Bing Gu

Our paper on the optical properties of laser-driven matter is published in Phys. Rev. A. In this work, we develop a theory of optical absorption that is valid for non-equilibrium systems, in particular, laser-driven systems. We applied this theory to investigate the emergent optical absorption properties of a nanoscale semiconductor driven by a intense non-resonant light. It turns out that the optical absorption properties of a laser-driven matter is qualitatively different from the pristine material. Depending on the strength of the dressing light, it can generates replicas of absorption bands that are separated by integer number of photon energies, and generates absorption/emission signals at THz regime.

Theoretical chemists think light as semiclassical in the sense that the quantum nature of light is not affecting chemistry. Technically speaking, the light field comes into play in the basic equation to describe chemistry, time-dependent Schodinger equation, as an external time-dependent parameters. However, light is quantum mechanical in nature. And with the advent of nonclassical light realized in labrarotory, it is essential to go beyond the semiclassical view and take a full quantum mechanical treatment of light. 

If you are interested in a deep understanding of light, the book “Quantum Optics” by Scully and Zubairy is an excellent book that gives a comprehensive introduction to the quantum mechanical properties of light. The prerequisite, in my opinion, is familiarity with basic quantum mechanics. 

I officially start my postdoc position at the University of California, Irvine working with Prof. Shaul Mukamel. I will work on manipulating and controlling chemistry by optical cavities.

Our paper on the relationship between electronic interaction and electronic decoherence is published in J. Chem. Phys. In it, we showed that the electronic interactions do not affect electronic decoherence in the pure-dephasing limit, that is when the electronic transitions between the diabatic states are not significant. 

The book “Nonlinear optics” by Robert W. Boyd is excellent. One can find essentially everything about nonlinear optics in this book. While this book is not written particularly for chemists (as the nonlinear media is not always consist of molecules), majority of the concepts and treatments are beneficial to chemists. The treatment is a combination of quantum mechanics for matter and Maxwell equations for light. The chemists intended to focus on how light changes matter without considering the change of light (the light acts as a parameter in the equations of motion for matter).  But matter also changes light, and we have to combine both views to have a complete picture of laser-matter interaction.

Since I am going to join Prof. Shaul Mukamel group soon, I recently read his book  “Principles of nonlinear optical spectroscopy” again. This is an excellent book for nonlinear spectroscopy in molecules. Although I do think it is a little bit technical in the sense that it goes into the third-order dipole response functions w.r.t. the external electric field. But after getting some familiarity with the mathematical language (i.e. Liouville space pathways), it becomes a wonderful reading experience.

The book “Quantum Mechanics and Path Integrals” by Feynman and Hibbs gives an excellent introduction to the path-integral view of quantum mechanics. This formulation of quantum mechanics, albeit conceptually equivalent to many other formulations, provides a unique perspective to solve problems. One example is that it builds a natural connection to statistical mechanics. And also it has been the foundation of a variety of numerical methods to simulated quantum dynamics for large-scale systems (hundreds of atoms).

It will be an enjoyable reading experience if one has a basic understanding of the quantum mechanics.