The last day of the conference began with a donut party, including Starbucks coffee, to provide the staples of sugar, fat, and caffeine (the real brain-food) needed to finish the last talks of breakthrough research.
On the other hand, the last poster session, Light-matter Interactions, Ultrafast and Quantum Optics, began with staples of laser-science research to include a wide range of fundamental work, instrumentation, and applications. THz optics was well represented including THz generation, spectroscopy, and detection. A number of posters showed recent breakthroughs in coherent phonon spectroscopy, single photon sources, entangled sources, quantum dot lasers and applications, and ultrafast pulse generation, compression, and characterization.
Two particularly unique posters came from two different groups in Canada, JTh2A.5, “Real-time depth monitoring of galvo-telecentric laser machining by inline coherent imaging” by Ji et al. from Queens University and Laser Depth Dynamics Corporation in Kingston, ON, and JTh2A.21, “Temporal zone plates for linear pulse compression,” by Li et al. from INRS-EMT in Montreal, QC.
Li et al. showed the temporal analog a spatial Fresnel zone plate for pulse compression. The INRS group has a history of taking spatial optic concepts and moving them to the time-domain to build clever ultrafast optical-signal processing devices. In this work, they take CW light and “focus” it to 45 ps by using the temporal zone plate as a time-lens, analogous to how one would use a spatial zone plate as spatial lens to focus a beam. They are able to convert greater than 30% of the CW signal into the pulse, showing promise for simple, compact, fiber-integrated pulse generation for various applications.
On the other hand, Ji et al. demonstrated real-time depth monitoring during laser micromachining by integrating spectral-domain OCT with a laser mill. Typically depth determination for telecentric laser micromachining is determined by calibrating laser parameters with many trial runs on the material of interest. Despite being wasteful and time-consuming, this would not work when you need to know depth information immediately and mill correctly the very first time you ablate material, say on a human skull during surgery.