  Traditional lasers function using resonant cavities, in which the round-trip
optical path is exactly equal to an integer multiple of the intracavity
wavelengths to constructively enhance the spontaneous emission rate. By taking
advantage of the enhancement from the resonant cavity, the narrowest
sub-10-mHz-linewidth laser and a $10^{-16}$-fractional-frequency-stability
superradiant active optical clock (AOC) have been achieved. However, a laser
with atomic spontaneous radiation being destructively inhibited in an
anti-resonant cavity, where the atomic resonance is exactly between two
adjacent cavity resonances, has not been reported. Herein, we experimentally
demonstrate inhibited stimulated emission and termed it an inhibited laser.
Compared with traditional superradiant AOCs, which exhibit superiority in terms
of the high suppression of cavity noise, the suppression of the cavity-pulling
effect of an inhibited laser can be further improved by a factor of
$(2F/pi)^2$, i.e., 2.07 in this work, which was improved from 26 to 53 times.
This study will guide further development of AOCs with better stability, and
thus, it is significant for quantum metrology and may lead to new research in
the laser physics and cavity quantum electrodynamics fields.
