摘要:

We demonstrate a practical four‐port flip chip end fire coupler useful for providing efficient coupling between single‐mode fibers and Ti‐diffused LiNbO3channel waveguides. Channel waveguide ends were prepared for coupling by cleavage. With a configuration suitable for multiple fiber coupling, coupling efficiencies up to 47% have been measured for TM polarization. Using micropositioners to align single input and output fibers with respect to the channel waveguide, end fire coupling efficiency was 58% (TM). The effect of waveguide mode mismatch and misalignment on coupling efficiency is investigated. We also observe double refraction and leaky mode propagation with TE polarized input to LiNbO3channel waveguides running perpendicular to the cleavage plane. With suitably prepared channel waveguides on LiTaO3, these effects are small or absent.

ISSN:0003-6951    

DOI:10.1063/1.90476

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

GaAs solar cells with conversion efficiencies as high as 14% at AM1 have been grown by the GaCl/AsH3hydride technique. Thin (∼200 A˚) layers of InGaP were used to passivate the GaAs top surface. We observe a 70‐fold increase in photoluminescence intensity of the GaAs after passivation, which is consistent with a lowering of the GaAs surface recombination velocity from ≳106to <104cm/sec. Short‐circuit current densities (Jsc) as high as 22 mA/cm2and open‐circuit voltages as high as 0.96 V were observed. (If achieved together, those values would yield an efficiency of almost 18%.)Vocwas observed to increase directly withp‐layer thickness (t), whereasJscdecreased directly witht. The efficiency also increased as the zinc doping was decreased.

ISSN:0003-6951    

DOI:10.1063/1.90477

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

An approximate analysis shows that rays guided inside a torus oscillate sinusoidally around the equator. Expressing the Helmholtz equation in toroidal coordinates yields the equivalent index of refraction. The equation can be solved, yielding Airy functions in the direction perpendicular to the surface. Along the surface the equation is similar to that for media with a quadratic index profile, the Hermite‐Gaussian solutions of which follow sinusoidal trajectories while oscillating in width. Experimental verification of these features is presented.

ISSN:0003-6951    

DOI:10.1063/1.90478

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

A quantum generalization of classical microwave mixer theory is developed to project the performance of nonlinear tunneling barriers at high frequencies. The results demonstrate that such devices may be considered photon detectors when their conductance varies rapidly on a scale of voltage h&slash;&ohgr;/e. Tunnel barrier mixers are thus shown to offer potential for the development of wide‐band quantum noise limited detectors in the wavelength region from 10 &mgr;m to a few millimeters.

ISSN:0003-6951    

DOI:10.1063/1.90479

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

We report the first excimer (XeF) pumping of Nd3+in a pentaphosphate (Nd : P5O14) host. Absorption of the XeF laser output of 3530 A˚ by the Nd3+transition (4I9/2→4D3/2) results in laser output at the 1.05‐&mgr; transition (4F3/2→4I11/2). Pumped in an oscillator configuration, threshold energy was only ≃3 mJ while slope efficiency was ≃1%. Temporal output consists of a single pulse of duration (FWHM) ≃6.6 ns; it arises due to the combination of short pump pulse (≃24 ns FWHM) and high gain of the pentaphosphate output. The device is expected to find considerable application in producing short (1–10 ns) pulses without the complication of aQswitch required in conventional flashlamp‐pumped lasers.

ISSN:0003-6951    

DOI:10.1063/1.90480

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The operation of a branching waveguide stripe‐geometry semiconductor injection laser is described. This structure produces interference fringes in the far field which are spatially scanned by electrically varying the optical phase in each leg of the branched waveguide in a manner analogous to microwave phased array radar. Moreover, the output spectral peak of the laser also varies periodically over 70 A˚ with these electrically induced phase shifts.

ISSN:0003-6951    

DOI:10.1063/1.90481

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Using the WKB approximation, we generalize Ulrich’s solution to the optimum coupling efficiency of a prism‐waveguide coupler, so that it can be applied to a waveguide with an arbitrary refractive‐index profile. As an example, we give an analytic solution to a waveguide having an exponential refractive‐index profile.

ISSN:0003-6951    

DOI:10.1063/1.90482

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

We report cw oscillation on five transitions of Cu+in the near infrared in hollow‐cathode He‐CuI, He‐CuBr, and He‐CuCl gas discharges. Excitation of the upper laser levels is attributed to thermal‐energy charge‐transfer reactions between ground‐state He ions and neutral Cu atoms following discharge dissociation of the Cu halide molecules to generate free copper in the volume. Operating temperatures are in the range 400–550 °C and threshold currents for oscillation compare favorably with the lowest yet reported for sputtering Cu+lasers.

ISSN:0003-6951    

DOI:10.1063/1.90483

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Operation of the nitrogen ion laser as an optical regenerative amplifier driven by a master oscillator allows the output to be effectively switched into the blue‐green region of the spectrum. In this work an amplifier containing a dilute plasma of nitrogen ions was pumped by thermolecular charge transfer from He2+produced by an intense e‐beam propagating through several atmospheres pressure of gas mixture. The injection of relatively broadband output from a dye laser oscillator caused the output from the amplifier to switch entirely into the (0,2) vibrational component of theB→Xelectronic transition of N+2at 470.9 nm. An output linewidth of 0.007 nm was achieved together with the early saturation of the laser transition needed for the extraction of power from the amplifier at optimal efficiency.

ISSN:0003-6951    

DOI:10.1063/1.90484

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The optical properties of buried‐heterostructure Ga1−xAlxAs lasers are carefully studied during accelerated aging at 70 °C. It is shown that neither kinks nor self‐pulsation is observed in the majority of the lasers after long‐term aging, in contrast to the observations in conventional stripe‐geometry lasers. The observed stable operation of buried‐heterostructure lasers may be attributed to the transverse‐mode stability and small cavity size intrinsic to the lasers.

ISSN:0003-6951    

DOI:10.1063/1.90442

出版商:AIP    

年代:1978

数据来源: AIP