Photonic features laser oscillation

Very recently, Sasaki et al. fabricated a microring laser by making the most of the various semiconductor processing methods, and achieved low-threshold laser oscillation [51]. This demonstrates the robustness of thiophene-based oligomers and that these materials are compatible with semiconductor processing. 

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We can explain these features by considering the equations of motion (96) for the density matrix elements. When A = 0, and the laser is tuned to the middle of the upper levels splitting the states 1) and 3) are equally driven by the laser and the coherences p12 and p32 oscillate in phase with frequency A/. The coherences are directly coupled by the cross-damping term I ) 2. However, for a strong driving field (fl 3> F) the Rabi oscillations dominate over the spontaneous exchange of photons, resulting in independent oscillations of the atomic dipole moments. 

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