Lotka-Volterra population dynamics in coherent and tunable oscillators of trapped polariton condensates

We demonstrate a regime in which matter-wave condensates of exciton-polaritons trapped in an elliptically shaped two-dimensional potential appear as a coherent mixture of ground and first-excited state of the quantum harmonic oscillator. This system resembles an optically controllable two-level system and produces near terahertz harmonic oscillations of the condensate’s center of mass along the major axis of the elliptical trapping potential. The population ratio between the two trap levels is tunable through the excitation laser power and is shown to follow Lotka-Volterra dynamics. Furthermore, we demonstrate coherence formation between two spatially displaced trapped condensate oscillators - the polaritonic analogue of Huygen’s clock synchronization for coupled condensate oscillators

Direct measurement of carbon nanotube temperature between fiber ferrules as a universal tool for saturable absorber stability investigation

Single-walled carbon nanotubes (SWCNTs) are widely explored for the ultrashort pulse generation in the fiber lasers enabled by pronounced saturable absorption (SA) effect. Despite many remarkable results demonstrated in the area, degradation of the samples inside the laser cavity limits the widespread use of SWCNT-SA. In the present work, we investigate the degradation mechanism by measuring the temperature of the carbon nanotubes in an operating laser cavity in accordance with the Raman G-band position. We identify the process behind the sample degradation by comparing the burning temperature of the sample with results of thermogravimetric analysis. We apply this approach for the SWCNTs in polyvinyl alcohol polymer matrix and polymer-free SWCNT thin film and demonstrate that these samples undergo different degradation mechanism. Proposed technique provides a useful instrument for optimization of SWCNT-SA for desired ultrafast laser generation