IEEE Study Reveals Energy-Efficient High-Speed Cryogenic-VCSEL Optical Interconnects

Infrared focal plane arrays (FPAs) are image sensors, widely used in thermal imaging systems across various fields. Future advancements in FPAs are expected to require high data rates, which can cause heat leakage from electrical interconnects into FPAs, increasing noise and raising cooling requirements. In a new study, researchers demonstrated cryogenic vertical-cavity surface-emitting laser (VCSEL)-based optical interconnects that can achieve high-speed communication while reducing thermal leakage and power consumption.

FPAs are image sensors that convert infrared light into electrical signals to produce real-time thermal images and are widely used in applications such as surveillance, astronomy, and industrial monitoring. Advances in cryogenic FPAs have enabled higher resolution, sensitivity, and faster imaging, but they also require data rates exceeding 100 gigabits per second. Conventional electrical interconnects used to support these demands increase heat load through copper connections, which can leak into FPAs, raise noise, and increase cooling requirements and power consumption.

Against this backdrop, a new study published in IEEE Photonics Technology Letters on March 27, 2026, explored cryogenic vertical-cavity surface-emitting lasers (cryo-VCSELs) for high-bandwidth optical interconnects in FPAs. “Optical interconnects can reduce heat transfer while maintaining high data rates. Cryo-VCSELs offer a small footprint, high bandwidth, and low energy-per-bit operation at cryogenic temperatures,” explains author Liu from the University of Illinois Urbana-Champaign, USA. 

VCSELs are semiconductor laser diodes that emit a cylindrical, high-quality laser beam perpendicular to the surface of the chip and are known for their low power consumption. In this study, the researchers developed a VCSEL with a 4.5-micrometer oxide aperture and a half-wavelength cavity and evaluated its performance for PAM-4 data transmission over a temperature range of 77 K to 120 K.

The experiments showed that the device maintained a largely linear and smooth relationship between input current and light output. The VCSEL achieved a maximum optical power output of 13.35 milliwatts (mW) at 77 K and 10.42 mW at 120 K, with output decreasing as temperature increased.

The device also demonstrated strong high-frequency performance at both temperatures, achieving a 3-decibel modulation bandwidth exceeding 50 gigahertz (GHz) while maintaining low energy consumption. Notably, the researchers demonstrated data transmission rates of up to 138 Gb/s per lane using PAM-4 modulation while meeting IEEE standards for short-reach multimode communication. The system also supported 112 Gb/s per lane with low signal distortion and operated with low energy consumption of about 60–68 fJ per bit.

“These results demonstrate that cryo-VCSEL optical links can provide a cost-effective solution for high-speed data communication in FPAs and may also enable applications in cryogenic computing as an interface between room-temperature peripherals and cryogenic electronics,” remarks Liu.

Overall, the study highlights the potential of cryo-VCSEL-based optical links as a practical solution for high-speed, energy-efficient data communication in low-temperature environments.