Ivan Vedin

Efficient thin-disk Tm-laser operation based on Tm:KLu(WO 4 ) 2 /KLu(WO 4 ) 2 epitaxies

A diode-pumped thin-disk laser based on Tm:KLu(WO4)2/KLu(WO4)2 epitaxies is realized. The emission is in the 1850-1945 nm spectral range for Tm-doping between 5 and 15 at. %. The maximum slope efficiency of 47% with respect to the absorbed power obtained with 5 at. % Tm:KLu(WO4)2/KLu(WO4)2 corresponds to a maximum output power of ~6 W in cw operation.

Crystal growth, characterization and thin disk laser operation of KLu1−xTmx(WO4)2/KLu(WO4)2 epitaxial layers

Epitaxial samples of KLu1−xTmx(WO4)2/KLu(WO4)2 (x up to 0.15) have been obtained by the Liquid Phase Epitaxy (LPE) method. The lattice mismatch between the epitaxial layer and the substrate is small enough to allow the growth of good quality, well-oriented, single crystalline epilayers as evidenced by the 2θ scan of the (0k0) reflections and the rocking curve of the (040) reflection. Electron probe microanalysis shows an increase of 1021Tm3+ at cm−3 in a 2.5 μm interval at the substrate/layer interface. The main morphologies observed in the epilayers are steps and growth spirals. The laser operation around 2 μm, realized with epitaxial layers of 15 at% Tm doping and three different thicknesses, in a thin disk laser configuration with only two pump passes through the epitaxial layer, demonstrates maximum average output power as high as ∼1.4 W corresponding to a slope efficiency of 40%.

Highly efficient Ho:KY(WO4)2 thin-disk lasers at 2.06 µm

The recent advances in the development of Holmium monoclinic double tungstate thin-disk lasers are reviewed. The thin-disk is based on a 250-μm-thick 3 at. % Ho:KY(WO4)2 active layer grown on a (010)-oriented KY(WO4)2 substrate. When pumped by a Tm-fiber laser at 1960 nm with a single-bounce pump geometry, the continuous-wave Ho:KY(WO4)2 thin-disk laser generates an output power of 1.01 W at 2057 nm corresponding to a slope efficiency η of 60% and a laser threshold of only 0.15 W. The thin-disk laser is passively Q-switched with a GaSb-based quantum-well semiconductor saturable absorber mirror. In this regime, it generates an average output power of 0.551 W at ~2056 nm with η = 44%. The best pulse characteristics are 4.1 μJ / 201 ns at a repetition rate of 135 kHz. The laser performance, beam quality and thermo-optic aberrations of such lasers are strongly affected by the Ho3+ doping concentration. For the 3 at.% Ho3+-doped thin-disk, the thermal lens is negative (the sensitivity factors for the two principal meridional planes are -1.7 and -0.6 m-1/W) and astigmatic. The Ho:KY(WO4)2 epitaxial structures are promising as active elements in mode-locked thin-disk lasers at ~2060 nm.

Optical properties and high-efficiency lasing of Nd:YAG and Ho:YAG ceramics

We report on optical properties and high-efficiency lasing of YAG ceramics synthesized at IREE (Fryazino) and IEP (Ekaterinburg). The best slope efficiency is to be 36% for 1%Nd:YAG ceramics and 40% for 1%Ho:YAG ceramics, in the latter case the emission was centered at 2090 nm. Internal losses in domestic ceramics prove to be a few percents per centimeter.

High-efficiency thin-disk lasers based on Tm:KLu(WO 4 ) 2 crystals

We report on a high-efficiency room-temperature thin-disk lasers based on the monoclinic 5%Tm:KLuW crystals, epitaxial layers, and composite structures 5%Tm:KLuW/KLuW. The output spectra and oscillation performances of various types of thin-disk active elements are comparatively studied.

High-efficiency thin-disk laser based on Tm-doped KLu(WO 4 ) 2 /KLu(WO 4 ) 2 composite crystal

We report on a high-efficiency room-temperature 4.8%Tm:KLu(WO₄)₂/KLu(WO₄)₂ composite thin-disk laser. Continuous-wave output power as high as 4.6 W at 1840-1855 nm spectral band has been demonstrated, with optical and slope efficiencies being of 34 and 40%, respectively.

Efficient 2-μm laser oscillation of 5% Tm{sup 3+} : KLu(WO{sub 4}){sub 2} disks and 5% Tm{sup 3+} : KLu(WO{sub 4}){sub 2}/KLu(WO{sub 4}){sub 2} composite structures

The spectral and lasing characteristics of active disk elements made of double potassium – lutetium tungstates 5% Tm : KLuW and 5% Tm : KLuW/KLuW composite structures are comparatively studied. Laser power of about 5 W in the cw regime at a wavelength of 1.85 μm was achieved in a composite sample with the active layer thickness of 250 μm. Under quasi-cw pumping, the slope efficiency of all the studied samples exceeded 50%. It is experimentally shown that the internal stresses in the composite structures strongly affect the spectral characteristics of the laser radiation.

Power scaling of thin-disk Tm-lasers based on Tm:KLu(WO 4 ) 2 /KLu(WO 4 ) 2 epitaxy

Monoclinic double tungstate (DT) crystals, due to their maximum absorption and emission cross sections and minimum concentration quenching, seem ideal as hosts for thin-disk lasers with simplified geometry (number of pump passes). The first diode-pumped thulium thin-disk laser based on Tm:KY(WO4)2 generated CW output power of 4.9 W at 1950 nm using 4 pump passes [1]. The power handling capability of the thin-disk concept scales inversely proportional to the thickness and the high absorption of the monoclinic DTs reveals another important advantage of these anisotropic materials - enormous scaling potential, which, however, could be technically exploited by only relying on doped epitaxial layers. Recently, employing Tm-doped epitaxial layers grown on un-doped KLu(WO4)2 (KLuW) and 4 pump passes, we achieved 47% slope efficiency and CW output power of 5.9 W [2]. Here, we study the power scaling potential of this laser in the quasi-CW (QCW) mode.

High-Efficiency Thin-Disk Tm-Laser Based on 5 at. % Tm:KLu(WO4)2/KLu(WO4)2 Epitaxy

A diode-pumped thin-disk epitaxial laser with 5 at. % Tm:KLu(WO4)2/KLu(WO4)2 emits in the 1850-1920-nm spectral range with slope efficiency of 47% and maximum output power of ~6 W in continuous-wave operation.

Optical ceramics from neodymium-activated yttrium oxide

The results of investigations of mechanical, optical and laser characteristics of ceramics made from neodymiumactivated yttrium oxide are presented. The ceramics was fabricated with the use of a new technology including Laser synthesis of nanopowders and their magnetic pulsed compaction (LSN&MPC). The fracture toughness ΚIC = 0,9 - 1,4 MPa•m1/2) and microhardness (HV = 11,8 GPa) of the ceramics have been determined. It has been found that ceramic samples sintered in the temperature range from 1550 to 2050°C have (1 - 150) vol. ppm porosity and optical loss coefficient α1,07 μm = 0,03 - 2,1 cm-1. It has been shown that pore content in this range did not influence on the optical loss coefficient. Laser generation at λg ≈ 1,08 μm with a slope efficiency of 15 % at laser diode pumping has been obtained in 1.1 mm thickness sample with α1,07 μm = 0,03 cm-1.