Researchers at Sandia National Laboratories in the United States have used silicon photonic microchip components to perform a quantum sensing technology called atomic interferometry. This is an ultra-high-precision method for measuring acceleration and is the latest achievement in the development of a "quantum compass" that can navigate without a global positioning system (GPS) signal. The research paper was published in the latest issue of Science Advances.
Smartphones, fitness trackers or virtual reality devices have tiny sensors inside to track position and movement. The "upgraded" version of the same technology, which is the size of a grapefruit and a thousand times more accurate, uses GPS to help navigate in areas with higher needs. As technology advances, the size and technical costs of such high-precision sensors are being greatly reduced.
The new high-performance silicon photonic modulator is a device that controls light on a microchip. Each atom interferometer requires a laser system, which in turn requires a modulator.
Typically, an atom interferometer as a sensor system needs to occupy a small room. A complete "quantum compass" (quantum inertial measurement unit) requires six atom interferometers. The team succeeded in replacing a large, power-hungry vacuum pump with a vacuum chamber the size of an avocado, and integrating multiple components into a single, rigid device.
The new modulator is the heart of a laser system on a microchip. It can withstand strong vibrations and will replace conventional laser systems, which are often the size of a refrigerator. Lasers perform multiple tasks in an atom interferometer. The team used four modulators to change the frequency of a single laser to perform different functions.
Modulators often produce unwanted echoes, called sidebands, which need to be suppressed. The team's suppressed carrier single-sideband modulator reduces these sidebands by an unprecedented 47.8 decibels, reducing the sideband intensity by nearly one-hundred-thousandth of the original.
Cost was previously a major obstacle to deploying quantum navigation devices. Now, the team can make hundreds of modulators on an 8-inch wafer. Miniaturizing large and expensive components into silicon photonic chips helps reduce costs.
