摘要:

Results of the implementation of a distributed feedback (DFB) reflector in a free‐electron laser (FEL) are described. The reflector was positioned in the interaction region of the FEL waveguide in order to produce narrow bandwidth features in the output spectrum. Both the DFB and wiggler were of helical configuration. The energy, current, and pulse width of the electron beam were 1.5 MeV, 100 A, and 50 ns. By employing the DFB structure the intensity of the two specific frequencies may be increased by factors of 3 and 5. These frequencies are in good agreement with those predicted by theory. Temporally radiation waveforms exhibit a double peak, revealing a sensitivity of the oscillation condition to beam energy.

ISSN:0003-6951    

DOI:10.1063/1.102775

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We describe a technique to extract electro‐optic Cherenkov radiation from a LiTaO3crystal into free space. This permits the generation of collimated beams of terahertz radiation into free space and overcomes previous limitations imposed by total internal reflection.

ISSN:0003-6951    

DOI:10.1063/1.103299

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

An electro‐optic phase modulator and a switched directional coupler are integrated on a common LiNbO3substrate and inserted into the cavity of a 3‐m‐long Nd3+single‐mode fiber laser (&lgr;≊1088 nm). Their simultaneous operation yields groups of ≊10 pulses at rates up to 2 kHz, with 50 ps pulse duration, 30 ns separation, and 200 W peak power.

ISSN:0003-6951    

DOI:10.1063/1.102751

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The nonlinear frustrated‐total‐reflection filter is proposed as a remarkably simple all‐optical computing element. Potential advantages of this device over nonlinear prism couplers and nonlinear thin films are presented. Optical bistability is experimentally demonstrated by using a liquid crystal as an optically nonlinear material.

ISSN:0003-6951    

DOI:10.1063/1.102752

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A full‐wave analysis of the dispersion in coplanar‐type transmission lines is made including the effect of material dispersion arising from a frequency‐dependent complex dielectric constant such as due to optical phonon resonances in the substrate. The results are used to examine the distortion of femtosecond electrical pulses propagating in coplanar striplines made on ultrathin as well as thick GaAs substrates. A new closed‐form dispersion formula for coplanar lines is also reported, valid for complex dielectric constants and all values of frequency and line dimensions.

ISSN:0003-6951    

DOI:10.1063/1.102753

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

An optical modulation technique is used to determine three important parameters for 1.3 &mgr;m InGaAsP diode lasers: the rate of spontaneous emission into the guided modes, the nonlinear gain coefficient, and the carrier lifetime at threshold. These results are unaffected by electrical parasitics, and are essential to understanding the noise and modulation properties of diode lasers.

ISSN:0003-6951    

DOI:10.1063/1.102754

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We demonstrate a new technique for displaying the electric field autocorrelation function of a laser pulse in real time, using two‐beam coupling in a photorefractive crystal. This technique does not require phasematching, is simple to align, and can be used over the entire visible and near‐infrared regions of the spectrum, even with weak laser beams.

ISSN:0003-6951    

DOI:10.1063/1.102755

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A new method of electro‐optic sampling field transients, using above‐band‐gap optical probes in reflection, is analyzed theoretically and experimentally demonstrated to be within a factor of 2 as sensitive as electro‐optic sampling in transmission. The technique is ideally suited to the study of interfaces due to the surface selective nature of the evanescent field probe. Studies of the dynamics of photogenerated electron‐hole pair separation in surface‐space‐charge fields at GaAs(100)/oxide interfaces show that the hole carrier transit time is faster than 500 fs. Using longitudinal electro‐optic sampling beam geometries, this technique has an intrinsic resolution of 50 fs.

ISSN:0003-6951    

DOI:10.1063/1.102734

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Ferroelectric BaTiO3thin films were directly and epitaxially grown on SrTiO3single crystal and epitaxial Pt film substrates by activated reactive evaporation. The substrate temperature was around 600 °C. For (100) oriented as‐grown films, a typical ferroelectric hysteresis loop and a maximum of dielectric constant at about 115 °C were observed. The resistivity was as high as 109&OHgr; cm and the breakdown voltage was 2.7 MV/cm for as‐grown BaTiO3films.

ISSN:0003-6951    

DOI:10.1063/1.103300

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A 6H&agr;‐SiC crystal sample, which has a surface amorphous layer resulting from a high‐dose Ga implantation, was heated using a pulsed excimer laser at several energy fluences. At an energy fluence of 1.66 J/cm2, theinsitureflectivity measurement of the surface during laser processing indicates that melting of the SiC surface has occurred. Rutherford backscattering and channeling analysis shows that the molten amorphous SiC recrystallizes using the substrate as a seed, and that the recrystallized layer has good crystal quality. Secondary‐ion mass spectrometry measurements indicate that the melting, resulting from the excimer laser pulse, results in significant redistribution of the implanted Ga. This result, the first reported for SiC, suggests that the pulsed ultraviolet process can anneal the implantation damage through a melt recrystallization process, and thus could be used to dope SiC through a gas phase adsorption process.

ISSN:0003-6951    

DOI:10.1063/1.102735

出版商:AIP    

年代:1990

数据来源: AIP