  In this paper we propose a new optical ring resonator with a very high
Q-factor, to be used as a basic element in a wide range of physics and
engineering applications. We theoretically demonstrate that in large size
conventional ring resonators, a value of the Q-factor higher than 109 is
achievable by exploiting the band-edge resonances in a waveguiding long period
Bragg grating closed loop, excited through a bus waveguide. The dispersion
introduced by the Bragg grating is responsible for a reduction in the band edge
resonance linewidth, which is inversely proportional to the square of the
number of periods of the grating, thus allowing the overall Q-factor to be
enhanced. Numerical results show a substantial improvement in the Q-factor,
giving a number of order of magnitude higher than that of a conventional large
size ring resonator.
