Modelocked femtosecond lasers require of luminescent ions with large emission bandwidth and tunability. This requirement is difficult to fulfill with lanthanides due to the inner nature of the 4f orbital. The concept of «disordered single crystals» which  is based on multiple (isovalent or heterovalent) cationic substitutions on the same lattice site has gained attention to solve the problem but results are still limited. In our recent publication in Journal of Alloys and Compounds 961 (2023) 171092 (doi 10.1016/j.jallcom.2023.171092) we show that the random orientation of the Bi3+ non-bonded 6s2 lone pair induces a large band broadening of the Yb3+ emission in monoclinic KY1-x-yBixYby(WO4)2 single crystals. The  growth of these crystals and their laser capabilities are demonstrated within the activity of our THINLAS project.

 

 

 

Most common thermometric luminescent  nanoprobres contain alkaline and/or halogen ions which poisson currently used catalysts, for instance the well known NaYF4 host based compounds. Our IMPETUSS project (PID2021-128090OB-C21) aims the development of eficient luminescence nanoprobes compatible with standardly catalyzed reactions. In this direction we develloped alkaline and halogen-free β´Gd2(MoO4)2 nanoprobes doped with Yb3+, Er3+ and Tm3+. We defined three different ratiometric  channels to determine  temperature from 20 to 600ºC with optimised sensitivity. See Journal of Alloys and Compounds 913 (2022) 165180 doi 10.1016/j.jallcom.2022.165180.

 

Our recent publication in Journal of Materials Chemistry A 2023, 11, 19854 (doi 10.1039/d3ta03654e) in collaboration with the Institute of Chemical Technology (UPV-CSIC) in Valencia (among others) adresses the problem found in Tandem Catalysis of having»spatially proximate but thermally distant» catalysts contained in a single reactor.  An elegant solution arose through the specific heating of the hot catalyst by magnetic susception. A thermal gradient of 50 ºC between the hot and cold catalysts was infered by  luminescence lifetime thermometry by using Eu3+-doped and Cr3+-doped nanoprobes. A probe of concept was demostrated by direct production of propene from ethene, via sequential olefin dimerization and metathesis reactions.

In February 2024 Dr. Xiumei Han incorporated to the REALM group as responsible of the Top Seeded Solution Crystal Growth laboratory.

Also in February 2024  Illán Calvo Llorente  incorporated to the REAL group  hired by THINLAS project.

We wish both of you all success during your stays.

 

“Non-conventional solutions on luminescence-based high temperature thermometry for applications of industrial interest (IMPETUSS)” Project has been awarded for the period 01/09/2022 to 31/08/2025.

This project proposes new strategies for the design of contactless photoluminescence (PL) thermal probes spanning their operation range to temperatures well above 300 K. These probes will be based either on the PL of lanthanides (Ln) incorporated in inert refractory hosts or on that of carbon quantum dots (CQDs). In combination with remote reading techniques, the new developed thermal probes will enable the creation of bidimensional temperature maps, which may prevent device failures by allowing early detection of thermally aged areas.

“Valorisation of CaNbGa garnets as thin disk elements in high power, high-rate, ultrashort pulsed laser oscillators (THINLAS)” project has been granted for the period 01/12/2022 to 30/11/2024.

This Project aims the extension of thin disk laser (TDL) technology, based on Yb doped YAG single crystals, to modelocked operation by using disordered single crystal Ca₃(NbGa)₅O₁₂ garnets (CNGG) doped with Yb (or Tm, Ho, and Tm+Ho for emission in the λ≈ 2 µm region), to provide laser pulse durations in the femtosecond (1 fs= 10^-15 s) time scale with large pulse peak powers. This is based on the large Yb³⁺ bandwidth in previously developed CNGG crystals, typically FWHM= 23.5 nm (or 221 cm^-1), along with an optical absorption three times more efficient than in YAG, which promises thinner disks with better cooling. The productivity of laser material processing and monitoring in various fields will be greatly improved by a laser module with the characteristics described above. Just to mention some few examples: In photovoltaic silicon cell processing for CO2-free energy harvesting, surface texture free of chemical wastes will be possible. Polymeric soft transparent materials, extensively used in biomedical health care, can be welded and mechanically processed with λ≈ 2 µm laser equipment. LIDAR systems incorporating increased high power lasers and repetition rates will have longer penetration depths and better spatial resolution. Overall, the development of high power–high repletion rate lasers with ultrashort pulse duration will provide new tools for improving the wellness of the population through routes that are compatible with a sustainable and green manufacturing.

On July 14th 2021 Jorge Omar Álvarez Pérez obtained his PhD degree from the Autonomous University of Madrid  with the work entitled «Caracterización física y láser de monocristales de granates desordenados tipo Ca3(NbGa)5O12 dopados con Yb3+»  (Physical and laser characterization of Ca3(NbGa)5O12 disordered single crystals doped with Yb3+). The work was awared with the «cum laude» maximum qualificatlon.

The work “A roadmap for laser optimization of Yb:Ca₃(NbGa)₅O₁₂–CNGG–type single crystal garnet”  published  in Journal of Materials Chemistry C vol 9, pgs 4628-4642, 2021 https://pubs.rsc.org/en/Content/ArticleLanding/2021/TC/D0TC05718E#!divAbstract

completes a trilogy of new physical knowledge and laser performance progress of this disordered cubic crystal garnet with applications in ultrashort laser pulse oscillators.

Following the path of our original proposal of CNGG Na+ modification for charge compensation of Yb3+ doping, in a first work we introduced a crystallographic model to describe the Yb3+ optical bandwidth. In a second work we disclosed the presence of a small amount of Yb3+ in centrosymmetric octahedral position with dominant magnetic dipole transitions. In the present work we describe how to minimize the crystal coloration,  the limits for Na incorporation and the relevant parameters helping for laser performance optimization.

Na and Li codoping of Yb:CNGG is found to provide the broadest tuning range along with best laser preformances.