研究目的
To demonstrate and investigate nonlinear polaritons formed via the strong coupling of excitons in monolayer MoSe2 and optical BICs in a 1D photonic crystal slab, with the aim of enhancing and controlling polariton–polariton interactions and the resulting nonlinear optical effects.
研究成果
The formation of BIC-like polaritons in a hybrid system of a monolayer semiconductor interfaced with a PCS, with suppressed radiation into the far field and line narrowing due to effective disorder averaging, extends the polariton–polariton interaction time, which enhances the nonlinear optical response. The observed nonlinearities are fast on a 100 fs scale, providing future opportunities for developing polariton-based ultrafast modulators and switches.
研究不足
The measured Q-factor is limited predominantly by nonradiative losses, including intrinsic absorption in Ta2O5 and surface-roughness-induced symmetry breaking and scattering. Additional resonance broadening comes from leaky losses in the Si due to near-field penetration through the SiO2 layer and finite sample size effects.
1：Experimental Design and Method Selection:
The study involves the fabrication of a hybrid system consisting of a monolayer MoSe2, multilayer hexagonal boron nitride (hBN), and a photonic crystal slab (PCS) to form nonlinear exciton-polaritons. The methodology includes angle-resolved reflectance spectroscopy and photoluminescence (PL) measurements to study the polaritons.
2：Sample Selection and Data Sources:
Large-area high-quality flakes of multilayer hBN and monolayer MoSe2 were mechanically exfoliated from commercial bulk crystals and stacked vertically onto the photonic crystal sample surface.
3：List of Experimental Equipment and Materials:
The equipment includes a back-focal-plane setup with a slit spectrometer coupled to a liquid-nitrogen-cooled imaging CCD camera, a wavelength-tunable Ti:sapphire oscillator for pump-dependent reflectivity measurements, and a HeNe laser for angle-resolved PL measurements.
4：Experimental Procedures and Operational Workflow:
The sample was mounted in an ultra-low-vibration closed-cycle helium cryostat for temperature control. Spatial filtering in the detection channel was used to selectively measure signals from the sample area.
5：Data Analysis Methods:
The data analysis involved fitting the wavevector-dependent behavior of the lower polariton branch (LPB), upper polariton branch (UPB), uncoupled neutral exciton, and trion with Lorentzian functions to extract spectral positions and linewidths.
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