The second threshold of a superradiant laser

А. Н. Ораевский

Nikita Yu. Gordeev, Leonid Ya. Karachinsky, V. I. Kopchatov +2 more

Mechanism of laser threshold is considered in terms of superradiance. Presence of short Coherent pulses has been demonstrated below at and above laser threshold in wide temperatwe range. Existence of positive feedback leads to SR pulse becomes longer. Luminescence lineshape above threshold has a complex structure but is well described using the theory of collective recombination. Spectral investigations at low and room temperatwe. as well as time coherence measurements at RT allow estimating the characteiistic time of superradiance pulse in these two modes. The maximum duration of the pulse has been found as low as 300 fs at RT and 70 fs at 77 K.

Fritz Haake, M. I. Kolohov, Claude Fabre +2 more

Yanfei Wang, Jingbiao Chen

An experiment setup for narrow linewidth superradiant laser based on the mechanism of an active optical clock is proposed with optical lattice trapped 40 Ca. 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.

James K. Thompson

Hideaki Hara, Riku Omoto, N. Sasao +6 more

To achieve more controllable development of coherence in solids, we investigated the effect of a trigger laser tuned to the superradiance transition wavelength on periodic superradiance observed in an Er:YSO crystal. For period control, applying the trigger laser reduced both the superradiance period and its variance, demonstrating enhanced controllability of coherence development dynamics. As the trigger laser power increased, both the period and the number of emitted superradiance photons decreased while maintaining a proportional relationship. This behavior is explained by a reduced superradiance threshold under a constant excitation rate and is reproduced by numerical simulations based on the Maxwell-Bloch equations. For timing control, we found that superradiance could be triggered even when the excitation laser alone was insufficient. This enabled us to control the emission timing of superradiance using short trigger pulses and provided a device capable of generating superradiance at desired timing.