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in subjects: "Harmonic Generation"

open access

The Fresh-Bunch' technique in FELs

The 'Fresh Bunch' technique is being proposed as a method of increasing the gain and power of FEL amplifiers in which the length of the optical radiation pulse is shorter than the length of the electron bunch. In multi-stage FEL, electron beam energy spread is increased by the FEL interaction in the early stages. In the 'Fresh Bunch' technique, the low energy spread of the electron beam is recovered by shifting the radiation pulse to an undisturbed part of the electron bunch, thus improving the… more

Date: January 1, 1991

Creator: Ben-Zvi, Ilan; Yang, K. M. & Yu, L. H.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Nonlinear spectroscopic studies of interfacial molecular ordering

The second order nonlinear optical processes of second harmonic generation and sum frequency generation are powerful new probes of surfaces. They possess unusual surface sensitivity due to the symmetry properties of the nonlinear susceptibility. In particular, infrared-visible sum frequency generation (SFG) can obtain the vibrational spectrum of sub-monolayer coverages of molecules. In this thesis, we explore the unique information that can be obtained from SFG. We take advantage of the sensiti… more

Date: July 1, 1991

Creator: Superfine, R.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Synthesis and characterization of a covalently bound self-assembled macrocycle monolayer thin film for nonlinear optical materials

Synthesis and characterization of covalently bound self-assembled, 5,10,15,20-Tetra(4-pyridyl)-21H,23H-porphine monolayer superlattices on various oxide surfaces such as fused silica, glass or silicon are described. The mono-molecular thin film structures are characterized by UV-visible ({lambda}{sub max} = 447 nm) and FTIR-ATR spectroscopy. In addition, X-ray photoelectron spectroscopy and secondary ion mass spectroscopy studies are used to confirm the formation of a self-assembled monolayer o… more

Date: January 1, 1992

Creator: Li, DeQuan; Swanson, B. I.; Robinson, J. M. & Hoffbauer, M. A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Atomic physics in strong fields

This report discusses: Microwave Driven Multiphoton Excitation Dynamics in Rydberg Atoms; Nonadiabatic Geometric Phases of Multiphoton Transitions in Dissipative Systems and Spin-j Systems; and Nonperturbative Treatments of Atomic and Molecular Processes in Intense Laser Fields.

Date: April 1, 1992

Creator: Chu, Shih-I.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Conformation, Orientation and Interaction in Molecular Monolayers: A Surface Second Harmonic and Sum Frequency Generation Study

We have used sum frequency generation (SFG) to study the order in a silane monolayer before and after the deposition of a coadsorbed liquid crystal monolayer. We observe an increase in the order of the chain of the silane molecule induced by the interpenetration of the liquid crystal molecules. By using second harmonic generation (SHG) and SFG, we have studied the orientation and conformation of the liquid crystal molecule on clean and silane coated glass surfaces. On both surfaces, the bipheny… more

Date: December 1, 1988

Creator: Superfine, R.; Huang, J.Y. & Shen, Y.R.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Electrical characterization of rf plasmas

Radio-frequency (rf) electrical sources are commonly used to generate plasmas for processing of industrial materials and for related experimental work. Published descriptions of such plasmas usually include generator-power measurements, and occasionally include plasma dc-bias measurements. One or both of these quantitites are also used in industrial feedback ccontrol systems for setpoint regulation. Recent work at Sandia an elsewhere with an experimental rf discharge device (the GEC RF Referenc… more

Date: August 1, 1991

Creator: Miller, P.A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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The Los Alamos POP Project: FEL oscillator experiments in the ultraviolet and beyond

The Los Alamos POP Project will include a series of proof-of-principle FEL oscillator experiments in 1992 designed to extend FEL operation into the ultraviolet (UV) and vacuum ultraviolet (VUV). With beam energy extended to 50 MeV, enhanced beam brightness with a photoinjector, and appropriate UV and VUV resonator optics, the Los Alamos FEL oscillator should have sufficient single-pass gain (20--30%) to reach below 200 nm. The first goal will be lasing at 250 nm utilizing a permanent-magnet und… more

Date: January 1, 1992

Creator: Newnam, B. E.; Warren, R. W.; Goldstein, J. C.; Schmitt, M. J.; Bender, S. C.; Carlsten, B. E. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

A High Repetition Rate VUV-Soft X-Ray FEL Concept

We report on design studies for a seeded FEL light source that is responsive to the scientific needs of the future. The FEL process increases radiation flux by several orders of magnitude above existing incoherent sources, and offers the additional enhancements attainable by optical manipulations of the electron beam: control of the temporal duration and bandwidth of the coherent output, reduced gain length in the FEL, utilization of harmonics to attain shorter wavelengths, and precise synchron… more

Date: June 24, 2007

Creator: Corlett, J.; Byrd, J.; Fawley, W. M.; Gullans, M.; Li, D.; Lidia, S. M. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

LDRD final report on continuous wave intersubband terahertz sources.

There is a general lack of compact electromagnetic radiation sources between 1 and 10 terahertz (THz). This a challenging spectral region lying between optical devices at high frequencies and electronic devices at low frequencies. While technologically very underdeveloped the THz region has the promise to be of significant technological importance, yet demonstrating its relevance has proven difficult due to the immaturity of the area. While the last decade has seen much experimental work in ult… more

Date: February 1, 2005

Creator: Samora, Sally; Mangan, Michael A.; Foltynowicz, Robert J.; Young, Erik W.; Fuller, Charles T.; Stephenson, Larry L. et al.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Effects of Energy Chirp on Echo-Enabled Harmonic Generation Free-Electron Lasers

We study effects of energy chirp on echo-enabled harmonic generation (EEHG). Analytical expressions are compared with numerical simulations for both harmonic and bunching factors. We also discuss the EEHG free-electron laser bandwidth increase due to an energy-modulated beam and its pulse length dependence on the electron energy chirp.

Date: February 23, 2009

Creator: Huang, Z.; Ratner, D.; Stupakov, G. & Xiang, D.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Electron Dynamics of Silicon Surface States: Second-Harmonic HoleBurning on Si(111)7x7

The ultrafast dynamics of electronic excitations of the surface dangling bond states of Si(111) 7 x 7 has been investigated by second harmonic generation as a probe of transient spectral hole burning. Spectral holes induced by a 100 fs pump at {approx_equal} 1.5 eV and their decay are interpreted in terms of electronic dephasing times as short as 15 fs. This fast time scale together with the strong excitation-induced dephasing observed is interpreted in terms of carrier-carrier scattering. In a… more

Date: June 6, 2005

Creator: McGuire, John A.; Raschke, Markus B. & Shen, Yuen-Ron

Item Type: Article

Partner: UNT Libraries Government Documents Department

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A table-top femtosecond time-resolved soft x-ray transient absorption spectrometer

A laser-based, table-top instrument is constructed to perform femtosecond soft x-ray transient absorption spectroscopy. Ultrashort soft x-ray pulses produced via high-order harmonic generation of the amplified output of a femtosecond Ti:sapphire laser system are used to probe atomic core-level transient absorptions in atoms and molecules. The results provide chemically specific, time-resolved dynamics with sub-50-fs time resolution. In this setup, high-order harmonics generated in a Ne-filled c… more

Date: May 21, 2008

Creator: Leone, Stephen; Loh, Zhi-Heng; Khalil, Munira; Correa, Raoul E. & Leone, Stephen R.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Running Shanghai Soft x-ray FEL with the EEHG scheme

With the nominal beam parameters (beam energy: 0.84 GeV, slice energy spread: 168 keV, peak current: 600 A, normalized emittance: 2 mm mrad) of the Shanghai soft X-ray Free Electron Laser (SXFEL) project, we show that using the echo-enabled harmonic generation (EEHG) scheme, 9 nm coherent soft x-ray with peak power exceeding 400 MW can be generated directly from the 270 nm seeding laser.

Date: December 18, 2008

Creator: Xiang, D. & Stupakov, G.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Three-dimensional analysis of free-electron laser performance using brightness scaled variables

A three-dimensional analysis of radiation generation in a free-electron laser (FEL) is performed in the small signal regime. The analysis includes beam conditioning, harmonic generation, flat beams, and a new scaling of the FEL equations using the six-dimensional beam brightness. The six-dimensional beam brightness is an invariant under Liouvillian flow; therefore, any nondissipative manipulation of the phase-space, performed, for example, in order to optimize FEL performance, must conserve thi… more

Date: June 11, 2008

Creator: Penn, Gregory; Gullans, M.; Penn, G.; Wurtele, J.S. & Zolotorev, M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Tunable nanowire nonlinear optical probe

One crucial challenge for subwavelength optics has been thedevelopment of a tunable source of coherent laser radiation for use inthe physical, information, and biological sciences that is stable at roomtemperature and physiological conditions. Current advanced near-fieldimaging techniques using fiber-optic scattering probes1,2 have alreadyachieved spatial resolution down to the 20-nm range. Recently reportedfar-field approaches for optical microscopy, including stimulatedemission depletion (STE… more

Date: February 18, 2008

Creator: Nakayama, Yuri; Pauzauskie, Peter J.; Radenovic, Aleksandra; Onorato, Robert M.; Saykally, Richard J.; Liphardt, Jan et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Echo-enabled Harmonic Generation Free Electron Laser

In this paper, we systematically study the echo-enabled harmonic generation (EEHG) free electron laser (FEL). The EEHG FEL uses two modulators in combination with two dispersion sections that allow to generate in the beam a high harmonic density modulation starting with a relatively small initial energy modulation of the beam. After presenting analytical theory of the phenomenon, we address several practically important issues, such as the effect of incoherent synchrotron radiation in the dispe… more

Date: December 18, 2008

Creator: Xiang, D. & Stupakov, G.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Ultrafast dynamics of strong-field dissociative ionization ofCH2Br2 probed by femtosecond soft x-ray transient absorption spectroscopy

Femtosecond time-resolved soft x-ray transient absorption spectroscopy based on a high-order harmonic generation source is used to investigate the dissociative ionization of CH{sub 2}Br{sub 2} induced by 800 nm strong-field irradiation. At moderate peak intensities (2.0 x 10{sup 14} W/cm{sup 2}), strong-field ionization is accompanied by ultrafast C-Br bond dissociation, producing both neutral Br ({sup 2}P{sub 3/2}) and Br* ({sup 2}P{sub 1/2}) atoms together with the CH{sub 2}Br{sup +} fragment… more

Date: January 15, 2008

Creator: Loh, Zhi-Heng & Leone, Stephen R.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Organic materials for second harmonic generation. Final report

Materials were chosen by screening the Cambridge Crystallographic Index for new noncentrosymmetric crystalline compounds, by screening commercially available materials or by synthesis of unique new substances. Measurements were then made on the powder form of these materials. Langmuir-Blodgett films were deposited and studied. In addition to the above studies, a computer program was developed to calculate (hyper) polarizabilities of organic molecules and thus aid in the selection of materials f… more

Date: March 31, 1985

Creator: Twieg, R.J. (comp.)

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Basic Considerations on Surface Optical Nonlinearities

The origins of the surface nonlinearity in surface second harmonic generation are discussed. It is shown that this second-order nonlinear optical process is characterized by a surface nonlinear susceptibility tensor containing both local and nonlocal contributions.

Date: January 1, 1986

Creator: Guyot-Sionnest, P.; Chen, W. & Shen, Y.R.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Prospects for the FEL (Free Electron Laser)

The future for FELs depends upon the very large number of applications which is envisioned for them. These grow out of the FEL extensive range of wavelengths, tunability, and high power capability. High power requires demonstration of optical guiding. Tunability has already been demonstrated. And the effort to extend the range of wavelengths is ever ongoing. The future will also bring more work on gas-loaded FELs, on electromagnetic wigglers, and on harmonic generation. We can, also, look forwa… more

Date: April 1, 1989

Creator: Sessler, Andrew M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Nova performance at ultra high fluence levels

Nova is a ten beam high power Nd:glass laser used for interial confinement fusion research. It was operated in the high power high energy regime following the completion of construction in December 1984. During this period several interesting nonlinear optical phenomena were observed. These phenomena are discussed in the text. 11 refs., 5 figs.

Date: January 1, 1986

Creator: Hunt, J. T.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Tandem Mirror Experiment Upgrade (TMX-U) overview-recent events

Since its construction and commissioning was completed in the winter of 1981, the Tandem Mirror Experiment Upgrade (TMX-U) has been conducting tandem mirror thermal barrier experiments. The work, following the fall of 1983 when strong plugging with thermal barriers was achieved, has been directed toward controlling radial transport and forming thermal barriers with high density and Beta. This paper describes the overall engineering component of these efforts. Major changes to the machine have i… more

Date: November 14, 1985

Creator: Calderon, M.O. & Bell, H.H.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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A superconducting short period undulator for a harmonic generation FEL experiment

A three stage superconducting (SC) undulator for a high gain harmonic generation (HGE) FEL experiment in the infrared is under construction at the NSLS in collaboration with Grumman Corporation. A novel undulator technology suitable for short period (6--40mm) undulators will be employed for all three stages, the modulator, the dispersive section and the radiator. The undulator triples the frequency of a 10.4[mu]m CO[sub 2] seed laser. So far a 27 period (one third of the final radiator) prototy… more

Date: January 1, 1993

Creator: Ingold, G.; Solomon, L.; Ben-Zvi, Ilan; Krinsky, S.; Li, D.; Lynch, D. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Nonlinear relativistic interaction of an ultrashort laser pulse with a cold plasma

We investigate the nonlinear, relativistic dynamics that result when intense (10{sup 18}W/cm{sup 2} and above) and ultrashort (one plasma period or shorter) laser pulse travels through a cold underdense plasma. Using a Lagrangian analysis of the plasma response, it can be demonstrated that the nonlinear wake, the collective dissipation, the nonlinear Compton losses, and the harmonic generation, are all determined by a finite set of integrated scalar quantities. This result holds for one-dimensi… more

Date: January 1, 1992

Creator: Rax, J. M. & Fisch, N. J.

Item Type: Report

Partner: UNT Libraries Government Documents Department