摘要:

It is verified experimentally that the modulation frequency of modulational instability (MI) levels off to a certain upper limit by the fourth‐order dispersion of the optical fiber as the pump wavelength approaches the zero‐dispersion wavelength in the anomalous spectral region. Modulation frequencies observed in optical fibers with various dispersion values range up to 7 THz for an input intensity of 15 W/70 &mgr;m2. This agrees well with the recently reported theoretical prediction based upon the four‐photon mixing approach to MI.

ISSN:0003-6951    

DOI:10.1063/1.101075

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

A new gain mechanism active in certain quantum well laser diode structures is demonstrated and explained theoretically. It enhances the modulation amplitude produced by either optical or electrical modulation of quantum well structures. In the devices tested, power gains of 6 dB were measured from low frequency to frequencies of several gigahertz. Higher gains may be possible in optimized structures.

ISSN:0003-6951    

DOI:10.1063/1.101076

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Theoretical and experimental results are reported on electro‐optical switching in a GaAs‐based multiple quantum well coupled planar nonlinear optical directional coupler. It is shown that a careful selection of the wavelength of operation can lead to an efficient, practically constant loss, low electric field controlled transfer of light energy from one slab waveguide to the other. The quantum‐confined Stark effect in the multiple quantum well coupling layer is employed as the switching mechanism. Results are compared with those achieved with nonlinear all‐optical switching in the same structure. It is believed that this is the first semiconductor &Dgr;Kswitch.

ISSN:0003-6951    

DOI:10.1063/1.101077

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Lightweight Si/SiC mirrors of nominal diameter 7.5 cm have been fabricated via a scalable and rapid, chemical vapor deposition (CVD) process to demonstrate the CVD mirror fabrication technology. These mirrors consist of a faceplate of either Si or Si‐coated SiC and a lightweight backstructure made of either Si or SiC. The mirrors were polished to a figure better than 1/5th of a wave at 0.6328 A˚ and a finish of better than 10 A˚ rms. A procedure for fabricating these mirrors is described. The CVD fabrication process is fast and has the potential to yield several mirrors in a few weeks time from a single reactor. The CVD mirror fabrication technology is quite general and can be extended to include mirrors of other ceramic materials such as TiB2and B4C.

ISSN:0003-6951    

DOI:10.1063/1.101078

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Efficient coupling of long‐wavelength infrared (LWIR) radiation to a two‐dimensional (2‐D) array of GaAs/AlGaAs multiple quantum well detectors is achieved by illumination through chemically etched diffraction gratings. Gratings were fabricated on the back surface of the GaAs substrate as well as selectively on the top contact of the detector mesas. Both top and bottom illumination schemes were employed. In all cases, high coupling efficiency (>90%) of the gratings was observed as measured by comparing the responsivity to that of an identical detector illuminated through an angle‐polished facet. The results demonstrate the feasibility of high‐sensitivity GaAs LWIR imagers.

ISSN:0003-6951    

DOI:10.1063/1.101079

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

The gain‐loss laser oscillation condition is applied to photoexcitation geometries in which phonon‐assisted laser operation is observed in AlGaAs‐GaAs quantum well heterostructures (QWHs). The model is found to agree with a variety of experimental conditions in which cavity size, photoexcitation spot size, and mirror reflectivity are varied. Also, it serves to indicate further how others might have failed to observe phonon‐assisted laser operation in QWHs and how photoexcitation geometries can be varied to verify these results.

ISSN:0003-6951    

DOI:10.1063/1.101080

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

An anomalous dependence of the threshold current on the stripe width is observed for gain‐guided strained‐layer InGaAs/GaAs quantum well lasers. The threshold current increases strongly as the stripe width is reduced from relatively large values. This is attributed to the huge lateral loss caused by an unusually large index antiguide which manifests itself in the far‐field behavior. This large loss also leads to a population of higher quantized energy levels in the InGaAs quantum well strongly reducing the lasing wavelength by as much as 61 nm.

ISSN:0003-6951    

DOI:10.1063/1.101081

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

The second hyperpolarizability ⟨&ggr;xxxx⟩ of a new, soluble, conjugated polythiophene derivative, containing aromatic and quinoid moieties, is measured to be 1.2×10−31esu. The measurement was made at 532 nm in a dichloromethane solution by picosecond‐resolved degenerate four wave mixing. The corresponding macroscopic third‐order susceptibility &khgr;(3 )is estimated to be 4.6×10−9esu, which is larger than that of the parent poly(2,5‐thiophene) and many currently known nonlinear optical polymers.

ISSN:0003-6951    

DOI:10.1063/1.101082

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Strained‐layer Ga0.7In0.3As‐AlGaAs‐GaAs graded‐index separate confinement heterostructure single quantum well lasers have been grown by molecular beam epitaxy with growth conditions selected to optimize the growth of each material. The lasers emit at a wavelength of 1.03 &mgr;m at 300 K. These lasers have threshold currents of 12 mA for 3 &mgr;m×400 &mgr;m devices and average threshold current densities of 174 A/cm2for 40 &mgr;m×800 &mgr;m devices. Studies of threshold current versus cavity length and width are compared with theoretical formulations. The threshold currents for lasers of various lengths and widths are significantly lower than those for previous strained‐layer lasers grown by molecular beam epitaxy and lower than those for strained‐layer lasers grown by organometallic vapor phase epitaxy.

ISSN:0003-6951    

DOI:10.1063/1.101083

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

A laser interferometric method is described by which the length‐to‐voltage sensitivity of piezoelectric elements, as used e.g., in scanning tunneling microscopes, can be calibrated. The method is based on measuring the optical frequency of a laser locked to a piezoelectrically tuned interferometer, relative to a stable reference. The high sensitivity of this technique allows the calibration to be carried out in the low‐voltage regime.

ISSN:0003-6951    

DOI:10.1063/1.101064

出版商:AIP    

年代:1989

数据来源: AIP