Superradiant Laser with Ultra-Narrow Linewidth Based on ⁴⁰Ca

An experiment setup for narrow linewidth superradiant laser based on the mechanism of an active optical clock is proposed with optical lattice trapped ⁴⁰Ca. We obtain the threshold pumping rate analytically and deduce the linewidth of the superradiant laser in a bad cavity regime. The proposed laser has an extremely narrow linewidth at millihertz level and a power level of order 10⁻⁹ W.