Effective Fluorescence Lifetime and Stimulated Emission Cross-Section of Nd/Cr:YAG Ceramics under CW Lamplight Pumping

Abstract

Remarkable improvements in the lifetime of the Nd upper level and in the effective stimulated emission cross-section of Nd/ Cr:YAG ceramics have been theoretically and experimentally studied. Until recently, it had been thought that the long energy transition time from Cr ions to Nd ions of Nd/Cr:YAG adversely affects laser action, degrading optical-optical conversion efficiency under CW and flash lamp pumping. However, current research showed that high-efficiency energy transition has a positive effect on laser action. The effective lifetime is increased from 0.23 to 1.1 ms and the emission cross-section is effectively increased to three times for that of the conventional Nd:YAG. A small signal gain is significantly improved, and the saturation power density is reduced to 1/10 that of the Nd:YAG for the same pumping power density. A CW laser light generated in a laser diode (LD)-pumped 1064 nm Nd:YAG laser oscillator was amplified, and the measured output power was saturated. The output laser power calculated using theoretical saturation power density was consistent with the experimental results.

Luminescence properties of highly Cr co-doped Nd:YAG powder produced by sol–gel method

“…Although Cr 3+ ions can also be doped into ceramics, higher doping concentration leads to a poor optical quality of the product due to scattering; thus, the luminescent property of highly Cr 3+ ion-doped YAG ceramics ($10 mol% Cr concentration) has not been evaluated. Since the fabrication technique of transparent ceramics has been investigated actively, the doping rate of Cr 3+ has become higher in Cr 3+ -doped YAG ceramics ($3.0 mol%) with excellent optical quality in recent years [7][8][9][10][11][12][13][14][15][16]. Therefore, it is important to know about the optical properties in the higher concentration up to around 10 mol% of Cr 3 + .…”

Nd3+- and Cr3+-Doped Yttrium Aluminum Garnet Ceramic Pulse Laser Using Cr4+-Doped Yttrium Aluminum Garnet Crystal Passive Q-Switch

“…The optical parameters of the Nd:YAG and Nd 3þ /Cr 3þ :YAG ceramic lasers are shown in Table I. 9,20,21) The effective stimulated emission cross section of the ceramic laser is very close to that of the Nd:YVO 4 laser. The profile of the Nd 3þ /Cr 3þ :YAG ceramic rod is square and the size of the laser rod is 4 Â 4 Â 48 mm 3 .…”

“…5,6) We observed laser oscillations 7) and achieved a high optical-optical conversion efficiency of over 40%. 8) Nd 3þ /Cr 3þ :YAG ceramics have many advantages over Nd:YAG crystals, including in improved pumping efficiency by solar light, elongation of Nd upper level lifetime, an effective stimulated emission cross section owing to cross pumping from Cr 3þ to Nd 3þ ions, 5,9) and a high thermal conductivity compared with Nd/Cr:GSGG crystals. Ceramics have a remarkable advantage in scalability with doping Cr 3þ ions at a high concentration compared with single crystals, with reducing Cr 4þ ions.…”

Energy transfer in YAG ceramics codoped with Nd³⁺ and Cr³⁺

“…Absorption spectra of Cr 3 + ions in ionic crystals, for example , Y 3AIsOl2 (YAG) cover the visible range (400-700 nm). YAG ceramics codoped with Nd 3 + and Cr 3 + ions are renewed as a laser medium with excitation of solar energy because of highly efficient energy transfer from Cr 3 + to Nd 3 + ions [3,4].YAG ceramics codoped with lat.% Nd 3 + and O.lat.% Cr3+ were sintered by Konoshima Chemical Company. Fluorescence spectra and decay curves were measured in the temperature range of 100-500 K using excitation of tunable laser light from an OPO (Lotis-TI , LT2215), a near infrared InGaAs detector (Thorlabs, PDA400), and a digital oscilloscope (Yokogawa, DLl740).…”

“…Absorption spectra of Cr 3 + ions in ionic crystals, for example , Y 3AIsOl2 (YAG) cover the visible range (400-700 nm). YAG ceramics codoped with Nd 3 + and Cr 3 + ions are renewed as a laser medium with excitation of solar energy because of highly efficient energy transfer from Cr 3 + to Nd 3 + ions [3,4].…”