  This thesis focuses on two different, but complementary, aspects of the
modification of gallium lanthanum sulphide (GLS) glasses. Firstly the addition
of transition metal ions as dopants is examined and their potential for use as
active optical materials is explored. It is also argued that the spectroscopic
analysis of transition metal ions is a useful tool for evaluating the local
environment of their host. Secondly femtosecond (fs) laser modification of GLS
is investigated as a method for waveguide formation.
