Volume 6, Number 10
APPLIED PHYSICS LETTERS
May 15, 1965
(ref. 2) we observe transfer from the Er+3 absorp-
tion bands near 490 eF7/2), 660 (4F9/2 ), 810 (419/2)'
and 950 mf..t (411112); the term assignments follow
those of Er+3 in Y203 (ref 4). The fluorescent in-
tensity of 1/2% Tm+3 in Er20 3 is more than 20
EXCITATION WAVELENGTH m.u
Fig. 2. A. Instrumental response. B. Excitation spectrum of
the 1.93-1L fluorescence of 1I2-atom percent Tm+3 in Er20 3•
C. Excitation spectrum of the 1.93-1L fluorescence of 1/2-atom
percent Tm+3 in Y203'
times as intense as the emission from 1/2% Tm+3 in
Y20 3 at 77°K under tungsten excitation.
The laser experiments were conducted with a
sample approximately 1 cm in length with flat and
parallel silvered ends using a fast gold-doped
germanium detector. The threshold was less than
3 joules into a I-in. straight xenon flash lamp in
close proximity to the liquid nitrogen dewar con-
taining the sample. No laser operation could be
obtained from the nearby fluorescent lines at an
energy input of 20 joules.
The lifetime of the fluorescence is 2.9 msec at
77°K with a build-up time of about 200 f..tsec. Near-
threshold laser emission is observed 50 f..tsec after
the 250-f..tsec lamp pulse is over, an effect which is
a consequence of this build-up time.
CW operation was observed using 500-W quartz-
iodine tungsten lamps as the pumping source. In
the configuration used, the liquid nitrogen dewar
containing the sample was surrounded by an array
of 12 lamps. Threshold was reached with three
The crystals were grown by A. C. Pastor and K.
Arita under the direction of R. C. Pastor. We thank
D. Roberts for the use of the CW laser housing,
C. R. Duncan for technical assistance, and]. Mikiska
for the coatings.
'Supported by U.S. Air Force Electronic Technology Division,
A.F. Avionics Laboratory Research and Technology Division,
Wright-Patterson Air Force Base, Ohio, under Contract No.