摘要:

This letter describes the monolithic integration of a laser diode and an optical waveguide modulator that have the same GaAs/AlGaAs quantum well double heterostructure grown on the same substrate. The intensity of the light emitted from the laser diode is modulated by the modulator, utilizing the effect of an electric field on exciton absorption. The absorption loss coefficient of the modulator waveguide with no applied voltage was estimated to be 60 cm−1. This value is much smaller than the previously reported corresponding value of a veguide having a conventional GaAs double heterostructure. The modulation depth achieved was 7 dB for a driving voltage of 2.3 V; the cut‐off modulation frequency was 0.88 GHz. A prospect for improving these characteristics is also presented.

ISSN:0003-6951    

DOI:10.1063/1.96776

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Ridge waveguide AlGaAs/GaAs distributed feedback lasers were fabricated by a two‐step molecular beam epitaxial growth technique. A threshold current as low as 42 mA, which is the lowest ever reported, was obtained under a continuous wave condition at room temperature. Stable single longitudinal mode oscillation was observed in the temperature range from −20 to 30 °C without any suppression of the Fabry–Perot mode.

ISSN:0003-6951    

DOI:10.1063/1.96758

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

We describe the fabrication of closely spaced arrays of buried heterostructure semiconductor lasers by the process of silicon impurity induced disordering. These devices have the low threshold currents which are associated with buried heterostructure lasers, as well as high overall device efficiency. The device we have analyzed for this letter exhibits a threshold current of 53 mA, differential quantum efficiency of 62%, and a total power conversion efficiency of 43% when operating at a power output level of 250 mW. These numbers indicate that this technology is quite promising for the fabrication of high power semiconductor laser arrays.

ISSN:0003-6951    

DOI:10.1063/1.96769

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The electro‐optical properties of a thin layer of nematic liquid crystal, sandwiched between two side‐polished single‐mode optical fibers and flanked by electrodes, are investigated by documenting the response of the resulting fiber coupler to electric fields of different frequencies and amplitudes. It is found that similar coupling states (corresponding to similar states of the liquid crystal) are created at every driving frequency if the correct voltage level (above a threshold dependent on the coupling state) is selected. The presence of certain resonance peaks in the frequency response of the liquid crystal (to our knowledge not before observed) is explained phenomenologically in terms of orientational standing‐wave patterns between the electrodes.

ISSN:0003-6951    

DOI:10.1063/1.96772

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Single mode planar and channel waveguides have been produced in Sr0.6Ba0.4Nb2O6(tungsten bronze structure) by sulfur diffusion in a sealed ampule, followed by oxidation in an open tube. Losses in channel waveguides were ∼15–20 dB/cm for TM polarization and ∼27–32 dB/cm for the TE polarization inz‐cut substrates. Electro‐optic modulation was observed after poling of the substrate. The experimentally determined value of the effective electro‐optic coefficient was slightly greater than reported earlier for bulk samples of SBN:60, and about 15 times greater than for LiNbO3. Based on measurements with the S35radioisotope, the average atomic sulfur concentration was estimated to be about 4×1017/cm3in the region extending from the surface to a depth of 2.5 &mgr;m, and a significant background concentration (∼5×1016/cm3) was present to depths in excess of 20 &mgr;m.

ISSN:0003-6951    

DOI:10.1063/1.96773

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

A self‐consistent model of phased‐array diode lasers, which takes into account the interaction of the carrier and the field, is presented with numerical simulations on both ideal dielectric coupled waveguides and active phased arrays. While essential agreement between the results of this model and those of coupled mode analysis is obtained for passive waveguides, important differences are found for active arrays. Our results show the development of patterns for the various array modes in the active regions.

ISSN:0003-6951    

DOI:10.1063/1.96774

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Symmetrical buried waveguides with fiberlike refractive index profiles using Ag+‐Na+exchange have been realized in soda‐lime‐silicate glass substrates. A simple scanning electron microscope technique to determine the silver ion (refractive index) profile is also reported.

ISSN:0003-6951    

DOI:10.1063/1.96775

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

We present the first measurement of a tokamak plasma internal magnetic field based on the analysis of polarization of Zeeman components of a magnetic dipole transition in heavy impurity ion. The circular polarization of the Ti XVII 3834 A˚ line is studied. The values of the component of the toroidal magnetic field in the direction of observation are measured for several observation angles and good agreement with expected values is found. The result indicates that the method may be useful for measuring the local magnetic field and in particular, the poloidal component of the field, in a tokamak.

ISSN:0003-6951    

DOI:10.1063/1.96777

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

We present a novel and simple method to determine the average composition of multilayers and superlattices by measuring the x‐ray refractive index. Since these modulated structures exhibit Bragg reflections at small angles, by using a triple axis x‐ray spectrometer we have accurately determined the peak shifts due to refraction in GaAs/AlxGa1−xAs and Nb/Ta superlattices. Knowledge of the refractive index provides the average fractional composition of the periodic structure since the refractive index is a superposition of the refractive indices of the atomic constituents. We also present a critical discussion of the method and compare the values of the average fractional composition obtained in this manner to the values obtained from the lattice parameter change in the GaAs/AlxGa1−xAs superlattices due to the Al.

ISSN:0003-6951    

DOI:10.1063/1.96749

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Silicon oxynitride films, made by reacting porous, sol‐gel derived silicon dioxide with ammonia, were oxidized in dry O2between 800 and 1000 °C. Film oxidation was characterized by ellipsometry and secondary ion mass spectrometry. Increasing the nitrogen content of the film increased oxidation resistance of the film.

ISSN:0003-6951    

DOI:10.1063/1.96750

出版商:AIP    

年代:1986

数据来源: AIP