Multiple weak-line laser operation from Nd:YAG 4F3/2-4I13/2 translation in ceramic and crystal

Abstract

Laser diode end-pumped Nd:YAG based multiple weak-lines laser from 4F3/2-4I13/2 translation is reported. Fluorescence spectra for both Nd:YAG crystal and ceramic are present. Simple two-mirror cavity with reasonable optical coating is used for multiple weak-line laser operation around 1.3 and 1.4 μm. The variations of laser output and spectra with the pump power are compared experimentally between 1.0 at.% Nd3+ doped Nd:YAG ceramic with 3 mm×3 mm×7.5 mm in size and 0.8 at.% Nd3+-doped Nd:YAG crystal with 3 mm×3 mm×8 mm in size. First, 1338 and 1356 nm dual-wavelength laser outputs are achieved using output coupler with transmittance values of 9.6%, 6.2%, 2.4% and 1.8% at 1338, 1356, 1414 and 1444 nm, respectively. Under low pump power around the threshold, the 1356 nm single wavelength laser is obtained. With increasing the pump power, the laser with a wavelength of 1338 nm appears first in the ceramic. At an incident pump power of 11.8 W, a 1338 and 1356 nm dual-wavelength laser with an output power of 3.7 W and an intensity ratio of 1 : 5 for crystal, and a 1338 and 1356 nm dual-wavelength laser with an output power of 3.5 W and an intensity ratio of 1:3 for ceramic are obtained. Replacing the output couplers with transmittance values of 15.4%, 6.5%, 1.1% and 0.8% at wavelengths of 1338, 1356, 1414 and 1444 nm, respectively, 1356 and 1414 nm dual-wavelength laser outputs are achieved. Under the low pump power, even triple-wavelength (1356, 1414 and 1444 nm) laser is obtained. With increasing the pump power, the intensities of 1414 and 1444 nm wavelengths turned down and the 1444 nm wavelength disappears first in ceramic. At an incident pump power of 11.8 W, a 1356 and 1414 nm dual-wavelength output power of 3.56 W with intensity ratio of 44 : 1 for crystal and a 1356 and 1414 nm dual-wavelength laser output power of 3.25 W with intensity ratio of 12 : 1 for ceramic are obtained. The results show that slight difference between fluorescence spectra results from the difference in laser spectrum between transparent ceramic and single crystal materials for multi-wavelength output. Thresholds of two different output couplers are both about 2 W. When the incident pump power increases to 13.5 W, a 1338 and 1356 nm dual-wavelength laser output power of 4.05 W and a 1356 and 1414 nm dual-wavelength laser output power of 3.65 W are achieved in Nd:YAG transparent ceramic. The corresponding slope efficiency values are 33.9% and 31.9%, respectively.