7.3 W of single-frequency output power at 2.09 μm from an Ho:YAG monolithic nonplanar ring laser

Single-frequency output power of 7.3 W at 2.09 mu m from a monolithic Ho:YAG nonplanar ring oscillator (NPRO) is demonstrated. Resonantly pumped by a Tm-doped fiber laser at 1.91 mu m, the Ho:YAG NPRO produces 71% of slope efficiency with respect to absorbed pump power and nearly diffraction-limited output with a beam quality parameter of M-2 approximate to 1.1. (c) 2008 Optical Society of America

Diode-pumped room-temperature continuous wave Tm3+ doped Lu2SiO5 laser

We report on room temperature laser actions of a novel thulium-doped crystal Tm center dot Lu2SiO5 (LSO) under diode pumping. An optical optical conversion efficiency of 12% and a slope efficiency of 21% were obtained with the maximum continuous wave (CW) output power of 0.67 W. The emission wavelengths of Tm LSO laser were centered at 2058.4 nm with bandwidth of similar to 13.6 nm.

Judd-Ofelt analysis of spectra and experimental evaluation of laser performance of Tm3+ doped Lu2SiO5 crystal

This paper reports that the TM3+:Lu2SiO5 (Tm:LSO) crystal is grown by Czochralski technique. The room-temperature absorption spectra of Tm:LSO crystal are measured on a b-cut sample with 4 at.% thulium. According to the obtained Judd-Ofelt intensity parameters Omega(2)=9.3155 x 10(-20) cm(2), Omega(4)=8.4103 x 10(-20) cm(2), Omega(6)=1.5908 x 10(-20) cm(2), the fluorescence lifetime is calculated to be 2.03 ms for F-3(4) -> H-3(6) transition, and the integrated emission cross section is 5.81 x 10(-18) cm(2). Room-temperature laser action near 2 mu m under diode pumping is experimentally evaluated in Tm:LSO. An optical-optical conversion efficiency of 9.1% and a slope efficiency of 16.2% are obtained with continuous-wave maximum output power of 0.67 W. The emission wavelengths of Tm:LSO laser are centred around 2.06 mu m with spectral bandwidth of similar to 13.6 nm.

Holmium laser in-band pumped by a thulium laser in the same host of YAlO3

We report on the room-temperature continuous-wave (CW) operation of a Ho:YAlO3 laser that is resonantly end pumped at 1.94 mu m by a diode-pumped thulium-doped laser in the same host. Through the use of a 1 at % Ho3+-doped 20-mm-long YAlO3 crystal (b cut), the Ho:YAlO3 laser generated 1 W of linearly polarized (E//c) output at 2118 nm and 0.55 W of E//a output at 2128.5 nm for an incident pump power of 5 W, with an output coupler transmission of 14 and 3%, respectively. An optical-to-optical conversion efficiency of 20% and a slope efficiency of 33% were achieved at 2118 nm corresponding to an incident pump power.

Continuous-wave and Q-switched operation of a resonantly pumped Ho:YAlO3 laser

We demonstrated continuous-wave ( CW) and Q-switched operation of a room-temperature Ho: YAlO3 laser that is resonantly end-pumped by a diode-pumped Tm: YLF laser at 1.91 mu m. The CW Ho: YAlO3 laser generated 5.5 W of linearly polarized (E parallel to c) output at 2118 nm with beam quality factor of M-2 approximate to 1.1 for an incident pump power of 13.8 W, corresponding to optical-to-optical conversion efficiency of 40%. Up to 1-mJ energy per pulse at pulse repetition frequency (PRF) of 5 kHz, and the maximum average power of 5.3-W with FWHM pulse duration of 30.5 ns at 20 kHz were achieved in Q-switched mode. (C) 2008 Optical Society of America.

Diode-pumped Q-switched Tm:YAP laser with a pump recycling scheme

We reported on a diode end-pumped AO Q-switched Tm:YAP laser at 1937 nm. The average output power was 3.9 W, with a slope efficiency of 29.4% and optical-optical conversion efficiency of 21.6% at a 5-kHz repetition rate. The temperature dependency of the output power and the pulse width at different repetition rates were investigated in details.

Judd-Oflet analysis of spectrum and laser performance of Ho:YAP crystal end-pumped by 1.91-mu m Tm:YLF laser

The Ho:YAP crystal is grown by the Czochralski technique. The room-temperature polarized absorption spectra of Ho:YAP crystal was measured on a c-cut sample with 1 at% holmium. According to the obtained Judd-Ofelt intensity parameters Omega(2) = 1.42 x 10(-20) cm(2), Omega(4) = 2.92 x 10(-20) cm(2), and Omega(6) = 1.71 x 10(-20) cm(2), this paper calculated the fluorescence lifetime to be 6 ms for I-5(7) -> I-5(8) transition, and the integrated emission cross section to be 2.24 x 10(-18) cm(2). It investigates the room-temperature Ho:YAP laser end-pumped by a 1.91-mu m Tm:YLF laser. The maximum output power was 4.1 W when the incident 1.91-mu m pump power was 14.4W. The slope efficiency is 40.8%, corresponding to an optical-to-optical conversion efficiency of 28.4%. The Ho:YAP output wavelength was centred at 2118 nm with full width at half maximum of about 0.8 nm.

Laser conditioning of ZrO2 : Y2O3/SiO2 mirror coatings prepared by E-beam evaporation

Laser conditioning effects of the dielectric mirror coatings with different designs were investigated. Simple quarter-wave ZrO2:Y2O3/SiO2 mirrors and half-wave SiO2 over-coated ZrO2:Y2O3/SiO2 mirror coatings were fabricated by E-beam evaporation (EBE). The absorbance of the samples before and after laser conditioning was measured by surface thermal lensing (STL) technology and the defects density was detected under Nomarski microscope. The enhancement of the laser damage resistance was found after laser conditioning. The dependence of the laser conditioning on the coating design was also observed and the over-coated sample obtained greatest enhancement, whereas the absorbance of the samples did not change obviously. During the sub-threshold fluence raster scanning, the minor damage about defects size was found and the assumption of pre-damage mechanism, based on the functional damage concept, was put forward. The improvement of the laser induced damage threshold (LIDT) was attributed to the benign damage of the defects and the dependence on the coating design owed to the damage growth behavior of different coating designs. (C) 2004 Elsevier B.V. All rights reserved.

Optical, structural and laser-induced damage threshold properties of HfO2 thin films prepared by electron beam evaporation

We prepare HfO2 thin films by electron beam evaporation technology. The samples are annealed in air after deposition. With increasing annealing temperature, it is found that the absorption of the samples decreases firstly and then increases. Also, the laser-induced damage threshold (LIDT) increases firstly and then decreases. When annealing temperature is 473K, the sample has the highest LIDT of 2.17J/cm(2), and the lowest absorption of 18 ppm. By investigating the optical and structural characteristics and their relations to LIDT, it is shown that the principal factor dominating the LIDT is absorption.

Influence of laser preconditioning on the capacity of optical films to resist laser-induced damage

As a technique to improve the ability of optical films to resist laser-induced damage (ARLID), laser preconditioning has been investigated broadly. In this paper, the laser preconditioning effect has been analyzed based on the defect-initialized damage mechanism that the author had put forward previously. Theoretical results show that an energy density scope (PEDS) exists in which the preconditioning laser can effectively improve the ARLID of optical films. In addition, when the energy density of the testing laser pulse is altered, the boundary of PEDS will change accordingly. Experimental results have verified these theoretical assumptions. PEDS will also become wider if the critical energy density of the preconditioning laser that can induce films' micro-damage increases, or the critical energy density of the preconditioning laser that can cause laser annealing decreases. In these cases, it is relatively easy to improve the ARLID of optical films. Results of the current work show great significance in enhancing the ARLID of optical films through the laser preconditioning technique. (C) 2008 Elsevier B.V. All rights reserved.