R. Moncorge

Room temperature cw laser action of Y2SiO5:Yb3+, Er3+ at 1.57 μm

Abstract For the first time is reported room temperature cw laser action of a Yb3+, Er3+-doped orthosilicate Y2SiO5 single crystal at about 1.57 μm. Comparison is made with the Yb3+, Er3+-doped phosphate glass Kigre QE-7S.

Spectroscopy and laser operation of Pr, Mg:SrAl12O19

Pr3+‐doped SrAl12O19 has been investigated spectroscopically as a visible laser material. Its 3P0 fluorescence lifetime is rather long for an oxide, about 35 μs. This excited state exhibits only mild concentration and temperature quenching, so that concentrations high enough to give good ground state absorption into the 3P0 and 3P1 manifolds still give strong, long‐lived emission. The ground state absorption spectra indicate that excited state absorption into the 4f5d configuration is less likely to be significant at laser wavelengths in this host than in Y3Al5O12. The stimulated emission cross sections of major emission lines have been estimated, and are quite realistic for laser operation. Laser pumped laser operation has been demonstrated in the red (3P0→3F2) at room temperature and in the blue‐green (3P0→3H4) at cryogenic temperatures.

Excited-state absorption and energy transfer in Er3+ doped LiYF4

Abstract Here is reported the first of a series of optical studies which should end in a complete comprehension of the luminescence mechanisms in the laser material LiYF 4 activated by Ho 3+ and sensitized by Er 3+ and Tm 3+ ions, i.e. αβLiYF 4 :Ho 3+ , with a view to optimizing its characteristic infrared emission in the 2 μm region at room temperature. The Er 3+ ion is the most important sensitizer; thus it is of prime interest to know its internal characteristics. The present work eludidates the dominating optical processes in the systems LiYF 4 :1%Er 3+ and LiErF 4 . They are described in terms of rate equations, the initial conditions of which directly reflect the various possible excitations in the visible as well as in the infrared regions.

Efficient and stable pulsed laser operation of Ce:LiLuF4 around 308 nm

Abstract Very efficient and stable laser operation of Ce 3+ -doped LiLuF 4 (Ce:LLF) single crystals longitudinally pumped with a Ce:LiSAF pulsed laser is demonstrated for the first time. At the peak operating wavelength of 308 nm, laser thresholds as low as 250 mJ cm −2 and laser slope efficiencies and output energies as high as 55% and 2 mJ, respectively, have been obtained at a pulse repetition rate of 20 Hz.

ROOM-TEMPERATURE DIODE-PUMPED CONTINUOUS-WAVE SRY4(SIO4)3O:YB3+, ER3+ CRYSTAL LASER AT 1554 NM

Continuous‐wave (cw) laser operation at room temperature of an Yb3+, Er3+ doped oxyapatite single crystal SrY4(SiO4)3O pumped at 980 nm by an InGaAs diode laser has been achieved around the eye‐safe laser wavelength of 1554 nm.

Temperature dependent luminescence of Bi4Ge3O12 · discussion of possible models

Abstract Absorption, emission, excitation and decay time measurements have been made on a single crystal of Bi 4 Ge 3 O 12 at different temperatures from 4 to 300 K. A sharp increase in the fluorescence lifetimes is observed below 10 K. From these experimental results we try to identify the nature of the absorbing and emitting centers by using different models coming from MO considerations on the (GeO 4 ) 4- , (BiO 6 ) 9- and Bi(GeO 4 ) 21- 6 clusters, then assuming an excitonic process. The last assumption seems to be the most probable.

Spectroscopic investigation and two-micron laser performance of Tm3+:CaYAlO4 single crystals

Tm3+ doped single crystals of CaYAlO4 have been grown and studied. A complete spectroscopic analysis has been performed to examine the laser potentials of the main Tm3+ emission transitions in this material and room temperature continuous-wave (CW) laser operation of a 2% Tm3+ doped sample pumped at 795 nm by a Ti:sapphire laser has been achieved around 1970 nm.

Luminescence properties of the Tm3+ doped silicates Y2SiO5, CaY4(SiO4)3O and SrY4(SiO4)3O

Abstract The optical properties of powders and crystals of Tm 3+ doped silicates of formula Y 2 SiO 5 , CaY 4 (SiO 4 )O and SrY 4 (SiO 4 )O are presented. These materials emit very interesting infrared fluorescences around 2 μm which make them very efficient room temperature laser systems when pumped by diode lasers around 795 nm. The spectral and dynamical behaviour of these fluorescences in the three compounds is first analysed as a function of the temperature and of the topant concentration. Then a more detail study of the infrared and visible fluorescences in Tm 3+ doped Y 2 SiO 5 is developed, including a Judd-Ofelt analysis of the absorption spectra and an analysis of the main energy transfer and multiphonon relaxation processes.

Electron‐spin resonance and fluorescence investigation of LaMgAl11O19:Ti3+, a potential tunable laser material

Single crystals of LaMgAl11O19:Ti (LMA:Ti) have been grown from the melt by the Verneuil (flame fusion) process. As‐grown crystals contain titanium in both 3+ and 4+ oxidation states. Ti4+ ions can be reduced into the 3+ state by annealing at 1200 °C under hydrogen atmosphere. The crystals exhibit a broadband fluorescence extending from ∼600 to 1200 nm and peaking around 775 nm. The fluorescence lifetime is found to be ∼6 μs at 10 K against ∼4 μs at 300 K; it does not depend significantly on the emission wavelength, this indicating that fluorescence originates mainly from one type of Ti3+ active ions. Electron‐spin‐resonance (ESR) investigations reveal that Ti3+ ions are distributed among the three octahedral sites of the magnetoplumbite structure of the host, with a marked predominance for the regular octahedral site (2a), which contains about 90% of the titanium detected by ESR. Crystal field splitting of the t2g level has been estimated for the three sites and it is proposed that Ti3+ in the (12k) site...

Spectroscopic properties and fluorescence dynamics of Er3+ and Yb3+ in CaYAlO4

Abstract The optical properties of Er 3+ - and (Er 3+ , Yb 3+ )-doped CaYAlO 4 single crystals grown by the Czochralski technique are presented. These crystals emit infrared fluorescence in the eye-safe spectral region around 1.55 μm. The measured electric dipole oscillator strengths of the transitions between the J manifolds at 300 K are compared with those derived from the Judd-Ofelt theory. The non-radiative relaxation rates from the various excited states are determined by calculating the difference between the measured fluorescence decay rates and the calculated radiative transition rates. The stimulated emission cross sections are determined from the absorption spectra with the aid of the reciprocity method. The properties of the (Er 3+ , Yb 3+ )-doped CaYAlO 4 single crystals are compared with those of the well-known phosphate glass.