Chiral Transient Grating Spectroscopy (C55-9a)

C55-09a-270378Time-resolved circular dichroism spectroscopy has increasingly been used to probe the dynamic spin states of advanced materials like metal-halide perovskites and spintronic semiconductors. Conventional spectroscopic techniques, however, average thousands of non-sequential left-handed and right-handed circularly polarized spectra together before generating a circular dichroism spectrum, leading to long acquisition times and significant baseline drift in time-resolved experiments. These drawbacks limit the accessibility of time-resolved circular dichroism spectroscopy, and hampers efforts to develop new diagnostic platforms for the advancement of next-generation energy and communication technology. In this proposal, PSI proposes the modeling, design, and validation of a transient-grating, time-resolved circular dichroism module for background-free, wavelength-agnostic investigations of material chirality. This approach uses two, cross-polarized laser pulses to induce a transient grating in sample that deflects a third probe pulse if, and only if, the sample has a circular dichroism response at that wavelength. The lack of any electro- optical devices or bandwidth limiting optics in the transient grating approach allows for a versatile spectrometer aimed at making time-resolved circular dichroism an accessible diagnostic technique for next-generation material characterization. The Phase I program will involve the development of an instrument model, the initial optical design of the transient grating spectrometer, a validation experiment, and the design of a prototype module. The commercial application of the transient-grating, time-resolved circular dichroism model stems from the technique’s continued application in measuring the complicated spin-dynamics of advanced material systems. The module will be made versatile enough that continued development beyond Phase II will result in a general platform for four-wave mixing techniques with diagnostic capabilities for these novel materials. A suitably general spectrometer has the ability to provide a significant characterization advance for materials used in next-generation energy and communication technology.