Oct 6 2015
Nanfang Yu, assistant professor of applied physics at Columbia Engineering , has won the prestigious DARPA (Defense Advanced Research Projects Agency) Young Faculty Award (YFA), which will support his work on metasurface-based flat optical modulators.
A schematic showing the working mechanism of a spatial light modulator. Credit: Nanfang Yu/Columbia Engineering
“We are looking to demonstrate a new class of planar optical devices called spatial light modulators that are able to mold optical wavefronts into complex shapes and with fast speed,” Yu says. “I am very pleased to receive this significant recognition, which will advance my lab’s research on ‘flat optics’—using strong interactions between light and 2D-structured materials to control light at will.”
Spatial light modulators (SLMs) consist of two-dimensional arrays of “optical antennas” that have sub-wavelength dimensions and are able to actively control the properties of the scattered light waves. These high-speed and light-weight optoelectronic devices are crucial for light detection and ranging, or LIDAR, a technology useful for a wide range of applications, including remote sensing, navigation, and surveillance. SLMs that control mid-infrared light will be particularly helpful in enabling pilots, for instance, to see through strongly scattering optical media such as fog, smoke, and dusty haze.
“Demonstrating high-frame-rate infrared SLMs is an extremely challenging subject,” Yu notes. A high performance optical system requires three key components: light sources, modulators, and detectors. Over the past couple of decades, there have been major advancements in the development of both infrared light sources and detectors, but progress towards fast, electrically tunable infrared SLMs remains limited.
Yu and his PhD students Zhaoyi Li and Adam Overvig plan to realize large modulation of light with high speed by using a hybrid structure of optical antennas integrated with optical materials with electrically tunable optical refractive indices. His key concept is to use tunable materials to shift the optical resonances of the optical antennas so that the properties of the scattered light from the antennas can be altered significantly. His SLMs will consist of a 2D array of such tunable optical antennas, individually controlled by electronics, to generate arbitrary optical wavefronts with desired phase, amplitude, and polarization profiles.
“For the long term, we want to replace all common optical devices and components with their advanced ‘flat’ counterparts, and to substantially miniaturize optical instruments and enhance their performance,” Yu explains. “We will realize this ambition by designing light-matter interaction at the deep subwavelength scale and by learning from design ‘rules’ discovered in nature.”