J. Lee et al., Measurement of absorption efficiency by a leakage power analysis method from an efficient Nd : YAG rod laser pumped by diode bars, JPN J A P 1, 38(5A), 1999, pp. 2769-2774
We proposed a leakage power analysis method to measure the absorption effic
iency of a diode side-pumped Nd:YAG rod laser which was fabricated using a
3-fold symmetric gold-coated flow tube. The pump power from the 3 diode bar
modules was coupled into the reflector through AR-coated windows. A maximu
m output power of 150W with a slope efficiency of 47% was obtained from a N
d:YAG rod of 4 mm diameter at the diode pump power of 434 W. which correspo
nds to an optical efficiency of 34.6%. We investigated the thermally induce
d lens and pump light distribution of the 4-mm and 6-mm rods. The high slop
e efficiency originated from the wing-pumping scheme, uniform pump light di
stribution and the high absorption efficiency. By fixing the wavelength of
the diode at 802.4 nm, we measured the absorption efficiency, using the lea
kage power analysis method, which agreed well with the results obtained usi
ng the Findlay-Clay method. Therefore, the leakage powel analysis method wa
s demonstrated to be simpler and more reliable because it gives accurate va
lues without the need to adjust diode wavelength. An absorption efficiency
of 94% was measured for the case of a 4-mm rod.