as high as 0.4 mW/mA.

ISSN:0003-6951    

DOI:10.1063/1.103722

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Device structure, fabrication method, and experimental results of a GaAs/AlGaAs traveling‐wave directional coupler optical modulator/switch operated at 1.06 &mgr;m wavelength are described for the first time. An extinction ratio of 13.7 dB has been measured at the switching voltage of 10.4 V, and a 3 dB bandwidth of 9.1 GHz has been demonstrated for a device with a waveguide width of 5.5 &mgr;m, waveguide spacing of 3.5 &mgr;m, and length of 8 mm.

ISSN:0003-6951    

DOI:10.1063/1.103723

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

All solid‐state cw passive mode locking of a Ti:sapphire laser is accomplished using a colored glass filter, instead of an organic dye, as a saturable absorber. The tuning range is remarkably wide (785–855 nm), and 2.7 ps pulses are obtained directly from the cavity.

ISSN:0003-6951    

DOI:10.1063/1.103724

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The enhancement of theH2(&ngr;″)vibrational distribution observed in the medium‐density hydrogen discharge of Eenshuistra and co‐workers is investigated theoretically as a function of different excitation processes. The observed fivefold enhancement of the&ngr;″=5population with increasing discharge current is reproduced in the model. Principal excitations generating this enhancement areH+3surface recombination and fast‐electron excitation. Atom‐surface recombination may be a principal contributor near the&ngr;″=1portion of the spectrum.

ISSN:0003-6951    

DOI:10.1063/1.103725

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Two bubbles are simultaneously generated in water by focusing aQ‐switched ruby laser. The dynamic behavior of the induced bubbles is investigated by means of high‐speed photography. Consequently it is found that the bubble–bubble interaction is significantly influenced not only by the relative size of bubbles but also by the mutual distance between them. When two bubbles are axisymmetrically produced one behind the other near a rigid wall, we can observe a very interesting phenomenon, bubble splitting followed by bubble pinching.

ISSN:0003-6951    

DOI:10.1063/1.103726

出版商:AIP    

年代:1990

数据来源: AIP