Proposer and coordinatorIst. di Fisica Applicata “Carrara” IFAC-CNR, FirenzeProject Coordinator: Dr. Matteo VanniniDesign and development of Ce:LiCAF and Ce:LiLuF laser prototypes

Partners

Physics Dept., Pisa University - Prof. Mauro TonelliGrowth of Ce:LiLuF and other experimental crystals with Ce doping

ENEA, Optical Components group - Dr. Angela Piegari“Casaccia” Research Center, RomaDevelopment of optical components with multilayer coatings for UV lasers

Funding Fondo Speciale per lo Sviluppo della Ricerca di Interesse Strategico (Art. 51, comma 9, legge 27.12.1997 n.449) - Anno 2000

Ce-doped laser media

Tunability: 280-330 nm Upper level life time: 30 nsSaturation fluence: 115 mJ/cm2

Allows optical pumping at 266 nm and 261.75 nm (Nd:YAG or Nd:YLF IV harmonic)

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Ce:LiCaAlF6

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Ce:LiLuF4

Tunability: 305-340 nm Upper level life time:39 nsSaturation fluence: 50 mJ/cm2 @ 325 nm

Allows optical pumping at 248 nm(KrF excimer laser)

Application fieldsMedical : new compact UV laser sources for surgical applications, no longer requiring the use of toxic gases, such as the excimer lasers employed at present

Environmental: systems for the detection of atmospheric components such as SO2 and O3

Life sciences: systems for fluorescence diagnostics, with tunable excitation

Output coupler, flat, R=60%

End mirror, r =200 cmR=100% @ 290 nm, T=85% @ 266 nm

Ce:LiCAFf=60 cm

17 cm

Pump beam

E10 mJ, t=5 ns

E1 mJ t=4.6 ns FWHM

Fluence at the crystal surface 0.8 J/cm2

Superstable cavity without spectral selection

Tunable cavity

Output coupler, flat, R=60%

Ce:Licaf

f=60 cm19 cm

Pump beam (Ep=5.8 mJ)

E0.2 mJ

End mirror, flatR=100% @ 290 nm, T=85% @ 266 nm

3.5

cm

Quartz prism, Brewster/BrewsterMax output energy. 200 J @ 289

nmTuning range : 283.8 nm - 291.0 nmLinewidth 0.3 nm

Solid state laser system composed by :- Frequency doubled, diode pumped Nd:YLF laser- Fourth harmonic generation in BBO crystal- Ce:LiCAF laser oscillator

Preliminary results - Laser pumping

Scientific targetsStudy and development of new laser sources based on wide band gap crystal

with Cerium-ion doping, featuring tunable emission in the near UV.Two main research lines:

Development of all solid state devices with laser pumping (Nd:YAG or Nd:YLF laser fourth harmonic ), based on Ce:LiCaAlF6, tunable between 280-305 nm, and in particular: - Lasers with high pulse repetition rate (several kHz) and low pulse energy - Lasers with low pulse repetition rate (10-30 Hz), high pulse energy - Amplifier for ultrashort pulses (100 fsec) seeded from a Ti:Sapphire laser

Development of flashlamp-pumped lasers based on Ce:LiLuF4 at low pulse repetition rate, tunable between 305 and 340 nm. This aim needs the development of some pre-requisites:

- Innovative flashlamps, with short pulse duration and high UV emission

- Growth of high quality, large size Ce:LiLuF4 crystal rods

- Reflector with high UV efficiency for the lamp-crystal coupling

First results - Xe flashlamps

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Short-pulse gas discharge flashlamps filled with Xe at subatmospheric pressure are currently under development. When excited with submicrosecond current pulses, Xe exhibits a spectrumwith a substantial UV emission, and a fairly good matching with the absorption spectrum of Ce:LiLuF (see graph). At present, emission energies around 100 mJ and pulse durations of few hundreds of ns can be achieved. Other gases (Ar, XeBr excimer) are also under study

ULTRAVIOLET SOLID STATE LASER SOURCESM. Vannini a, G. Tocia, D. Alderighia, M. Tonelli b,A. Piegaric

(a) IFAC-CNR, Firenze; (b) Physics Dept., Pisa University; (c) ENEA-Casaccia Research Center, RomaCorresponding author: M. Vannini, IFAC-CNR, V. Madonna del Piano 50019 Sesto F.no, Firenze. E-mail: M.Vannini@ifac.cnr.it