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in subjects: "Coherent Radiation"

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Adiabatic following in two-photon transition

There has been much interest recently in coherent multiphoton transitions in many-level systems. The present work considers the effect of relaxation in the response of a three-level system to a smoothly varying, near-resonant, two-photon field. The relaxation-dependent contributions to the nonlinear refractive index are calculated. It is shown that the coherent interaction of two smoothly varying, near-resonant, two-photon pulses with a three-level system can be described by ''two-photon damped… more

Date: January 1, 1977

Creator: Nayfeh, M. H. & Nayfeh, A. H.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Condensed Matter Research Using the UCSB FEL. [Univ. of California, Santa Barbara Free Electron Laser project]

The University of California, Santa Barbara (UCSB) Free Electron Laser (FEL) project was initiated in 1981 to test the idea of using an electrostatic accelerator in a recirculating beam mode to produce high-power, continuously tunable, coherent far infrared radiation. The development and application of this device to condensed matter research are briefly recounted. Emphasis was on semiconductor research and two-photon experiments. (RWR)

Date: January 1, 1992

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Harmonic generation mechanisms in short-wavelength free-electron lasers

The physical mechanisms that contribute to harmonic radiation in free-electron laser systems are examined. Mathematical models for the spontaneous and coherent-spontaneous emission in plane-polarized wigglers are given. How these models are used to perform numerical simulations is discussed. Modifications of the models to incorporate non-ideal free-electron laser effects are reviewed. 19 refs., 4 figs.

Date: January 1, 1990

Creator: Schmitt, M. J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Channeling and coherent bremsstrahlung effects for relativistic positrons and electrons. [16 to 28 MeV, orientation]

Channeling of positrons in single crystals of silicon was observed in transmission and scattering measurements for incident energies from 16 to 28 MeV. In addition, the spectral dependence upon crystal orientation of the forward coherent bremsstrahlung produced by beams of 28-MeV positrons and electrons incident upon a 5 ..mu..m thick single crystal of silicon was measured with a NaI photon spectrometer. Effects of channeling and perhaps of the nonvalidity of the first Born approximation were o… more

Date: March 22, 1976

Creator: Walker, R. L.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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INVESTIGATION OF COHERENT EMISSION FROM THE NSLS VUV RING.

Bursts of coherent radiation are observed from the NSLS VUV ring near a wavelength of 7 mm. The bursts occur when the electron beam current (I) exceeds a threshold value (I{sub th}), which itself varies with ring operating conditions. Beyond threshold, the average intensity of the emission is found to increase as (I-I{sub th}){sup 2}. With other parameters held nearly constant, the threshold current value is found to increase quadratically with synchrotron frequency, indicating a linear depende… more

Date: March 1, 1999

Creator: Carr, G. L.; Kramer, S. L.; Murphy, J. B.; Laveigne, J.; Lobo, R. P. S.; Reitze, D. H. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Observation of coherent resonance fluorescence in hot CO/sub 2/

Hot CO/sub 2/ was used to check theoretical understanding by using one-nanosecond pulses. The results reported are in relatively good agreement with theory. The experimental setup consisted of a one nanosecond duration 1/2 millijoule switched-out pulse directed through two heated pyrex cells filled with CO/sub 2/ and fitted with NaCl windows at Brewster's angle. The cells were 190 cm long of which 160 cm were heated to 300 +- 10/sup 0/C for a total heated path of 320 cm. Results are shown. They… more

Date: January 1, 1976

Creator: Czuchlewski, S. J.; Feldman, B. J.; Fisher, R. A. & Nowak, A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Focusing Hard X-rays at Current and Future Light Sources for Microscopy and High-Power Applications

The field of x-ray optics struggles to develop optical systems with the versatility and sophistication of their visible light counterparts. The advent of fourth-generation light sources will make the struggle even more difficult. Fourth-generation light sources include laser/plasma sources, x-ray Free Electron Lasers (FEL), inverse Compton scattering sources, and the National Ignition Facility. LCLS, (Linac Coherent Light Source), and its European cousin, will be the first of the x-ray FELs. Th… more

Date: March 16, 2004

Creator: Bionta, R M

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Summary of the linac based radiation sources working group

Technological advances have occurred in the past few years that have made linac based Free-Electron Lasers (FEL) promising candidates for the generation of short wavelength radiation. Although the FELs use undulators or wigglers, they produce stimulated radiation rather than the spontaneous emission found in insertion devices on the second and third generation sources of today. This stimulated emission process endows the FEL with properties presenting unique opportunities in many fields of scie… more

Date: October 1, 1992

Creator: Ben-Zvi, Ilan; Corbett, J.; Johnson, E.; Kim, K. J. & Sheffield, R.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Instantaneous frequency dynamics of coherent emission from magnetoexcitons in gallium arsenide

By time resolving the power spectrum of the ultrafast four wave mixing emission from the lowest magnetoexciton in GaAs, the authors determine the origin of the very complicated dynamics observed in the time domain.

Date: May 1, 1994

Creator: Mycek, M. A.; Siegner, U. & Chemla, D. S.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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High-order sum and difference-frequency generation in helium

High-order harmonic generation provides a new method for generating coherent, XUV radiation. These harmonics are characterized by a rapid, pertubative drop at low orders, followed by a broad plateau extending to photon energies of 150 eV in the lighter, rare gas atoms. An experimentally observed limit coincides with the theoretical limit for harmonic generation in neutral atoms given by the expression E{sub c}(eV)=IP(0)+3U{sub p}(I), where E{sub c} is the energy cutoff of the harmonic plateau, … more

Date: May 12, 1993

Creator: Crane, J. K. & Perry, M. D.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Temporal and spectral investigation of multi-Landau level quantum beats in GaAs

By resolving temporally and spectrally transient four-wave-mixing, the authors observe multiple Landau level quantum beating in GaAs under 6T magnetic field. Excitation energy and density dependent quantum interference gives rise to non-periodic beats.

Date: May 1, 1994

Creator: Siegner, U.; Mycek, M. A. & Chemla, D. S.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Coherent multiple-foil x-ray transition radiation

Intense x-ray transition radiation can be generated when relativistic electrons pass through a multiple-foil target. When the foil spacing is periodic, the transition radiation can be spatially coherent with respect to the target period. The spatial coherence can be evident in the spectra and angular distributions of transition radiation from such targets. A series of experiments has measured coherent transition radiation distributions from multiple-foil targets (up to six foils) with spacings … more

Date: August 25, 1993

Creator: Moran, M. J.; Chang, B. & Schneider, M. B.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Third generation synchrotron radiation applied to materials science

Utility of synchrotron radiation for characterization of materials and ramifications of availability of new third-generation, high-energy, high-intensity sources of synchrotron radiation are discussed. Examples are given of power of x-ray analysis techniques to be expected with these new machines.

Date: November 1, 1993

Creator: Kaufmann, E. N. & Yun, W.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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A 2--4 nm Linac Coherent Light Source (LCLS) using the SLAC linac

We describe the use of the SLAC linac to drive a unique, powerful. short wavelength Linac Coherent Light Source (LCLS). Operating as an FEL, lasing would be achieved in a single pass of a high peak current electron beam through a long undulator by self-amplified spontaneous emission (SASE). The main components are a high-brightness rf photocathode electron gun; pulse compressors; about 1/5 of the SLAC linac; and a long undulator with a FODO quadrupole focussing system. Using electrons below 8 G… more

Date: May 1, 1993

Creator: Winick, H.; Bane, K. & Boyce, R.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Anomalous dispersion enhanced Cerenkov phase-matching

The authors report on a scheme for phase-matching second harmonic generation in polymer waveguides based on the use of anomalous dispersion to optimize Cerenkov phase matching. They have used the theoretical results of Hashizume et al. and Onda and Ito to design an optimum structure for phase-matched conversion. They have found that the use of anomalous dispersion in the design results in a 100-fold enhancement in the calculated conversion efficiency. This technique also overcomes the limitatio… more

Date: November 1, 1993

Creator: Kowalczyk, T. C.; Singer, K. D. & Cahill, P. A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Coherence and linewidth studies of a 4-nm high power FEL

Recently the SSRL/SLAC and its collaborators elsewhere have considered the merits of a 2 to 4-nm high power FEL utilizing the SLAC linac electron beam. The FEL would be a single pass amplifier excited by spontaneous emission rather than an oscillator, in order to eliminate the need for a soft X-ray resonant cavity. We have used GINGER, a multifrequency 2D FEL simulation code, to study the expected linewidth and coherence properties of the FEL, in both the exponential and saturated gain regimes.… more

Date: May 1, 1993

Creator: Fawley, W. M.; Sessler, A. M. & Scharlemann, E. T.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Proposal for the experimental demonstration of the coherent radiation

It is of great importance to provide an experimental demonstration of the coherence of the radiation of electromagnetic waves from a short bunch of electrons performing oscillations in a direction transverse to the main direction of motion. It is known that electrons circulating in a storage ring lose energy to synchrotron radiation. Another method to stimulate radiation is to let an electron bunch travel through a wiggler or an ondulator device. In either case the spectrum usually peaks in cor… more

Date: August 1, 1992

Creator: Ruggiero, Alessandro G.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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X-ray laser `` oscillator-amplifier`` experiments

We present results from experiments directed toward increasing the degree of transverse coherence in x-ray laser beams. We have concentrated on the neon-like yttrium (Z=39) collisionally-pumped x-ray laser as the test system for these studies because of its unique combination of brightness, monochromaticity, and high-reflectivity optics availability. Attempts at improving laser performance using proximate feedback optics failed. Modest success has been found to date in ``double foil`` experimen… more

Date: March 19, 1993

Creator: Shimkaveg, G. M.; Carter, M. R.; Young, B. K. F.; Walling, R. S.; Osterheld, A. L.; Trebes, J. E. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Beam emittance from coherent Cherenkov radiation in a solid dielectric

We report experimental insults of a technique for direct measurement of the emittance in high energy beams. This technique is analogous to the well known ``pepper pot`` masking approach, but with no upper limit on particle energy. Single shot emittance profiles were obtained on the 10 kA, 4 MeV SNL electron Recirculating Linear Accelerator showing agreement with theory and with alternate emittance measurements. Coherent (i.e., not strongly scattered or diffused) Cherenkov radiation from a flat,… more

Date: June 1, 1993

Creator: Richardson, R. D.; Platt, R. C. & Crist, C. E.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Phase dynamics of non-equilibrium distributions of free electron-hole pairs in GaAs quantum wells

The authors resolve the phase and amplitude of the coherent emission of a non-equilibrium Fermi-Sea in four wave mixing experiments. It exhibits an ultrafast dynamical blue shift, due to Fermi-edge many-body effects.

Date: May 1, 1994

Creator: Bigot, J. Y.; Mycek, M. A.; Weiss, S. & Chemla, D. S.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Towards spectroscopy of partially coherent sources

Traditional spectroscopy is concerned with spatially incoherent sources. In relatively recent times, after the invention of the lasers in 1960, spectroscopy of coherent sources has also been gradually developed. In the last few years it was found that spectroscopy of partially coherent sources i.e., those which are neither completely uncorrelated nor fully correlated, encounters certain problems. They arise from the fact predicted theoretically in 1986 and confirmed experimentally soon afterwar… more

Date: December 31, 1991

Creator: Wolf, E.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Condensed Matter Research Using the UCSB FEL. Final technical report, May 1, 1984--January 31, 1992

Date: September 1, 1992

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Coherence properties of high order harmonic radiation

The results of a series of experiments to characterize the coherence properties of xuv radiation produced by high-order harmonic generation in helium, neon and argon are reported and compared to predictions from an effective order model. The harmonics exhibit smooth, near gaussian spatial profiles, and have a divergence that is approximately constant ( < 12 mrad) in the plateau region and decreases ({approx}4 mrad) in the cutoff for f/17 focusing. For a bandwidth limited, 140 fsec incident puls… more

Date: May 1, 1994

Creator: Ditmire, T.; Budil, K. S.; Crane, J. K.; Nguyen, H.; Perry, M. D.; Salieres, P. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Using coherent illumination to extend HRTEM resolution: Why we need a FEG-TEM for HREM

Resolution of a high-resolution transmission electron microscope (HRTEM) has traditionally been defined in terms of its Scherzer resolution limit at optimum defocus. However, even beyond the Scherzer limit, spatial frequencies can be transferred from the specimen to the image, out to the so-called information limit of the electron microscope. The information limit of the HRTEM is determined by the degree of energy spread in the electron beam used to illuminate the sample. Since a HRTEM equipped… more

Date: November 1, 1992

Creator: O`Keefe, M. A.

Item Type: Article

Partner: UNT Libraries Government Documents Department