Cryogenic lasers could solve the data bottleneck in next-generation infrared imaging

Infrared imaging is moving into a new technical phase. Higher-resolution infrared focal plane arrays (FPAs), faster frame rates and improved sensitivity are expanding what thermal imaging systems can do, from astronomy and scientific instrumentation through to industrial monitoring, environmental sensing and advanced machine vision. Yet this progress creates a less glamorous but increasingly important engineering problem: how to move very large volumes of data out of sensors operating at cryogenic temperatures without adding unwanted heat. A new study from researchers at the University of Illinois Urbana-Champaign, published in IEEE Photonics Technology Letters, suggests one answer may be to replace conventional electrical links with cryogenic vertical-cavity surface-emitting laser, or cryo-VCSEL, optical interconnects.

Infrared FPAs convert infrared light into electrical signals to create thermal images. Many high-performance infrared detectors are cooled to cryogenic temperatures to reduce noise and improve sensitivity. The complication is that modern FPAs increasingly require data rates above 100 gigabits per second. Traditional copper-based electrical interconnects can provide bandwidth, but they also conduct heat into the cold sensor environment. This thermal leakage increases noise, raises cooling demand and adds to system-level power consumption. In cryogenic instrumentation, even small heat loads matter because removing heat at very low temperatures is energetically expensive.

Carrying data by electronic means

The Illinois team investigated whether optical links could overcome this limitation. Instead of carrying data electronically through copper conductors, optical interconnects encode information using light and transmit it through optical fibre. The device at the centre of the study is a VCSEL, a semiconductor laser that emits light vertically from the surface of the chip rather than from its edge. VCSELs are attractive because they are compact, energy efficient, compatible with array fabrication and already widely used in short-reach optical communications. The novelty here is operation at cryogenic temperatures, specifically across 77 K to 120 K, which corresponds to minus 196°C to minus 153°C.

The reported performance is notable: The cryo-VCSEL achieved a 3-dB modulation bandwidth exceeding 50 GHz at low bias currents below 4 mA. The researchers demonstrated 112 Gb/s per lane pulse amplitude modulation, and extended operation up to 138 Gb/s per lane using PAM-4 signalling. The study also reported transmitter and dispersion eye closure quaternary, or TDECQ, values of 3.42 dB at 77 K and 4.15 dB at 120 K, meeting IEEE standards for short-reach multimode communication. Energy consumption was estimated at approximately 68 femtojoules per bit at 77 K and 60 femtojoules per bit at 120 K.

PAM-4 is important because it allows each transmitted symbol to carry two bits of information by using four amplitude levels rather than the two levels used in conventional on-off signalling. This increases data throughput without requiring a proportional increase in modulation frequency. For imaging systems, the benefit is clear: multiple high-speed optical lanes could move large volumes of sensor data away from the detector while keeping the thermal load low. This is especially relevant as infrared FPAs become larger and faster.

The cryogenic aspect is more than an operating condition. Semiconductor laser behaviour changes with temperature. Parameters such as threshold current, output power, modulation response and efficiency can shift significantly as the device is cooled. In this study, the VCSEL maintained a smooth relationship between input current and optical output across the tested temperatures. TechXplore’s summary of the work reported a maximum optical output of 13.35 mW at 77 K and 10.42 mW at 120 K, with output decreasing as temperature increased.

Cryogenic computing: Chilling for the future

The immediate application is infrared imaging. FPAs are used in areas such as surveillance, astronomy and industrial monitoring, where thermal contrast can reveal information invisible to conventional cameras. However, the broader implication is that optical interconnects may become essential wherever electronics must communicate across a cryogenic boundary. This includes scientific detectors, quantum technologies, superconducting electronics and cryogenic computing platforms. The author Liu notes that cryo-VCSEL links may provide an interface between room-temperature peripherals and cryogenic electronics.

This matters because cryogenic computing is no longer a niche curiosity. Quantum computers, superconducting digital circuits and ultra-sensitive detectors all face the same input-output challenge. The cold stage must be isolated thermally, while still receiving control signals and sending data back to room-temperature systems. Conventional wiring becomes a bottleneck because every wire is also a heat path. Optical fibre, by contrast, can offer high bandwidth with reduced conductive heat leakage.

The economic angle is also important. High-performance infrared imaging systems are expensive partly because of cooling requirements, integration complexity and data-handling infrastructure. If optical interconnects reduce cooling load and simplify high-speed signal extraction, they could lower system-level costs or enable higher performance within the same power budget. This could benefit industrial inspection, remote sensing, autonomous systems, scientific imaging and semiconductor metrology.