Publications by Simon Hooker


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/cm 2 . 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 LiLuF 4 :Ce 3+ , 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 LiYF 4 :Nd 3+ and LaF 3 :Nd 3+ .


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 F 2 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′ 2 Δ-B 2 II(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’ 2 Δ-X 2 n (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’ 2 Δ-X 2 n (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

S HOOKER, C 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

S HOOKER, C 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.


Proposed vacuum ultraviolet laser in nitric oxide

(1989) 112-113

SM Hooker, CE Webb

An optically pumped laser that operates in the VUV region of the spectrum with pulse energies in the millijoule range is proposed. The laser is expected to oscillate on ten to 13 new laser lines between 158 and 250 n. The transmission of the F 2 pump laser output was measured as a function of NO pressure to deduce the absorption cross section. The absorption was also modeled using spectral rate equations. The model reproduces the observed transmission very well and predicts that the broadening of the absorption line is due to rapid quenching of the upper level. The measurements are not consistent with the results reported by T.J. McKee The predicted upper level population is of the order of 8 × 10 14 cm -3 for an NO pressure of 800 mbar, which would give a small signal gain of ≈ 1 cm -1 for the strongest line. On the basis of this it appears to be possible to realize the proposed laser.


Generation of laser pulse trains for tests of multi-pulse laser wakefield acceleration

Nuclear Instruments and Methods in Physics Research A (0)

SM Hooker, L Corner, C Arran, J Cowley, G Cheung, C Thornton, R Walczak

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