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Coherent: Briefly explain what specific research earned you the prize. Dr. Li: We invented a femtosecond laser source, the adaptive excitation source, to reduce the power requirement for two- or three-photon imaging of brain activity in the awake mouse. In our approach, an initial structural image of the targeted set of neurons is then used as a spatial key to turn an adaptive laser source on and off, during subsequent activity scans. In this way, the laser power is only “on” as the beam passes over the neurons of interest. Very importantly, we use a MOPA arrangement where the power modulation is implemented by an electro-optic modulator (EOM) located between the low-power oscillator and the amplifier. Consequently, virtually none of the amplifier gain is wasted - unlike previous attempts by other researchers where the power was blocked after the amplifier. The result is up to 30X increase in excitation efficiency for a given MOPA power rating. Coherent: Does that mean that imaging speed is the main advantage? Dr. Li: Speed is actually just one of three potential advantages. Our adaptive source has the potential to increase the speed of the two-photon imaging from 30 Hz to 1 kHz, which will enable real-time recording of fluorescent voltage indicators at the speed of neuronal activity. It also has the potential to increase the penetration depth of three-photon imaging, which will enable recording of the neuronal activity in deeper brain areas. In addition, it has the potential to increase the field-of-view for two- and three-photon imaging, which will enable high-throughout recording of larger neural circuits. Coherent: Are you planning to pursue these in your new position in China? Dr. Li: Yes, I will pursue these in my new position in the Institute for Translational Brain Research, at Fudan University. Multiphoton imaging is obviously a very important methodology to increase our understanding of the brain. I plan to develop several novel microscopes to exploit the three advantages I mentioned, as well as next-generation adaptive excitation sources for use in multiphoton microscopes. The funding from the Bernard J. Couillaud prize is being used to help me accelerate these efforts. Coherent: Have you noticed other groups becoming interested in these types of adaptive sources? Dr. Li: Yes, many groups seem to be excited by our adaptive source, in particular early adopters in neuroscience. My background is laser physics, and I’m always impressed by neuroscientists working in such a demanding field. They are typically willing to use any technology innovations to solve their problems, including ours. Coherent: What other projects are you possibly thinking about? Dr. Li: I am also interested in the translation of other types of optical imaging methods to neuroscience. The Institute for Translational Brain Research was only established in 2019, yet it has already attracted many leading neuroscientists in China as well as young principal investigators from all over the world. So I’m looking forward to collaborating with some very talented people and I hope we will solve some important neuroscience problems together. Coherent: How do you compare doing research in China vs the USA? Dr. Li: I haven’t really seen any huge difference when doing research in China vs the USA. Almost all the scientists I know simply enjoy and focus on their research. Perhaps the one slight difference I found is that people are happy to work harder in China; for example, many PhD students and postdoc volunteer for additional research after normal work time. Coherent: Thank you for this insight into your research and your future plans. As a leader in ultrafast lasers, it’s really exciting to see how your cutting-edge developments in laser sources will lead to new insights in neuroscience with potential human benefits in medicine and beyond. We are really happy to see Bernard’s legacy attached to such interesting and important work. |
