  Photoluminescence (PL) of Lu$_{2}$SiO$_{5}$ crystal and ceramics with a high
concentration of oxygen vacancies (about ~0.5 at.%) is studied. Oxygen
vacancies were created using two ways. The first method is a growth of crystal
from the non-stoichiometric Lu$_{2}$Si$_{0.98}$O$_{4.96}$ melt and the second
one is a doping of Lu$_{2}$SiO$_{5}$ matrix with divalent Ca$^{2+}$ ions at the
concentration of 1 at.%. For the first time we observe a fairly bright
room-temperature ultraviolet PL of both crystal grown from the
Lu$_{2}$Si$_{0.98}$O$_{4.96}$ melt and Lu$_{2}$SiO$_{5}$ ceramics doped with
Ca$^{2+}$ ions. A band at 290 nm in the PL spectrum of the crystal and a band
at 283 nm in the PL spectrum of the calcium-doped ceramics are observed. The
spectral and kinetic properties of these bands are close to each other. This
fact indicates similar origins of these bands. The results of the work show
that the studied ultraviolet luminescence is related to oxygen vacancies in
lutetium oxyorthosilicate.
