Publications by Simon Hooker


Inner-shell soft X-ray lasers in Ne-like ions driven by optical field ionization

Optics Communications 182 (2000) 209-219

SM Hooker

A novel short-wavelength laser based upon monopole excitation of inner-shell electrons in Ne-like ions following optical field ionization with circularly polarized radiation is discussed. Calculations of the small-signal gain are presented for one such ion, Ne-like Ar, for which a small-signal gain of 13.7 cm-1is predicted on the 2s → 2p hole transition at 15.8 nm for an Ar pressure of 50 mbar. Extensions of this approach to other inner-shell transitions are suggested. © 2000 Elsevier Science B.V. All rights reserved.


Simulations of the propagation of high-intensity laser pulses in discharge-ablated capillary waveguides

Pacific Rim Conference on Lasers and Electro-Optics, CLEO - Technical Digest (2000) 293-294

DJ Spence, SM Hooker

An overview is given on the results of numerical simulations of the propagation of high-intensity pules through discharge-ablated capillary waveguides. The numerical code solves the paraxial wave equation for a plasma undergoing optical field ionization, and so accounts for refractive defocusing due to further ionization by the propagating pulse.


Inner-shell soft x-ray lasers driven by optical field ionization

Pacific Rim Conference on Lasers and Electro-Optics, CLEO - Technical Digest (2000) 515-516

SM Hooker

Presented is a novel approach for driving short-wavelength lasers, with good prospects for scaling to shorter wavelengths. Present investigations include analysis of extensions to other transitions such as the 3s → 3p and 3p → 3d hole transitions in Ni-like ions following monopole excitation of 3s and 3p holes in OFI plasmas. The results of those calculations are presented.


Measurement of the electron-density profile in a discharge-ablated capillary waveguide

Optics Letters 24 (1999) 993-995

DJ Spence, PDS Burnett, SM Hooker

Discharged-ablated capillary waveguides were investigated based on electron-density profile using time-resolved interferometric measurements. A pronounced axial minimum with a relative depth of as much as 60% of the axial electron density was developed in the electron density profile. Results showed that this profile can be used for high-intensity laser pulse tunneling.


Effects of a prepulse in the femtosecond-pulse-driven Xe IX laser

Journal of the Optical Society of America B: Optical Physics 14 (1997) 2735-2741

SM Hooker, PT Epp, GY Yin

We describe experiments that demonstrate the detrimental effect of a prepulse on the femtosecond-pulse-driven Xe IX laser. The mechanism of this effect is discussed in terms of the results of a hydrodynamic model of the preplasma formed by the prepulse. The benefit of inserting a simple electro-optic switch that allows full transmission of the main driving pulse, but reduces the prepulse to a level at which no preplasma is formed, is demonstrated experimentally. © 1997 Optical Society of America.


Vacuum ultraviolet gain measurements in optically pumped LiYF<inf>4</inf>:Nd<sup>3+</sup>

Applied Physics B: Lasers and Optics 64 (1997) 293-300

JS Cashmore, SM Hooker, CE Webb

We present measurements of the net-induced gain on the 5d-4f transition at 186 nm in LiYF4:Nd3+optically pumped by radiation from a molecular fluorine laser. It is found that for LiYF4: Nd3+one of a series of potential continuously tunable VUV lasers, relatively strong excited-state absorption results in net-induced loss. The prospects for VUV laser operation being realised in other rare-earth-doped fluorides is discussed.


Light at the end of the tunnel? Femtosecond pulses excite short-wavelength lasers

Optics and Photonics News 8 (1997) 21-25

SM Hooker

Hooker explores current work in the XUV and soft x-ray spectral region aimed at achieving "table-top" short-wavelength lasers.


FEMTOSECOND-PULSE-DRIVEN ELECTRON-EXCITED EXTREME-ULTRAVIOLET LASERS IN BE-LIKE IONS

OPTICS LETTERS 20 (1995) 1994-1996

SM HOOKER, SE HARRIS


Laser ablation of polymeric materials at 157 nm

Journal of Applied Physics 77 (1995) 2343-2350

A Costela, I García-Moreno, F Florido, JM Figuera, R Sastre, SM Hooker, JS Cashmore, CE Webb

Results are presented on the ablation by 157 nm laser radiation of polytetrafluoroethylene (PTFE), polyimide, polyhydroxybutyrate (PHB), poly(methyl methacrylate) (PMMA), and poly(2-hydroxyethyl methacrylate) with 1% of ethylene glycol dimethacrylate as a crosslinking monomer. Direct photoetching of PHB and undoped PTFE is demonstrated for laser fluences ranging from 0.05 to 0.8 J/cm2. The dependence of the ablation process on the polymer structure is analyzed, and insight into the ablation mechanism is gained from an analysis of the data using Beer-Lambert's law and the kinetic model of the moving interface. Consideration of the absorbed energy density required to initiate significant ablation suggests that the photoetching mechanism is similar for all the polymers studied. © 1995 American Institute of Physics.


MEASUREMENTS OF TRANSIENT GAIN AND LOSS IN SOLID STATE VUV LASER MATERIALS

(1994) 295-296

SM HOOKER, JS CASHMORE, CE WEBB


Progress in vacuum ultraviolet lasers

Progress in Quantum Electronics 18 (1994) 227-274

SM Hooker, CE Webb


Transient gain/loss in tunable solid-state vacuum ultraviolet laser media

Conference on Lasers and Electro-Optics Europe - Technical Digest (1994) 1-2

JS Cashmore, SM Hooker, CE Webb

We have developed a model for the net induced gain as a function of pump fluence, based on a rate equation analysis of the populations of the 4f(n-1) 5d → 4f(n) level of the activator ions and of absorptive color centers. As an example, this has been applied to LiLuF4:Ce3+, in which we have also observed laser oscillation at 326.9 nm. The net gain is seen to rise rapidly with pump fluence before showing saturation and roll-off. This behavior can be explained by the creation of color centers that absorb strongly in the UV. We will present the results of similar measurements in the VUV on samples of LiYF4:Nd3+ and LaF3:Nd3+.


SOLID-STATE VUV LASERS

(1993) 740-741

SM HOOKER, JS CASHMORE, CE WEBB


OBSERVATION OF VACUUM ULTRAVIOLET-LASER OSCILLATION IN NITRIC-OXIDE

APPLIED OPTICS 32 (1993) 2062-2065

AM HAXELL, SM HOOKER, CE WEBB


Observation of new laser transitions and saturation effects in optically pumped NO

Applied Physics B Photophysics and Laser Chemistry 54 (1992) 119-125

SM Hooker, AM Haxell, CE Webb

We report investigations of an NO laser employing specially profiled magnetic fields of up to 3.4T, and F2 pump laser intensities as great as 20 MW cm-2. We have observed laser oscillation at 226 nm on a rotational branch of the B'-X/it(3-11) band of NO for the first time, in addition to the previously reported oscillation at 218 nm on the B'-X/it(3-10) band. We have also observed visible laser emission on a rotational branch of the B′2Δ-B2II(3-1) band of NO. Saturation of the NO laser pulse energy with pump intensity has been observed, the total NO laser pulse energy having been increased to 490 μJ. The possibility of increasing the NO laser pulse energy towards 1 mJ per transition is discussed. © 1992 Springer-Verlag.


Determination of the gain coefficient of an no iaser at 218 nm

Journal of Physics D: Applied Physics 25 (1992) 593-596

AM Haxell, SM Hooker, CE Webb

We have observed laser oscillation on the B’2Δ-X2n (3-10) and (3-11) transitions of an F2 laser pumped nitric oxide laser. The maximum total output pulse energy was 280μJ. We present here the results of an investigation to determine the maximum intra-cavity loss which still allows laser oscillation to occur in this system. This information has been used to find the effective gain coefficient of the NO laser, operating on the B’2Δ-X2n (3-10) transition at 218 nm by applying the condition for cw laser oscillation. The effective cw gain coefficient was found to be 0.25 cm-1 for pump laser intensities of 20 MWcrrr2. © 1992 IOP Publishing Ltd.


Influence of cavity configuration on the pulse energy of a high-pressure molecular fluorine laser

Applied Physics B Photophysics and Laser Chemistry 55 (1992) 54-59

SM Hooker, AM Haxell, CE Webb

We report an investigation of a high-pressure molecular fluorine laser operating at 158 nm. Several cavity configurations were studied, including one employing a roof prism as the high reflector. A maximum VUV pulse energy of 237 mJ, corresponding to a specific output of 3.3 J/1 was obtained when the laser was operated as a double-ended device. With single-ended operation the largest output energy was 176 mJ at a specific output of 2.5 J/1. © 1992 Springer-Verlag.


F2-PUMPED NO - LASER OSCILLATION AT 218NM AND PROSPECTS FOR NEW LASER TRANSITIONS IN THE 160-250NM REGION

IEEE JOURNAL OF QUANTUM ELECTRONICS 26 (1990) 1529-1535

SM HOOKER, CE WEBB


THE ABSORPTION OF 158-NM RADIATION IN NITRIC-OXIDE - THE PROSPECTS FOR AN OPTICALLY PUMPED VACUUM ULTRAVIOLET-LASER

APPLIED PHYSICS B-PHOTOPHYSICS AND LASER CHEMISTRY 51 (1990) 127-131

SM HOOKER, CE WEBB


Observation of laser oscillation in nitric oxide at 218 nm.

Opt Lett 15 (1990) 437-439

SM Hooker, CE Webb

We have recently proposed a scheme to produce coherent radiation at eight or more wavelengths between 158 and 242 nm by optically pumping a high-lying electronic level of nitric oxide. We report here the successful operation of this scheme to produce laser oscillation at 218 nm. The possibility of using this scheme to produce laser oscillation at other wavelengths is discussed.

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