  In this work we derive the asymptotic quasi-normal modes of a BTZ black hole
using a quantum field theoretic Lagrangian. The BTZ black hole is a very
popular system in the context of $2+1$-dimensional quantum gravity. However to
our knowledge the quasi-normal modes of the BTZ black hole have been studied
only in the classical domain. Here we show a way to quantize the quasi-normal
modes of the BTZ black hole by mapping it to the Bateman-Feschbach-Tikochinsky
oscillator and the Caldirola-Kanai oscillator. We have also discussed a couple
of other black hole potentials to which this method can be applied
