Japan’s NICT and Sony co-develop ‘first’ surface-emitting laser for communication

11 Jun 2025

Using quantum dots as gain medium; based on NICT crystal growth and Sony processing.

Optical communication technologies require large-capacity data transmission with minimal power consumption. Vertical-cavity surface-emitting lasers (VCSELs) have attracted significant attention as a key technology that addresses these requirements.

However, VCSELs typically operate in the near-infrared region, at wavelengths of 850 or 940 nm. Developing VCSELs that operate at the long wavelength of 1,550 nm has long presented significant technical challenges.

Now, Japan’s National Institute of Information and Communications Technology (NICT), in collaboration with Sony Semiconductor Solutions, has developed what they describe as “the world’s first practical surface-emitting laser that employs quantum dots as the optical gain medium for use in optical fiber communication systems.”

The partners stated that the achievement was enabled by a combination of NICT’s high-precision crystal growth technology and Sony’s advanced semiconductor processing technology. The surface-emitting laser developed incorporates quantum dots as light-emitting materials.

Their joint announcement stated, “this approach not only facilitates the miniaturization and reduced power consumption of light sources in optical fiber communications systems but also offers potential cost reductions through mass production and enhanced output via integration.” The results of this research have been published in Optics Express.

Respective technical details

NICT developed the first core technology: a high-precision crystal growth method for compound semiconductors using molecular beam epitaxy. Fabricating a VCSEL requires growing a highly reflective semiconductor multilayer film (a DBR – Distributed Bragg Reflector) to enhance light intensity; however, fabricating DBRs that operate at 1,550 nm has been challenging because the combination of materials that can be grown is limited.

Therefore NICT developed a technology that can precisely grow DBR by strictly controlling the ratio of materials in the crystal growth and achieved a semiconductor DBR with a high reflectivity exceeding 99% even at 1,550 nm. In addition, strain-compensation techniques were applied to the VCSEL production to accurately cancel the internal crystal strain that occurs around the quantum dots, thereby significantly increasing the density of the quantum dots and improving the light-emitting performance.

Sony contributed to the second core technology: a device design and fabrication process that enables highly efficient current injection employing a tunnel junction. VCSELs emit light perpendicular to the wafer surface; therefore conventional electrode placement obstructs light extraction. Sony addressed this by implementing a tunnel junction structure that permits efficient current flow while facilitating light extraction employing a precise device process.

The NICT-Sony statement said, “Through the integration of these two technologies, we succeeded in lasing VCSELs using quantum dots at 1,550 nm as a light-emitting material with a small current of 13 mA (low threshold). Furthermore, polarization fluctuations were eliminated, resulting in a stable output.”

Future prospects

The statement continued, “We aim to conduct advanced technical studies on quantum-dot-based VCSEL technology to further enhance the capacity and reduce power consumption in optical fiber communication systems beyond the 5G era. Concurrently, we will undertake efforts to promote social deployment of this technology.”