  The superradiant laser, based on the clock transition between the electric
ground state $^1$S$_0$ and the metastable state $^3$P$_0$ of fermionic
alkaline-earth(-like) atoms, has been proposed to be a new promising light
source with linewidth being the order of millihertz. However, due to the small
$^1$S$_0$-to-$^3$P$_0$ transition strength, the steady-state power in that
system is relatively low ($\sim 10^{-12}$W). In this work, we propose an
alternative superradiant laser scheme based on a Raman-transition-induced
coupling between the $^3$P$_0$ and $^3$P$_1$ states in bosonic
alkaline-earth(-like) atoms, and achieve a laser with linewidth $\lesssim
2\pi\times1$Hz and power $\gtrsim 10^{-10}$W ($\sim 10^{3}$ photons in steady
state) at a small pumping cost. The Raman beams play two significant roles in
our scheme. First, the coherence between the dark and bright states induced by
the Raman beams produce a new local minimum in the pumping-linewidth curve with
pumping rate lower than $2\pi \times 10$kHz, which is beneficial for continuous
output. Second, the Raman beams mix the long-lived $^3$P$_0$ state into the
lasing state and thus reduce the linewidth. Our work greatly improves the
output performance of the superradiant laser system with coherence induced by
Raman transitions and may offer a firm foundation for its practical use in
future.

Quantum Physics;Atomic Physics