Applied Physics

IMG
Jonathan Blutinger, Yorán Meijers, Yichen (Peter) Chen, Changxi Zheng, Eitan Grinspun, and Hod Lipson
Characterization of CO2 Laser Browning of Dough.
Journal of Innovative Food Science and Emerging Technologies, 2018

Paper Abstract
We study the application of laser-heating technology to browning dough, due to its potential for high-resolution spatial and surface color control. An important component of this process is the identification of how laser parameters affect browning and baking and whether desirable results can be achieved. In this study, we analyze the performance of a carbon dioxide (CO2) mid-infrared laser (operating at 10.6 micrometer wavelength) during the browning of dough. Dough samples--consisting of flour and water--were exposed to the infrared laser at different laser power, beam diameter, and sample exposure time. At a laser energy flux of 0.32 MW m^{-2} (beam diameter of 5.7 mm) and sample exposure time of 180 s we observe a maximum thermal penetration of 0.77 mm and satisfactory dough browning. These results suggest that a CO2 laser is ideal for browning thin goods as well as for food layered manufacture.
IMG
Adam C. Overvig, Sajan Shrestha, Chang Xiao, Changxi Zheng, and Nanfang Yu
Two-Color and 3D Phase-Amplitude Modulation Holograms.
Conference on Lasers and Electro-Optics (CLEO), May 2018

Paper Abstract
We report a high-efficiency dielectric metasurface with continuous and arbitrary control of both amplitude and phase of one or two colors simultaneously. We numerically and experimentally demonstrate 2D and 3D holograms using such metasurfaces.
IMG
Jonathan Blutinger, Yorán Meijers, Yichen (Peter) Chen, Changxi Zheng, Eitan Grinspun, and Hod Lipson
Characterization of Dough Baked via Blue Laser.
Journal of Food Engineering, 2018

Paper Abstract
Depth of heat penetration and temperature must be precisely controlled to optimize nutritional value, appearance, and taste of food products. These objectives can be achieved with the use of a high-resolution blue diode laser---which operates at 445nm---by adjusting the water content of the dough and the exposure pattern of the laser. Using our laser, we successfully cooked a 1mm thick dough sample with a 5mm diameter ring-shaped cooking pattern, 120 repetitions, 4000mm/min speed, and 2W laser power. Heat penetration in dough products with a blue laser is significantly higher compared to with an infrared laser. The use of a blue laser coupled with an infrared laser yields most optimal cooking conditions for food layered manufacture.
IMG
Adam C. Overvig, Sajan Shrestha, Changxi Zheng, and Nanfang Yu
High-Efficiency Amplitude-Phase Modulation Holograms Based on Dielectric Metasurfaces.
Conference on Lasers and Electro-Optics (CLEO), May 2017

Paper Abstract
We report a high-efficiency dielectric metasurface with continuous and arbitrary control of both amplitude and phase. We experimentally demonstrated the advantages of complete wavefront control by comparing amplitude-phase modulation metasurface holograms to phase-only metasurface holograms.