It is reported about the first observation and
studying of the photon echo in
LuLiF~4~:Er^3+^. The energy transition is
^4^I~15/2~โ^4^F~9/2~ (ฮป=6536 ร
). The
density of ErF~3~ is 0.025 wt%. The operation temperature is
1.9 K. Measurements were spent at low (up to 1200 Oe) and even
zero external magnetic fields. It was studied a behavior of the
photon echo intensity versus the magnetic field magnitude and
direction about the crystal axis C and versus the laser
pulse separation t
~12~. It was observed an exponential growth
and then, after some plateau, an exponential decreasing of the
photon echo intensity as a function of magnetic field with
increasing of the magnetic field from zero value. The parameters
describing the exponential growth and decreasing are not depended
on direction of magnetic field. Value of a magnetic field at which
the echo intensity accepts the maximum, and quantity of this
maximum decrease with increased the pulse separation t
~12~ and
the angle ฮธ between the magnetic field and crystal axis.
The echo intensity exponentially decreases with increased
ฮธ. The parameter describing the exponential decreasing is
not depended on the magnitude of the field. The echo intensity as
a function of pulse separation shows exponential decay. The phase
relaxation time is depended on the magnitude and direction of the
magnetic field. T
~2~ is equal to 202ยฑ16 ns at zero magnetic
field. Phenomenological formula is suggested, which qualitatively
presents the mentioned dependencies. Polarization properties of
the backward photon echo in this crystal are studied also.