Center for Relativistic Laser Science

2019 123rd KCS

Most of biomolecules and medicines has optical activity, such as circular dichroism(CD) and optical rotation dispersion(ORD). Therefore, it is of great importance to develop techniques to investigate optical activity. Since CD is a extremely weak value, time-resolved CD spectroscopy is experimentally challenging. Here, we demonstrated that it is possible to measure electronic optical activity free-induction-decay(OA-FID) field of Ni-(tartrate)₂ with dual frequency-comb in femtosecond scale. We utilized frequency combs whose the carrier envelop frequencies are stabilized and set to 0 and, the repetition rates are stabilized and detuned in slightly different frequency(80 MHz, 80MHz+25.6Hz) at a 800 nm center wavelength. By measuring parallel FID field in time domain and transforming the measured quantities in time domain into frequency domain via fast Fourier transform, the complex susceptibility can be obtained, whose imaginary parts and real parts are related to circular dichroism(CD) and optical rotation dispersion(ORD), respectively. With Dual frequency comb, OA-FID can be measured with simple instrumentation and high data acquisition speed. We anticipate that time-resolved CD spectroscopy with DFC can bring tremendous advantages to the dynamic studies of optically active molecules.