Remote, localized photoacoustic communication is achieved using a modulated 1.9 μm Thallium laser. The message, optically encoded on the laser beam, is sent to the receiver's ear using the photoacoustic effect. No external receiver is used, instead the absorption of atmospheric water vapor near the receiver's ear is utilized to convert the message into an audible signal. Tuning operational parameters including laser wavelength and laser spot size are done to maximize sound pressure without exceeding eye-safe power densities. This work provides new methods to communicate to a remote observer without requiring the observer to possess communication equipment. Possible applications include warning applications and localized communication to a specific person in a noisy room.
The quantum and collective effects in molecular ensembles, such as photosynthetic complexes and proteins, are of great importance for understanding many peculiar phenomena. The recent experimental advance in multidimensional spectroscopy offers the powerful tools to resolve the excited-state relaxation and structural dynamics in various materials, which led to the heightened interest in quantum effects associated with these systems. The main theme in this talk will cover three interesting aspects of our recent work: Multidimensional spectroscopy through post-selection of the radiated photons , two-dimensional coherent spectroscopy for molecular polaritons  and out-of-equilibrium condensate of phonons . The first two are devoted to how the new quantum phenomena in complex systems can be studied and resolved using the advances in both quantum optics and nonlinear spectroscopy. The last one will focus on the recent development of quantum statistical theory for the collective phenomena in complex systems, such as the out-of-equilibrium condensate of phonons observed in some proteins . The theory developed here gives the full information regarding quantum fluctuations and spectroscopic features of the condensate, which are not accessible in precedent studies.