The Rice SLM chips are essentially nanoscale ribs of crystalline silicon that form a cavity sitting between positively and negatively doped silicon slabs connected to metallic electrodes. The positions of the ribs are subject to nanometer-scale "perturbations" and tune the resonating cavity to couple with incident light outside.
That coupling pulls incident light into the cavity. Only infrared light passes through silicon, but once captured by the SLM, it can be manipulated as it passes through the chip to the other side, according to Xu. The electric field between the electrodes turns the transmission on and off at very high speeds, he said.
Xu said LED screens and micromirror arrays in projectors are both SLMs in which the mirrors rotate. But although the SLM is one of the basic elements of optical systems, their switching speed is limited, he said. Some of their switching speeds can get down to microseconds, which is okay for displays and projectors, he said.
"But if you really want to do information processing, if you want to put data on each pixel, then that speed is not good enough," Xu said.
Crystalline silicon sits between two electrodes in a microscopic antenna-on-a-chip designed by researchers at Rice University. The chip, a spatial light modulator, couples with incident light and makes possible the manipulation of infrared light at very high speeds for signal processing and other optical applications.
Credit: Xu Group/Rice University
According to Xu, the Rice team's device can potentially modulate a signal at more than 10 gigabits per second.
"We think this can basically scale up the capability of optical information processing systems by an order of several magnitudes," Xu said.
The researchers see potential for free-space SLMs in imaging, display, holographic, measurement and remote sensing applications.