研究目的
Investigating the saturable absorption in solution-phase and cavity-coupled tungsten hexacarbonyl (W(CO)6) and its implications for infrared photonic devices.
研究成果
The study demonstrates saturable absorption in W(CO)6 in solution and shows that the Rabi splitting of cavity-coupled W(CO)6 can be saturated under high incident fluences. The reduced absorption of the vibration-polaritons leads to a sample length- and concentration-dependent saturation fluence. The large transmission modulation achieved may find applications in narrow-band photonic devices operating in the mid-infrared.
研究不足
The study is limited by the sensitivity of measurements to small changes in the cavity position and solution concentration over the course of the measurement, with estimated uncertainties as high as 30% for the experimental saturation fluence values. The calculations employed do not consider rapid energy transfer from polariton states to the reservoir of dark modes.
1：Experimental Design and Method Selection:
The study utilizes excitation pulses from a transient infrared spectrometer to investigate saturable absorption in W(CO)6, both in free space and under strong coupling to a Fabry?Pérot cavity. The setup generates ～120 fs pulses with 155 cm?1 full-width at half-maximum (fwhm).
2：Sample Selection and Data Sources:
Solutions of W(CO)6 in hexane with concentrations varying from ～1 to ～3 mM are used, contained in optical cavities comprising 92% reflective dielectric mirrors separated by PTFE spacers creating cavity lengths of 12, 25, and 56 μm.
3：List of Experimental Equipment and Materials:
The setup includes an optical parametric amplifier, difference frequency generation, infrared neutral density filters, spectrograph, and an MCT array detector.
4：Experimental Procedures and Operational Workflow:
The beam is focused to a diameter of 100 μm at normal incidence, and the pulse energy is varied from 5 μJ to 5 nJ per pulse. After the sample, the pulse is directed to a spectrograph and an MCT array detector.
5：Data Analysis Methods:
The absorption strength is taken as the amplitude of the Lorentzian line shape fit to the absorption feature, and the fluence dependence of saturable absorption is described by a standard relation.
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