研究目的
To present a time-resolved, phase-sensitive second harmonic generation (SHG) method for probing the excited state dynamics of interfacial species, specifically the dye malachite green at the air/water interface.
研究成果
The new time-resolved technique for studying dynamics at the interface between bulk centrosymmetric media improves phase-sensitive SHG measurements by using a spatially varying phase unit and a 30 kHz lock-in measurement. It demonstrates excellent sensitivity to phase changes and short data acquisition times, as shown by the dynamics of malachite green at the water/air interface.
研究不足
The inclusion of the wedges limits the ultimate time-resolution due to the delay experienced by the LO and fundamental pulses along the pulse front. The current sample rotation speed is not sufficient to ensure a fresh part of the surface is interrogated for each pulse pair.
1：Experimental Design and Method Selection:
The method is based on an interference measurement between the SHG from a sample and a local oscillator generated at a reference surface, using a spatially varying phase unit comprised of a pair of wedges that sandwich the reference sample.
2：Sample Selection and Data Sources:
The study uses malachite green (MG) as a cationic adsorbate at the ambient water/air interface.
3：List of Experimental Equipment and Materials:
A Yb:KGW laser system, optical parametric amplifier (OPA), CaF2 wedges, β-barium borate (BBO) crystal, rubidium titanyl phosphate (RTP) crystal, Pockels cell, Wollaston prism, and a CCD camera.
4：Experimental Procedures and Operational Workflow:
The fundamental probe beam is generated and passed through a wedge pair to produce a local oscillator. The pump beam is modulated at 30 kHz and focused onto the sample surface. The interference pattern is recorded in a single shot on a CCD camera.
5：Data Analysis Methods:
The interference pattern is analyzed using Fourier transform to extract amplitude and phase information.
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