研究目的
Investigating the emergence of limit cycles in coupled polariton cavities and their manifestation as frequency-comb emission.
研究成果
The study demonstrates the formation of limit cycle oscillations in dissipatively coupled nonlinear polariton condensates, characterized by the generation of equidistant new frequency components, coherence revivals in g(1)(τ), asymmetric distribution in both real and Fourier space, and a nontrivial relative phase that is neither zero nor π. These findings establish coupled polariton cavities as a platform for exploring rich nonlinear dynamic phenomena and potential applications in nonresonantly pumped, low-power sources of microfrequency combs or terahertz waves.
研究不足
The study is limited by the need for large on-site interaction α ? μ to produce the limit cycles, which can be realized with tight confinement of the EPs. Additionally, the dissipative coupling rate γ is estimated to be about one-tenth of the cavity decay rate, which may limit the observability of the limit cycle state under certain conditions.
1：Experimental Design and Method Selection:
The study involves the use of a pair of tightly confined, single-mode exciton-polariton (EP) cavities with controlled couplings to demonstrate limit cycle oscillations. The dynamics are modeled using nonlinear Gross-Pitaevskii equations that include pumping, loss, and polariton nonlinearities, as well as both coherent and dissipative coupling between the two sites.
2：Sample Selection and Data Sources:
A GaAs-based microcavity device is used, with the top mirror consisting of a Al
3：15Ga85As subwavelength grating (SWG) suspended over a short distributed Bragg reflector (DBR). The sample is kept at 5 K and excited by a continuous-wave Ti:
sapphire laser.
4：List of Experimental Equipment and Materials:
The setup includes a closed-cycle cryostat, a continuous-wave Ti:sapphire laser, an electro-optic modulator, and a Michelson interferometer for coherence measurements.
5：Experimental Procedures and Operational Workflow:
The pump spot is focused on the center of the device with a diameter of 2 μm. The power dependence of the spectral and spatial distributions of the emission is measured to observe signatures of the limit-cycle state.
6：Data Analysis Methods:
The temporal first-order coherence g(1)(τ) is measured using a Michelson interferometer to verify the uniformity of the mode spacing and phase coherence between the multiple frequency lines.
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