03/11/2019
The ability to control light with electronics is a critical part of advanced photonics, a field with applications that include telecommunications and precision time-keeping. But the limits of available optical materials have stymied efforts to achieve greater efficiency.
Researchers at Yale, though, have developed a device that combines mechanical vibration and optical fields to better control light particles. The device has demonstrated an efficient on-chip shaping of photons enabled by nanomechanics driven at microwave frequencies. Led by Hong Tang, the Llewellyn West Jones, Jr. Professor of Electrical Engineering, Applied Physics & Physics, the results of their work are published today in Nature Photonics.
Currently, the most common technique for manipulating photon frequency is with what’s known as nonlinear optical effects, in which a strong laser essentially acts as a pump, controlling the color and pulse shape of a signal photon by providing extra photons to mix with the original one. The effect is weak, though, so the process requires a very strong laser, which creates “noise" - the loss of certain quantum properties.
To break beyond these limits, the Yale researchers have created a device that consists of a series of waveguides - structures through which microwaves are directed. Light and microwave are sent through the device, and the light wends its way through alternating suspended and clamped waveguides on a single chip. This creates a positive and negative effect, corresponding to the microwave, which always has a positive and a negative component. The light spirals in each of the waveguides to prolong the interaction and maximize efficiency.
“The deeper the modulation, the better,” Tang said, "and you can have better control of the photon.”
Mechanical vibrations modulate the optical phase in each suspended waveguide spiral. The mechanical vibrations essentially ‘shake’ the photons, dispersing them as if they were grains of sand. This accumulates to generate what’s known as deep phase modulation.
Previously, the Tang lab had created a single waveguide device. With this new device, the alternating positive and negative waveguides dramatically boost efficiency.
Other contributors to the paper include lead author Linran Fan, Chang-Ling Zou, and Na Zhu.
