Efficient programming of integrated small optical sources is an important part of photonic technologies. However, as the density of laser arrays increases, the miniaturization and scalability of laser control using an electric drive is being pushed to its limits.

Scientists have developed a new all-optical method for driving multiple highly dense nanolaser arrays. These nanolaser arrays – in which the lasers are spaced just 18 microns apart – can be fully controlled and programmed with light from a single optical fiber. The approach could enable chip-based optical communication links that process and move data faster than current electronic devices.

Korea University research team leader Myung-Ki Kim said: “The development of optical links equipped with high-density nanolasers would improve information processing in the data centers that move information across the Internet. This could enable the streaming of ultra-high-definition movies, enable large-scale interactive online encounters and games, accelerate the expansion of the Internet of Things, and provide the high-speed connectivity needed for big data analytics.”

“Optical devices integrated on a chip are a promising alternative to electronically integrated devices, which are struggling to keep up with current data processing demands. By eliminating the large and complex electrodes typically used to drive laser arrays, we have reduced the overall size of the laser array while eliminating the heat generation and processing delays associated with electrode-based drivers.”

The new nanolasers can be applied to optical integrated circuits, which use light to detect, produce, transmit and process data on a microchip. Optical waveguides are used in optical circuits instead of the thin copper wires in electronic chips because they allow significantly greater bandwidths while producing less heat. However, new approaches are needed to effectively drive and regulate their nano-sized light sources as the scale of optical integrated circuits is rapidly approaching the nanometer regime.

Lasers require energy to emit light, which is provided by a process known as pumping. This is commonly done for nanolaser arrays where a pair of electrodes is used for each laser in an array, which consumes a lot of space and energy on the chip and slows down processing. The scientists swapped these electrodes for a special optical driver that uses interference to create customizable light patterns to get around this critical limitation. An optical cable with nanolasers printed on it carries this pump light.

To illustrate this strategy, the scientists created many photonic crystal nanolasers spaced 18 microns apart using a high-resolution transfer printing process. A 2 micron diameter microfiber optical surface was covered with these arrays. The interference pattern had to be perfectly aligned with the nanolaser arrays to do this. The interference pattern can also be changed by varying the pulse width and polarization of the main beam.

The studies showed that the architecture made it possible to drive several nanolaser arrays with light passing through a single fiber. The results showed that the printed nanolaser arrays could be fully controlled by the pump beam interference patterns and agreed well with numerical calculations.

kim said, “Our all-optical laser drive and programming technology can also be applied to chip-based silicon photonics systems, which could play a key role in the development of chip-to-chip or on-chip optical interconnects. However, it would be necessary to prove how independently the modes of a silicon waveguide can be controlled. If this is possible, it would be a huge step forward in the advancement of on-chip optical interconnects and optical integrated circuits.”

Magazine reference:

  1. Da In Song, Aran Yu, Polnop Samutpraphoot, Jungmin Lee, Moohyuk Kim, Byoung Jun Park, Alp Sipahigil, Myung-Ki Kim. Three-dimensional programming of nanolaser arrays through a single optical microfiber. Optics, 2022; 9 (12): 1424 DOI: 10.1364/OPTICA.471715