摘要:

Complex refractive indices of a series of SiO2‐ and GeO2‐based glasses were measured to evaluate optical losses of hollow waveguides made of these glasses. Measured optical constants follow the well known dispersion formula and vary with the percentage of Si or Ge atoms to the whole cations. By using empirically defined relations between oscillation peaks and compositions, we can predict refractive indices and waveguide losses theoretically for the unknown SiO2‐ or GeO2‐based glasses.

ISSN:0003-6951    

DOI:10.1063/1.105095

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The thermal behavior of a Nd:YAG laser rod under flashlamp pumping has been investigated experimentally using a very simple interferometric technique. The degree of pumping uniformity and the heat generation rate inside the rod was evaluated for single pulse pumping. The temperature increase at the center of the rod under a high repetition rate pulsed operation was also measured, and this result is used to deduce the surface heat transfer coefficient.

ISSN:0003-6951    

DOI:10.1063/1.105096

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We report the observation of permanent photoinduced birefringence in a Ge‐doped fiber exposed to cw mode locked at 532 nm. This effect is enhanced by increasing the Ge concentration in the core of the fiber, or by submitting it to a thermal hydrogen treatment. The photoinduced birefringence is however very weak, or nonexistent, with irradiation by 514 or 488 nm cw argon laser light.

ISSN:0003-6951    

DOI:10.1063/1.105097

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Using solid source molecular beam epitaxy we have grown strained layer InGaAs/AlGaAs graded index separate confinement heterostructure lasers operating at 1.01 &mgr;m. For broad‐area, uncoated Fabry–Perot devices with cavity lengths in excess of 3000 &mgr;m, the threshold current density is 56 A/cm2, a value which we believe to be the lowest ever reported for laser diodes in any materials system. The internal quantum efficiency for these lasers is 88%, while the materials losses are 1.8 cm−1.

ISSN:0003-6951    

DOI:10.1063/1.105098

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Vanadium vapor is generated from a vanadium metal by irradiation of a pulsed YAG laser of 2.2 J energy, and the vanadium atoms are optically pumped by a XeCl laser of 7.3 mJ energy. Laser action has been observed on the vanadium 409.5 nm (4F07/2–4D5/2) transition. This laser pulse has a pulse width of 4 ns and peak power of 1.08 W, and the optical gain is 0.46/cm.

ISSN:0003-6951    

DOI:10.1063/1.105242

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Multiquantum barriers (MQBs) were introduced into 660 nm GaInP/AlInP lasers with superlattice confinement (SLC) layers, resulting in drastic improvements in lasing performance. Lowest threshold current densities (840 A/cm2) and highest room‐temperature values forT0(167 K) ever reported for 660–680 nm range lasers with bulk active layers were achieved. High‐temperature characteristics of the threshold current densities were measured in order to investigate the enhanced carrier confinement effect of MQBs and to estimate the excess nonradiative recombination current component. From the temperature dependence on the excess current density, the activation energiesE0of nonradiative processes were estimated to be 0.45 eV for MQB‐SLC lasers, and 0.26 eV for conventional SLC lasers without MQB. The increase ofE0demonstrates the enhanced heterobarrier effect by MQBs.

ISSN:0003-6951    

DOI:10.1063/1.105099

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The NaCl:Eu2+thermoluminescence characteristics after ultraviolet irradiation as well as solar exposure have been analyzed. The TL excitation spectra of this material is coincident with the actinic region and its sensibility limit is less than 0.2 &mgr;J/cm2for 240 nm wavelength irradation. A model for the thermoluminescence emission is provided.

ISSN:0003-6951    

DOI:10.1063/1.105100

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Tunable, single longitudinal mode spectrum of a novel monolithic, laterally coupled semiconductor stripe laser has been demonstrated. A tuning range of 14.2 nm, which is the widest observed so far in a monolithic device, has been achieved.

ISSN:0003-6951    

DOI:10.1063/1.105101

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The coupling of an interdigital transducer to ultrasonic Lamb waves propagating in a piezoelectric plate has been calculated using Green’s function method. It is found that when the plate thickness is more than a few acoustic wavelengths, the lowest order symmetric (S0) and antisymmetric (A0) modes are almost equally generated. The slight difference in the velocities of these modes gives rise to the beating effect whereby wave energy transfers periodically between the upper and lower plate surfaces. Experimental measurements performed on aY‐cut,Z‐propagating lithium niobate plate are found to be in good agreement with theoretical predictions. The coupling coefficients have also been calculated using the simpler definitionK2= 2(v0−vm)/v0, wherev0andvmare Lamb wave velocities on a free and metallized surface, respectively. It is found that this definition gives erroneous results if the ratio of plate thickness to acoustic wavelength is greater than 1.

ISSN:0003-6951    

DOI:10.1063/1.105102

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

When the maximum temperatures within a high‐pressure gas discharge arc are lower than the ionization temperature of the gas molecules by an order of magnitude, an asymptotic treatment of the temperature equation is possible. This is illustrated by means of the Elenbaas–Heller equation [e.g., M. F. Hoyaux,ArcPhysics(Springer, Berlin, 1968), p. 36] for a nonradiating wall‐stabilized arc. The asymptotics lead to a closed‐form expression for the relationship between the arc current and the axis temperature. An expression for the heat loss per unit length is also given.

ISSN:0003-6951    

DOI:10.1063/1.105103

出版商:AIP    

年代:1991

数据来源: AIP