Transcript Nessun titolo diapositiva - INFN

ULTRAVIOLET SOLID STATE LASER SOURCES
a,
a
Toci ,
a
D. Alderighi ,
b,A.
c
Piegari
M. Vannini G.
M. Tonelli
(a) IFAC-CNR, Firenze; (b) Physics Dept., Pisa University; (c) ENEA-Casaccia Research Center, Roma
Corresponding author: M. Vannini, IFAC-CNR, V. Madonna del Piano 50019 Sesto F.no, Firenze. E-mail: [email protected]
Scientific targets
Proposer and coordinator
Study 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:
Ist. di Fisica Applicata “Carrara” IFAC-CNR, Firenze
Project Coordinator: Dr. Matteo Vannini
Design and development of Ce:LiCAF and Ce:LiLuF laser
prototypes
Partners
Physics Dept., Pisa University - Prof. Mauro Tonelli
Growth of Ce:LiLuF and other experimental crystals
with Ce doping
ENEA, Optical Components group - Dr. Angela Piegari
“Casaccia” Research Center, Roma
Development 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
Application fields
0.6
1000
0.4
500
0.2
0
220
240
260
280
Wavelength (nm)
300
0.0
320
0
Short-pulse gas discharge flashlamps filled with Xe at subatmospheric
pressure are currently under development.
When excited with submicrosecond current pulses, Xe exhibits a spectrum
with 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
1.0
0.8
Ce:LiCaAlF6
0.8
0.6
0.6
0.4
0.4
266 nm
0.2
0.2
0.0
0.0
200
225
250
275
1.0
1.0
300
325
0.6
0.4
248 nm
0.2
0.0
350
240
Wavelength (nm)
Tunability:
Upper level life time:
Saturation fluence:
0.8
Ce:LiLuF4
Fluorescence (a.u.)
1500
Ce-doped laser media
Absorption (a.u.)
0.8
Life sciences: systems for fluorescence diagnostics, with tunable excitation
Fluorescence (a.u.)
2000
Medical : 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
Absorption (a.u.)
1.0
Absorption (a.u.)
Power spectral density (a.u.)
First results - Xe flashlamps
2500
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
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
260
280
300
320
340
360
Wavelength (nm)
Tunability:
305-340 nm
Upper level life time:39 ns
Saturation fluence: 50 mJ/cm2 @ 325
nm
280-330 nm
30 ns
115 mJ/cm2
Allows optical pumping at 266 nm and
261.75 nm (Nd:YAG or Nd:YLF IV harmonic)
Allows optical pumping at 248 nm(KrF
excimer laser)
Preliminary results - Laser pumping
Output coupler,
flat, R=60%
Superstable cavity
without spectral
selection
E1 mJ
t=4.6 ns FWHM
End mirror, r =200 cm
R=100% @ 290 nm,
T=85% @ 266 nm
Pump beam
E10 mJ, t=5 ns
Ce:LiCAF
f=60 cm
17 cm
Fluence at the crystal surface  0.8 J/cm2
Tunable cavity
Quartz prism,
Max output energy. 200 J @ 289 nm Brewster/Brewster
Tuning range : 283.8 nm - 291.0 nm
19
cm
Linewidth  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
Output coupler,
flat, R=60%
E0.2 mJ
Ce:Licaf
End mirror, flat
R=100% @ 290 nm,
T=85% @ 266 nm
f=60 cm
Pump beam
(Ep=5.8 mJ)