摘要:

Several organic materials with a bulky donor group have been developed for second‐order nonlinear optics. Among these materials, 2‐adamantylamino‐5‐nitropyridine (AANP) crystal has the largest second‐order nonlinear optical coefficient. By second‐harmonics measurement at 1.064 &mgr;m, coefficients ofd31andd33were determined to be 80 and 60 pm/V, respectively. Angle‐tuned phase‐matched second‐harmonic generation with a conversion efficiency=2×10−3W−1has been demonstrated using a 1 mm AANP bulk crystal at 1.064 &mgr;m.

ISSN:0003-6951    

DOI:10.1063/1.104829

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

A 20‐element linear array of single transverse mode semiconductor lasers is operated in an external Talbot cavity. A total cw output power of 250 mW in a diffraction‐limited far field and 29% differential efficiency is obtained with a 50% output coupler. By decreasing the output mirror reflectivity to 20%, 900 mW cw in a 1.7 times diffraction‐limited radiation pattern with an increased differential efficiency of 38% is obtained. The low fill factor of the array (1:12) acts as a spatial mode‐selective filter resulting in strong mode discrimination.

ISSN:0003-6951    

DOI:10.1063/1.104830

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

For the first time, resonant parallel photoconductivity due to intraband optical transitions is observed in GaAs/AlGaAs multiquantum wells. The angle of incidence dependence of the detected signals indicates that the photoconductivity process is notdirectlyrelated to intersubband transitions. Indeed, contrary to usual detectors based on intersubband transitions, infrared radiations are detectedatnormalincidencewith responsivity as high as (0.05 A/W). Photoconductivity spectra reproduce roughly the absorption spectra with, however, significant differences in peak positions, indicating that the intersubband transitions are indirectly involved in the detection process. Elements of an explanatory model based on hot‐electron bolometric effects are discussed.

ISSN:0003-6951    

DOI:10.1063/1.104831

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The conversion of linearly polarized synchrotron radiation to circular polarization has been successfully achieved beyond the LiF transmission cutoff in the vacuum ultraviolet by utilizing a triple‐reflection polarizer as a quarter‐wave retarder. The Stokes parameters of the emerging beam were directly measured at 30 eV with a reflection‐type polarimeter as a function of the rotation angle of the ‘‘circular polarizer’’ around the optical axis. The results show that a degree of circular polarization of up to ∼±82% was attained at ∼±25° rotation angles, respectively, between the incidence plane for the polarizer and the horizontal plane. This result is in good agreement with a calculation which took into account the independently measured Stokes parameters of the incoming beam.

ISSN:0003-6951    

DOI:10.1063/1.104832

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

An increase of 70% in the catastrophic optical damage (COD) level of AlGaInP visible laser diodes is achieved by sulfur treatment. From transmission electron microscope and energy dispersive microanalysis, we have confirmed that most of the oxide at the mirror facets is replaced by sulfur after this treatment. It is thought that oxide at the facets introduces surface states which cause the COD, and removal of the oxide by sulfur treatment results in the higher COD level.  

ISSN:0003-6951    

DOI:10.1063/1.104833

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

An experimental study on spontaneous and stimulated emission properties of planar optical microcavities confining an organic dye solution is reported. The lasing threshold in an input‐output curve became indistinct by decreasing the distance between a pair of dielectric reflectors. The coupling ratio of spontaneous emission into a laser mode was as large as 0.2 for a cavity half a wavelength distance. Differences between the spontaneous emission dominant regime and the stimulated emission dominant regime were also examined with emission spectra and emission lifetime measurements.

ISSN:0003-6951    

DOI:10.1063/1.104834

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Thermal treatment of a Mo/Si multilayer stack enhances its reflectivity in the soft x‐ray region. The multilayer x‐ray mirrors are fabricated by electron beam evaporation in ultrahigh vacuum.Insitumeasurement of the reflectivity during the deposition allows thickness control and an observation of changes in quality of the boundaries. By heating the substrates during deposition we obtain a smoothing of the interfaces. This leads to x‐ray mirrors with peak reflectivity around 50% for normal incident radiation of wavelengths between 130 and 140 A˚.

ISSN:0003-6951    

DOI:10.1063/1.104835

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

A microstrip line with a highly conducting cobalt silicide (CoSi2) ground plane buried 7 &mgr;m below the surface of a single‐crystal silicon wafer is presented. This new transmission line shows significantly reduced dispersion up to 100 GHz bandwidth compared to a conventional microstrip line with the ground plane on the back of the substrate, while being able to support active devices in the silicon dielectric. After propagating 5 mm, the rise time (10%–90%) of an electrical pulse increases only from 2.5 to 3.7 ps as opposed to an increase from 2.7 to 11.3 ps on a conventional microstrip line.

ISSN:0003-6951    

DOI:10.1063/1.104836

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

A two‐step double ion‐exchange process is employed to produce dual‐core waveguides in glass. First, potassium ion exchange is carried out at 400 °C. Then, silver ion exchange is performed at 300 °C. The fabricated waveguides have low losses, large single‐mode regions, and more symmetrical profiles than single ion‐exchanged waveguides. Etched gratings are also made in dual‐core waveguides. Very high efficiencies are demonstrated in these waveguides.

ISSN:0003-6951    

DOI:10.1063/1.104837

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We have succeeded in preparing 1.5 &mgr;m wavelength strained‐layer graded‐index separate confinement heterostructure (GRINSCH) InGaAs/InGaAsP single quantum well (SQW) injection lasers by chemical beam epitaxy (CBE). These lasers have extremely low threshold current densityJthof 170 A/cm2, internal quantum efficiency of 83%, and internal waveguide loss of 3.8 cm−1. To the best of our knowledge, these results represent the best values obtained thus far from long‐wavelength InGaAs/InGaAsP quantum well injection lasers grown by any techniques. However, despite the recent rapid reduction inJth, the threshold‐temperature dependence remains poor (T0=45 K) even in these very lowJthGRINSCH SQW lasers.

ISSN:0003-6951    

DOI:10.1063/1.104838

出版商:AIP    

年代:1991

数据来源: AIP