摘要:

Noncollinearly phase‐matched second‐harmonic generation is reported for the first time in beta barium borate crystal and compared with existing KDP and KD*P crystals using Nd:YAG radiation.

ISSN:0003-6951    

DOI:10.1063/1.101405

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Light guiding and modulation was demonstrated in sputtered LiNbO3films deposited on glass substrates. We report on films’ exceptionally low attenuation (<2 dB/cm) and the highest electro‐optical coefficient reported so far for this kind of film (1.34×10−12m/V).

ISSN:0003-6951    

DOI:10.1063/1.101406

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

A short‐period (AlGaAs)m(GaAs)nsuperlattice has been applied to the barrier layers in a single and a multiple quantum well structure prepared by molecular beam epitaxy in order to improve the interface quality. With a 38 A˚ thin GaAs quantum well without employing aluminum, a low threshold current density of 260 A/cm2, a high characteristic temperature (T0) of 205 K, and a high differential quantum efficiency of 75% have been achieved in a double quantum well ridge waveguide laser diode emitting at 780 nm.

ISSN:0003-6951    

DOI:10.1063/1.100675

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Transverse‐mode‐stabilized ridge stripe AlGaInP semiconductor lasers fabricated using a thin GaAs layer as an etch stop are reproducibly realized. The ridge stripe structure is fabricated utilizing the large difference in etching rates between GaAs/AlGaAs and AlGaInP layers. As a result, the thickness control of the cladding layer adjacent to light absorbing layers is significantly improved. Results show that the GaAs layer is effective as an etch‐stop layer even if the thickness is only 1–2 nm. The total internal loss of the lasers is estimated to be about 20 cm−1and loss due to the insertion of the GaAs layer is almost negligible. A threshold current of about 50 mA and a stable fundamental transverse mode up to an output power of about 10 mW is attained at room temperature under cw operation. Similar results were obtained when an AlGaAs layer was used instead of GaAs.

ISSN:0003-6951    

DOI:10.1063/1.100676

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

An electro‐optic switch using total internal reflection by a ferroelectric liquid crystal is reported. The device has rise and fall times of about 150 &mgr;s, and causes the optical power in the output beam to be attenuated by a factor of 500 000 in the off state. It does not employ polarizers, and its operation is nearly independent of wavelength. The measurements here cover the 400–1600 nm band.

ISSN:0003-6951    

DOI:10.1063/1.100677

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

We report the first continuous‐wave (cw) photopumped operation of surface‐emitting lasers comprising pseudomorphic InGaAs quantum wells. The lasers were grown by molecular beam epitaxy and incorporate epitaxial quarter‐wave AlAs/GaAs mirrors surrounding an active region. In the active region, 50 A˚ InGaAs quantum wells are distributed with half‐wave periodicity to center on cavity standing wave maxima. Lasing is observed from 78 to 250 K in the spectral range 920–950 nm, where the GaAs substrate is transparent. Thresholds were as low as 1.5×104W/cm2, and overall (differential) output power efficiency was as high as 35% (85%) with up to 60 mW in a low divergence beam. Both periodic gain and biaxial compressive layer strain contribute to the reduced lasing threshold. The laser gain length is only 550 A˚ (11 quantum wells). The possibility of surface‐emitting lasing in single quantum wells is discussed.

ISSN:0003-6951    

DOI:10.1063/1.100678

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Lasing characteristics of optically pumped 1.5‐&mgr;m‐diam GaAs‐AlAs microresonators are reported. Room‐temperature thresholds of 9 pJ were observed. Uniform outputs were obtained from a simultaneously driven 2×2 array.

ISSN:0003-6951    

DOI:10.1063/1.100679

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

A practical difficulty in Monte Carlo simulations of electron transport occurs when the electron number density changes significantly over the time or length scale of the simulation. In this letter, we present a simple scaling procedure to resolve this difficulty that is easy to implement and that is exact for linear collision operators. A simulation of electron transport in nitrogen at high electric field strength is included to illustrate this rescaling procedure.

ISSN:0003-6951    

DOI:10.1063/1.100680

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Significantly improved spatial uniformity of bremsstrahlung radiation, relative to a planar‐anode diode, is obtained on the 3‐MV, 150‐kA HELIA accelerator when a B&thgr;lens diode is used to actively control the high‐power electron beam at the exit of a coaxial, magnetically insulated transmission line. The advantage of this diode over other diodes which only passively control the beam is that better radiation uniformity for less beam loss is possible. Measurements taken on HELIA are shown to agree with theoretical expectations.

ISSN:0003-6951    

DOI:10.1063/1.100681

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

A Brillouin scattering study of elastic properties of NbN/AlN superlattices is presented. Because the coupling of light to surface waves in this system is very weak, we describe a modification of the technique which enhances the scattering efficiency, thereby allowing measurements of a system which is otherwise inaccessible. This particular multilayer superlattice is one of the very few that does not exhibit any elastic anomalies as a function of layer thickness in accordance with the idea that electron transfer may be the mechanism responsible for elastic anomalies in superlattices.

ISSN:0003-6951    

DOI:10.1063/1.100682

出版商:AIP    

年代:1989

数据来源: AIP