"Mixed" Tm:Ca(Gd,Lu)AlO4 - a novel crystal for tunable and mode-locked 2 µm lasers.

We report on the crystal growth, spectroscopy characterization and first laser operation of a new tetragonal disordered "mixed" calcium aluminate crystal, Tm:Ca(Gd,Lu)AlO4. The introduction of Lu3+ leads to an additional inhomogeneous broadening of Tm3+ absorption and emission spectra compared to the well-known Tm:CaGdAlO4. The maximum stimulated-emission cross-section for the 3F4 → 3H6 Tm3+ transition is 0.91 × 10-20 cm2 at 1813 nm for σ-polarization, and the emission bandwidth is more than 200 nm. A continuous-wave diode-pumped Tm:Ca(Gd,Lu)AlO4 laser generates 1.82 W at 1945 nm with a slope efficiency of 29%. Under Ti:Sapphire laser pumping, a continuous tuning of the laser wavelength from 1836 to 2083 nm (tuning range: 247 nm) is demonstrated. The Tm:Ca(Gd,Lu)AlO4 crystal is promising for tunable/femtosecond lasers at ~2 μm.

[1]  B. Aull,et al.  Vibronic interactions in Nd:YAG resulting in nonreciprocity of absorption and stimulated emission cross sections , 1982 .

[2]  D. Shen,et al.  Highly efficient Tm:CaYAlO4 laser in-band pumped by a Raman fiber laser at 1.7  μm. , 2016, Applied optics.

[3]  Xiaodong Xu,et al.  Growth and spectra properties of Tm, Ho doped and Tm, Ho co-doped CaGdAlO4 crystals , 2014 .

[4]  Xiaodong Xu,et al.  Passively Q-Switched Tm:CaGdAlO_4 laser using a Cr^2+:ZnSe saturable absorber , 2017 .

[5]  Günter Huber,et al.  175 fs Tm:Lu2O3 laser at 2.07 µm mode-locked using single-walled carbon nanotubes. , 2012, Optics express.

[6]  Klaus Petermann,et al.  Model for the calculation of radiation trapping and description of the pinhole method. , 2007, Optics letters.

[7]  Patrick Georges,et al.  Magic mode switching in Yb:CaGdAlO4 laser under high pump power. , 2013, Optics letters.

[8]  M. Tonelli,et al.  Crystal growth and spectral broadening of a promising Yb:CaLuxGd1−xAlO4disordered crystal for ultrafast laser application , 2017 .

[9]  Jun Xu,et al.  Sellmeier equations, group velocity dispersion, and thermo-optic dispersion formulas for CaLnAlO4 (Ln = Y, Gd) laser host crystals. , 2017, Optics letters.

[10]  Ge Zhang,et al.  Sub-100  fs Tm:MgWO4 laser at 2017  nm mode locked by a graphene saturable absorber. , 2017, Optics letters.

[11]  J. Didierjean,et al.  47-fs diode-pumped Yb3+:CaGdAlO4 laser. , 2006, Optics letters.

[12]  Bahram Zandi,et al.  Spectroscopic evaluation of CaYA1O4 doped with trivalent Er, Tm, Yb and Ho for eyesafe laser applications , 1994 .

[13]  Xing Wu,et al.  Study of single-crystal growth of Tm3+: CaYAlO4 by the floating-zone method , 2000 .

[14]  C. O. Paiva-santos,et al.  Structural, electronic and photoluminescence properties of Eu3+-doped CaYAlO4 obtained by using citric acid complexes as precursors , 2016 .

[15]  B. Judd,et al.  OPTICAL ABSORPTION INTENSITIES OF RARE-EARTH IONS , 1962 .

[16]  G. S. Ofelt.  Intensities of Crystal Spectra of Rare‐Earth Ions , 1962 .

[17]  Yongguang Zhao,et al.  Sub-10 optical-cycle passively mode-locked Tm:(Lu2/3Sc1/3)2O3 ceramic laser at 2 µm. , 2018, Optics express.

[18]  Xavier Mateos,et al.  Vibronic thulium laser at 2131 nm Q-switched by single-walled carbon nanotubes , 2016 .

[19]  A. V. Mandrik,et al.  Integral Method o Reciprocity in the Spectroscopy of Laser Crystals with Impurity Centers , 2004 .

[20]  P. Georges,et al.  32-fs Kerr-lens mode-locked Yb:CaGdAlO₄ oscillator optically pumped by a bright fiber laser. , 2014, Optics letters.

[21]  Johan Petit,et al.  Laser emission with low quantum defect in Yb: CaGdAlO4. , 2005, Optics letters.

[22]  Liejia Qian,et al.  Spectroscopic characteristics and laser performance of Tm:CaYAlO4 crystal , 2013 .

[23]  Norman P. Barnes,et al.  Branching ratios, cross sections, and radiative lifetimes of rare earth ions in solids: Application to Tm3+ and Ho3+ ions in LiYF4 , 1998 .

[24]  R. Stoneman,et al.  Efficient, broadly tunable, laser-pumped Tm:YAG and Tm:YSGG cw lasers. , 1990, Optics letters.

[25]  Xiaodong Xu,et al.  High-Power CW and Q-Switched Tm:CaYAlO4 Lasers at $1.94~\mu \text{m}$ for Shallow Water Absorption , 2017, IEEE Photonics Technology Letters.

[26]  Patrick Georges,et al.  Thermo-optic characterization of Yb:CaGdAlO 4 laser crystal , 2014 .

[27]  Johan Petit,et al.  Inhomogeneous broadening of optical transitions in Yb:CaYAlO4 , 2008 .

[28]  Xavier Mateos,et al.  SESAM mode-locked Tm:CALGO laser at 2 µm , 2016 .

[29]  M. A. Ivanov,et al.  Hypersensitive transitions of Tm3+, Ho3+ and Dy3+ rare-earth ions in garnet crystals , 2012 .

[30]  G. Xie,et al.  Dual-wavelength synchronous operation of a mode-locked 2-μm Tm:CaYAlO4 laser. , 2015, Optics letters.

[31]  Nicolas Garnier,et al.  Spectroscopic investigation and two-micron laser performance of Tm3+:CaYAlO4 single crystals , 1997 .

[32]  Yongguang Zhao,et al.  78  fs SWCNT-SA mode-locked Tm:CLNGG disordered garnet crystal laser at 2017  nm. , 2018, Optics letters.

[33]  M. Pollnau,et al.  Thulium channel waveguide laser with 1.6 W of output power and ∼80% slope efficiency. , 2014, Optics letters.