摘要:

We describe integration of lasers and optical amplifiers at 1.3 &mgr;m wavelength. The effects of the residual mirror reflectivity at the amplifier front facet are discussed. Using photonic integration techniques very high coupling efficiency of light from the laser to the amplifier sections was observed, with current transfer efficiency (ratio of photocurrent to drive current) as high as 33%. The output light current characteristics of the laser have a slope efficiency higher than 2 mW/mA. This device may be used for digital modulation with very low rf power drive requirements. Modulation at 2 Gbit/s has been demonstrated.  

ISSN:0003-6951    

DOI:10.1063/1.103440

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

UV‐induced enhancement of the subgap optical absorption has been observed in thin films of chemically vapor deposited silicon nitride. The threshold for this process is ∼4 eV. Visible light bleaches out much of the enhanced absorption and 200–400 °C thermal anneals remove the rest, leaving the optical properties of the nitride in the ‘‘as‐grown’’ state. The characteristics of this creation and bleaching process suggest that UV light ‘‘optically dethermalizes’’ the distribution of carriers in localized band tail states. Correlation of our data with recent electron spin resonance results suggests that many of the trapped carriers may be singly occupied silicon dangling bonds.

ISSN:0003-6951    

DOI:10.1063/1.104089

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The nonlinear refractive indexn2is reported for quantum‐confined CuCl microcrystallites in borosilicate glass near theZ3excitonic resonance. Induced index changes were estimated using Kramers–Kronig analyses of absorption bleaching data from 370 to 388 nm. The nonlinearity was found to increase with increasing particle radius over the range 22 to 34 A˚, in agreement with theoretical predictions.

ISSN:0003-6951    

DOI:10.1063/1.103441

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A novel method of simultaneous two‐way transmission over one fiber is described. Only one optical source is required. Transmission of signals exhibiting the same modulation speeds along the two directions of a single fiber is demonstrated using a coherence‐modulated light source. The first experimental results of a version of this system operating over 1 km of a multimode fiber are presented.

ISSN:0003-6951    

DOI:10.1063/1.103442

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A new technique for constructing multilayer dielectric mirrors is described that results in high reflectivities with only two or three dielectric layer pairs per mirror. These structures are obtained by selectively etching layered AlxGa1−xAs material grown by molecular beam epitaxy and then replacing the etched regions with acrylic resin or air. A thin optical cavity produced by this technique is demonstrated with mirror reflectivities near 96%. These techniques allow the fabrication of lasers, light‐emitting diodes, or optical switches with high contrast ratio mirrors on both sides of an optically active region in order to enhance output coupling, lower laser thresholds, and increase modulation rates.

ISSN:0003-6951    

DOI:10.1063/1.103443

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The linewidth enhancement factor &agr; in an InGaAs/InP strained‐layer multiple quantum well (MQW) laser emitting near 1.55 &mgr;m has been determined from the spontaneous emission spectra below threshold. The active layers in the MQW structure in this device are under 0.7% compressive strain. The measured &agr; at the lasing wavelength is 2.0. The calculation of &agr; using interpolated bandstructure parameters shows that it varies rapidly with injected carrier density and the calculated value for our device is close to the measured value. The small &agr; for strained MQW InGaAs lasers should result in performance improvement that are advantageous for lightwave system application.

ISSN:0003-6951    

DOI:10.1063/1.103444

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The first layer growth in GaAs molecular beam epitaxy has been studied by reflection high‐energy electron diffraction (RHEED). The time between the growth start and the first RHEED intensity peak is found to be dependent on the starting surface condition and is different from the time needed for a single layer growth. Periodic flux interruption has been used to study the surface recovery behavior as a function of growth time. When the growth time is the same as the time for a single layer growth, sustained two‐dimensional growth can be obtained.

ISSN:0003-6951    

DOI:10.1063/1.103445

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A (&sqrt;3×&sqrt;3)B structure was found to be formed on a (5×5) GexSi1−x/Si (111) surface on which Ga or Sn atoms did not form any superstructures. The critical B coverage at which a (7×7) pattern disappeared and only a (&sqrt;3×&sqrt;3) pattern was visible increased as the fraction (x) of Ge in the substrate layer increased. A Si epitaxial overlayer was grown on the (&sqrt;3×&sqrt;3)B/50 A˚ Ge0.4Si0.6/Si (111) structure at a growth temperature of 300 °C. The observed (−2/3,4/3) reflection intensity in grazing x‐ray diffraction was 50 times larger than that of a Si epitaxial layer grown on a (&sqrt;3×&sqrt;3)B/Si (111) structure under the same condition. On a GexSi1−xsubstrate, the B(&sqrt;3×&sqrt;3) structure is well preserved at the interface probably because of relief of the interface strain that results from the small size of the boron atom.

ISSN:0003-6951    

DOI:10.1063/1.104095

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

An alignment method for obtaining excellent surface stabilized ferroelectric liquid‐crystal devices is described. Alignment is obtained by obliquely depositing the SiO in two steps. The first deposition involves vacuum coating at 60° angle and the second at 85° (orthogonally to the first) with the substrate normal. The method induces a high (∼20°–25°) pretilt surface which depends on the thickness of the second layer. The glass substrates are matched with antiparallel direction of evaporation of second coating. This ensures a selective pretilt of molecules and the uniformly tilted smectic layer structure. The advantages of this new method are the ease of large‐scale production, defect‐free large uniform monodomains, good contrast, bistability, and microsecond switching speed response.

ISSN:0003-6951    

DOI:10.1063/1.103446

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Spontaneous vitrification was observed in the equilibrium immiscible Fe‐Cu system. The metastable phase before vitrification was an icosahedral incommensurate phase which was formed by an ion beam mixing of Fe‐Cu multilayer films at room temperature and subsequent high‐temperature thermal annealing. The electrical and magnetic properties of the icosahedral phase are also reported, and the relation with spontaneous vitrification is discussed.

ISSN:0003-6951    

DOI:10.1063/1.103447

出版商:AIP    

年代:1990

数据来源: AIP