摘要:

This letter presents a self‐consistent nonlinear treatment of three‐dimensional effects associated with the wiggler field, the electron beam, and the radiation beam in a steady‐state free electron laser (FEL) amplifying configuration. Our formulation also incorporates various efficiency enhancement schemes. We find that the 3‐D effects can lead to substantial differences in the results compared to the 1‐D theory. Finally a 3‐D numerical illustration of a 10.6‐&mgr;m FEL is given.

ISSN:0003-6951    

DOI:10.1063/1.92866

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

We discuss a refined, hybrid rf/optical technique for studying sub‐Doppler saturated absorption/dispersion resonances with excellent precision and symmetry. Sensitivity is limited mainly by fundamental noise in the signal. Resonance profiles obtained inI2are in remarkable agreement with theory. The method promises a new level of accuracy for laser locking to an optical resonance.

ISSN:0003-6951    

DOI:10.1063/1.92867

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

The cw accelerated aging behavior of proton‐bombarded stripe geometry lasers fabricated from MBE grown DH wafers have been studied. The laser diodes were formed into a 5‐&mgr;m‐wide shallow proton‐irradiated stripe geometry and operated without mirror coatings in dry nitrogen 70 °C ambients at constant power outputs of 2.5 mW and 3.0 mW/mirror. A feasibility demonstration of long lifetimes was obtained for lasers from three selected MBE wafers; where a median lasing lifetime of 8800 h with a standard deviation of 1.5 was found at 70 °C, which projects to a mean laser lifetime ≳106h at room temperature. After initial aging, long‐term degradation rates as low as 0.7 mA/kh for the operating current at 70 °C have been measured. The present results also show that the rate of change of the operating current with aging for MBE diodes is more uniform than for typical LPE diodes fabricated with the same technology. Data are presented for lasers from one of the wafers that show that after 1500 h of 70 °C cw aging, many of the electrooptical characteristics are relatively unchanged.

ISSN:0003-6951    

DOI:10.1063/1.92868

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

Transition moments and energies have been calculated for the X‐A, bound to continuum, transition in HgBr. Absorption at the laser wavelength of 502 nm has been examined for two sets of absorbing states: A thermal distribution of vibrational levels at 500° K and the terminus vibrational level of the B‐X laser transition. In the first case a cross section of 7×10−20cm2is calculated. Since no fast reaction for removal of the X state is known, the number density can exceed 1016cm−3and a significant absorption will result in late times. In the second case the laser photon can be coherently absorbed in the X‐A transition leading to photon induced predissociation of thev= 0, B state. An upper bound to the predissociation rate for a 2‐MW/cm2s flux is 106s−1. Electron dissociative attachment of the X state is also shown to be improbable as a means of fast removal. Energy curves of the ground states of both the neutral and negative ion of HgBr are shown not to cross in any accessible region.

ISSN:0003-6951    

DOI:10.1063/1.92869

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

A comparison of measured and predicted signal‐to‐noise ratio is made in an optical heterodyne spectrometer utilizing a tunable diode laser which exhibited excess noise. It is shown that good agreement between predicted and measured signal‐to‐noise ratios results if excess noise effects due to tunable diode lasers are included in the predictions. The methods used to quantify excess noise and to incorporate their effects into predictions of signal‐to‐noise ratio are discussed.

ISSN:0003-6951    

DOI:10.1063/1.92870

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

A3He‐Xe gas mixture, excited by the3He(n,p)3H reaction, has been employed to amplify the output of a3He‐Xe direct nuclear‐pumped laser. Lasing occurred on the 2.63‐&mgr; of XeI in the oscillator. The oscillator output was reflected through 180 ° and passed through the amplifier system. Power measurements of the oscillator output and the amplifier output show the laser power to be amplified by a factor of 3 for the3He‐Xe system. Amplification by a factor of 5 was obtained for a3He‐CO system.

ISSN:0003-6951    

DOI:10.1063/1.92871

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

The backscattered light amplitude is measured from one end of a fiber as a function of optical frequency by tuning a HeNe laser over its linewidth. Fourier transform by a low‐frequency electronic spectrum analyzer then reveals the spatial distribution of scattering and of the fiber losses.

ISSN:0003-6951    

DOI:10.1063/1.92872

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

A method for the generation and amplification of infrared and optical radiation is presented based on space‐charge interaction of electron streams of different momentum. The use of relativistic electrons with low‐energy dispersion is found to allow gain to occur at infrared and optical wavelengths.

ISSN:0003-6951    

DOI:10.1063/1.92873

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

The propagation of horizontally polarized shear (SH) waves through an austenitic stainless steel weld metal‐base metal interface is described. It is shown that SH wave probing signals are particularly suitable for nondestructive evaluation of those stainless steel weldments that are very difficult to evaluate using vertically polarized shear and longitudinal wave probing signals. The SH wave technique is demonstrated experimentally on a 304L/316L stainless steel butt weldment using 454‐kHz SH wave electromagnetic‐acoustic transducers that excite SH wave probing signals at 70° with respect to surface normal.

ISSN:0003-6951    

DOI:10.1063/1.92853

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

We discuss the director deformation near the interface between a liquid crystal and a solid substrate. The gradient of the tilt angle at the interface was measured by Sprokeletal. as a function of an applied voltage; they obtained a larger gradient than that calculated from Frank theory by a factor of about 5. In order to explain the abnormal gradient, we have taken into account the balance of torque at the interface. The gradient of tilt was estimated when the higher voltage is applied to the liquid crystals; the estimated result agrees well with their experimental result.

ISSN:0003-6951    

DOI:10.1063/1.92854

出版商:AIP    

年代:1981

数据来源: AIP