  We report on the charge carrier dynamics of superconducting titanium nitride
(TiN) in the frequency range 90 - 510 GHz (3 - 17 cm-1). The experiments were
perfomed on a 18 nm thick TiN film with a critical temperature of 3.4 K.
Measurements were carried out from room temperature down to 2 K, and in
magnetic fields up to 7 T. We extract the real and imaginary parts of the
complex conductivity as a function of frequency and temperature, directly
providing the superconducting energy gap. Further analysis yields the
superconducting London penetration depth. The findings as well as the normal
state properties strongly suggest conventional BCS superconductivity,
underlined by the BCS ratio 3.44. Detailed analysis of the charge carrier
dynamics of the silicon substrate is also discussed.
