Researchers reveal dual function in mainstay photonic component
Researchers at Columbia University have demonstrated that a standard component already widely used in photonic integrated circuits can serve a second, critical function, offering a simple and scalable solution to one of integrated photonics’ most persistent challenges: temperature control.
The team showed that thin-film metallic resistors, commonly used as on-chip heaters to tune photonic devices, can also act as accurate, real-time temperature sensors.
Photonic devices are highly sensitive to temperature fluctuations, with even small changes capable of shifting resonance frequencies and degrading performance.
Until now, monitoring chip temperature has typically required external sensors and additional hardware, creating obstacles for further miniaturisation and large-scale integration.
The Columbia researchers found that the thin-film platinum resistors already integrated into many photonic chips exhibit a strong temperature-dependent resistance, enabling them to function as on-chip resistance thermometers without adding new materials or fabrication steps.
The discovery emerged when the team observed large resistance changes in platinum heaters after modifying a chip’s heat source.
Further investigation revealed non-Ohmic behaviour in the thin-film metal, similar to that seen in tungsten filaments, indicating a strong link between resistance and temperature.
By placing the resistor directly above a high-quality microcavity, the researchers were able to directly measure and stabilise the cavity temperature in real time.
Using this integrated thermometer, the team demonstrated long-term stabilisation of a photonic cavity by frequency-locking a commercial distributed feedback laser, maintaining wavelength stability within a picometer for more than two days.
Such performance is critical for optical communication systems and could be achieved without additional photodetectors or external sensing hardware.
The approach is platform-agnostic and compatible with existing foundry processes, making it applicable to a wide range of photonic devices, including silicon ring modulators already used in commercial data-centre applications.
The researchers also note potential benefits for emerging quantum photonic systems, where precise temperature control is essential and integrated sensing could help reduce system size and complexity.
The work represents a practical step toward more stable, scalable, and commercially viable photonic integrated circuits operating in real-world environments.
