Close-up of the chip-scale isolator. Credit: Hannah Kleidermacher
Lasers are powerful optical tools used in a wide range of instruments and applications across various industries including laboratory equipment, manufacturing equipment and optical communications. The light emitted by lasers can reflect back onto the laser and destabilize it, which requires the use of isolators to prevent this unwanted feedback; however, such isolators are often large devices that rely on magnetism, making them less feasible to integrate into smaller electronics such as computer circuitry. Now, researchers at Stanford University have developed a new, chip-scale isolator that can be easily integrated into thin, semiconductor-based materials and could help enable next-generation computing technologies.
The nanoscale isolator is shaped like a ring and made from silicon nitride. A major advantage of the isolator is that it is passive, not requiring any external inputs, magnetics or additional complicated electronics that could cause interference and make devices too bulky for integrated photonics applications. When a laser beam is emitted, it enters the ring and the photos spin around the isolator in a clockwise direction, while the back-reflected light travels around the ring in the opposite direction.
“The laser power that we put in circulates many times and this allows us to build up inside the ring. This increasing power alters the weaker beam, while the stronger one continues unaffected,” explained co-first author Geun Ho Ahn. “The reflected light, and only the reflected light, is effectively canceled.”
The primary laser is able to exit the ring and be isolated in the desired direction while the reflected light stops resonating and is prevented from destabilizing the laser. Another advantage of the ring isolator is the fact that it is constructed from a common, well-known semiconductor-based material, meaning it can be easily manufactured using existing semiconductor processing technologies as well as integrated into thin electronic components. The team was also able to couple two ring isolators in a cascade to improve the performance of the system. This research was published in Nature Photonics.
“Next steps include working on isolators for different frequencies of light,” said co-author Kasper Van Gasse. “As well as tighter integration of components at chip scale to explore other uses of the isolator and improve performance.”
Potential applications of the isolator include not only transforming everyday computer technologies, but also enabling advanced applications such as quantum computing.