In-Band Pumped Continuous-Wave Lasers Based on Ho:KY(WO₄)₂ Crystal and Ho:KGdYbY(WO₄)₂ Epitaxial Layer

2 μm lasers are in demand for a number of practical applications, such as environmental monitoring, remote sensing, medicine, material processing, and are also used as a pump sources for optical parametric generators. Crystals of double potassium tungstates doped with ions of rare-earth elements were shown to be promising materials both for  the  creation  of  classical  solid-state  lasers  and  waveguide  lasers. The aim of this work was to develop a tunable pump laser in the spectral region of 1.9 µm based on double tungstate crystals doped with thulium ions and to study the lasing characteristics of a Ho:KY(WO₄)₂ crystal and a Ho:KGdYbY(WO₄)₂ single-crystal epitaxial layer under in-band pumping.

With a Ho(1at.%):KY(WO₄)₂  crystal, continuous wave low-threshold lasing with an output power of 85 mW with a slope efficiency of 54 % at 2074 nm was achieved. For the first time to our knowledge, continuous wave laser  generation  in  a  waveguide  configuration  is  realized  in  a  single-crystal  layer of potassium tungstate doped with holmium ions grown by liquid-phase epitaxy. The maximum output power at a wavelength of 2055 nm was 16.5 mW.

1. Petrov V., Cinta Pujol M., Mateos X., Silvestre O., Rivier S., Aguilo M., Sole R.M., Liu J., Griebner U., Diaz F. Growth and properties of KLu(WO4)2, and novel ytterbium and thulium lasers based on this monoclinic crystalline host. Laser & Photonics Reviews, 2007, vol. 1, no. 2, pp. 179‒212. DOI: 10.1002/lpor.200710010

2. Kuleshov N.V., Lagatsky A.A., Podlipensky A.V., Mikhailov V.P., Huber G. Pulsed laser operation of Ybdoped KY(WO4)2 and KGd(WO4)2. Optics letters, 1997, vol. 22, no. 17, pp. 1317‒1319. DOI: 10.1364/OL.22.001317

3. Silvestre O., Pujol M.C., Rico M., Güell F., Aguiló M., Díaz F. Thulium doped monoclinic KLu(WO4)2 single crystals: growth and spectroscopy. Applied Physics B, 2007, vol. 87, no. 4, pp. 707‒716. DOI: 10.1007/s00340-007-2664-0

4. Batay L.E., Demidovich A.A., Kuzmin A.N., Titov A.N., Mond M., Kück S. Efficient tunable laser operation of diode-pumped Yb,Tm:KY(WO4)2 around 1.9 μm. Applied Physics B, 2002, vol. 75, pp. 457‒461. DOI: 10.1007/s00340-002-0998-1

5. Mateos X., Jambunathan V., Pujol M.C., Carvajal J.J., Díaz F., Aguiló M., Griebner U., Petrov V. CW lasing of Ho in KLu(WO4)2 in-band pumped by a diode-pumped Tm:KLu(WO4)2 laser. Optics Express, 2010, vol. 18, no. 20, pp. 20793‒20798. DOI: 10.1364/OE.18.020793

6. Jambunathan V., Mateos X., Loiko P.A., Serresa J.M., Griebner U., Petrov V., Yumashev K.V., Aguiló M., Díaza F. Growth, spectroscopy and laser operation of Ho:KY(WO4)2. Journal of Luminescence, 2016, vol. 179, pp. 50‒58. DOI: 10.1016/j.jlumin.2016.06.049

7. Jambunathan V., Mateos X., Pujol M.C., Carvajal J.J., Díaz F., Aguiló M., Griebner U., Petrov V. Continuous-wave laser generation at ~ 2.1 μm in Ho:KRE(WO4)2 (RE=Y, Gd, Lu) crystals: a comparative study. Optics Express, 2011, vol. 19, no. 25, pp. 25279‒25289. DOI: 10.1364/OE.19.025279

8. Mateos X., Loiko P., Lamrini S., Scholle K., Fuhrberg P., Vatnik S., Vedin I., Aguiló M., Díaz F., Griebner U., Petrov V. Power Scaling and ThermoOptics of Ho:KY(WO4)2 Thin-Disk Lasers: Effect of Ho3+ Concentration. Laser Congress 2017 (ASSL): OSA Technical Digest (online), 2017, p. AM3A.3. DOI: 10.1364/ASSL.2017.AM3A.3

9. Cattoor R., Manek-Hönninger I., Rytz D., Canioni L., Eichhorn M. Laser action along and near the optic axis of a holmium-doped KY(WO4)2 crystal. Optics Letters, 2014, vol. 39, no. 22, pp. 6407‒6410. DOI: 10.1364/OL.39.006407

10. Romanyuk Y.E., Borca C., Pollnau M., Rivier S., Petrov V. Yb-doped KY(WO4)2 planar waveguide laser. Optics letters, 2006, vol. 31, no. 1, pp. 53‒55. DOI: 10.1364/OL.31.000053

11. Van Dalfsen K., Aravazhi S., Grivas C., GarciaBlanco S.M.,Pollnau M.Thuliumchannelwaveguide laser with 1.6 W of output power and ~ 80 % slope efficiency Optics letters, 2014, vol. 39, no. 15, pp. 4380‒4383. DOI: 10.1364/OL.39.004380

12. Kifle E., Loiko P., Romero C., Rodríguez Vázquez de Aldana J., Ródenas A., Zakharov V., Veniaminov A., Aguiló M., Díaz F., Griebner U., Petrov V., Mateos X. Femtosecond-laser-written Ho:KGd(WO4)2 waveguide laser at 2.1 μm. Optics letters, 2019, vol. 44, no. 7, pp. 1738‒1741. DOI: 10.1364/OL.44.001738

13. Savikin A.P., Perunin I.Yu., Krashkin S.V., Budruev A.V., Grishin I.A. Anti-Stokes Luminescence in LiYF4:Ho3+, Yb3+ at 1.93 µm. Optics and Spectroscopy, 2018, vol. 124, pp. 307‒309. DOI: 10.1134/S0030400X18030190