2018, Pavlov, S. G., Deßmann, N., Redlich, B., van der Meer, A. F. G., Abrosimov, N. V., Riemann, H., Zhukavin, R. Kh., Shastin, V. N., Hübers, H.-W.

We report on an optically pumped laser where photons are simultaneously generated by population inversion and by stimulated Raman scattering in the same active medium, namely crystalline silicon doped by bismuth (SiBi). The medium utilizes three electronic levels: ground state [|1

2017, Rose, B.C., Tyryshkin, A.M., Riemann, H., Abrosimov, N.V., Becker, P., Pohl, H.-J., Thewalt, M.L.W., Itoh, K.M., Lyon, S.A.

We achieve the strong-coupling regime between an ensemble of phosphorus donor spins in a highly enriched 28Si crystal and a 3D dielectric resonator. Spins are polarized beyond Boltzmann equilibrium using spin-selective optical excitation of the no-phonon bound exciton transition resulting in N=3.6×1013 unpaired spins in the ensemble. We observe a normal mode splitting of the spin-ensemble–cavity polariton resonances of 2g√N=580  kHz (where each spin is coupled with strength g) in a cavity with a quality factor of 75 000 (γ≪κ≈60  kHz, where γ and κ are the spin dephasing and cavity loss rates, respectively). The spin ensemble has a long dephasing time (T∗2=9  μs) providing a wide window for viewing the dynamics of the coupled spin-ensemble–cavity system. The free-induction decay shows up to a dozen collapses and revivals revealing a coherent exchange of excitations between the superradiant state of the spin ensemble and the cavity at the rate g√N. The ensemble is found to evolve as a single large pseudospin according to the Tavis-Cummings model due to minimal inhomogeneous broadening and uniform spin-cavity coupling. We demonstrate independent control of the total spin and the initial Z projection of the psuedospin using optical excitation and microwave manipulation, respectively. We vary the microwave excitation power to rotate the pseudospin on the Bloch sphere and observe a long delay in the onset of the superradiant emission as the pseudospin approaches full inversion. This delay is accompanied by an abrupt π-phase shift in the peusdospin microwave emission. The scaling of this delay with the initial angle and the sudden phase shift are explained by the Tavis-Cummings model.