Photonic Thermometry

Summary

Photonic Thermometry is a cutting-edge research program at NIST that aims to break the fundamental limitations of electrical resistance-based thermometry and open new horizons for temperature measurement science. The main three goals of Photonic Thermometry are: (1) to realize a new field-deployable, chip-scale, photonic integrated circuit-based quantum SI (qSI) sensor and primary standard for temperature; (2) to revolutionize the realization and dissemination of temperature by reducing the temperature calibration chain sensor ownership cost; and (3) to create an integrated nanophotonics platform to enable new sensing applications. Being a synergy of various research fields, the program combines recent advances in state-of-the-art nanofabrication, integrated nanophotonics, high-performance optomechanical devices, and optical frequency metrology. Photonic Thermometry is part of the NIST on a Chip (NOAC) program.

Description

Why do we need reliable temperature metrology?

Temperature, the second most measured physical property after time and frequency, is indispensable to innumerable industries, military services, medicine, climate, and weather forecasts – precise, accurate, and rapid temperature metrology enables much of the modern technology we depend on. The operation of well-accepted conventional temperature sensors, such as platinum resistance thermometers (PRTs), is based on a temperature-dependent resistance measurement of a strain-free metal wire or thin film. Although these sensors are often the best option available, they are sensitive to environmental conditions and mechanical shock and may drift over time. Photonics-based temperature sensors have the potential, without reduction in performance, to bypass these limitations and avoid costly and disruptive recalibration of sensors.

Figure 1. The ultra-sensitive silicon photonic thermometer (SPoT) developed at NIST is a potential candidate to replace the Standard Platinum Resistance Thermometers (SPRTs), the state-of-the-art resistance temperature sensors currently used to disseminate the International Temperature Scale of 1990. A. Fiber-coupled SPoT chip. B. Scanning electron microscope (SEM) image of one of the SPoT’s designs – silicon nanobeam photonic crystal cavity photonic resonator. C. SPoT’s optical transmission spectrum. The resonant frequency is temperature-dependent. Optical frequency metrology can provide high-precision measurements of temperature.

Credit: NIST

Why photonic thermometry?

Photonic thermometry has the potential to outperform the state-of-the-art Standard Platinum Resistance Thermometers (SPRTs) that are currently used to disseminate the International Temperature Scale of 1990. Furthermore, photonic integrated circuit (PIC) technology gives multiple advantages such as low cost, weight, power consumption, manufacturing scalability, microscale sensor’s footprint, fast response time, field-deployability, and near-immunity to electromagnetic interference. Finally, photonic thermometry can enable sensors that can be deployed in various settings ranging from controlled laboratory conditions to a noisy factory floor to harsh environments.

Main research directions of the Photonic Thermometry program

The NIST Photonic Thermometry program is pursuing three interrelated goals.

1. We are developing ultra-sensitive photonic thermometers (SPoTs) based on a silicon-on-insulator (SOI) platform (Figure 1). These devices exploit the thermo-optic effect, translating thermal variations into changes in silicon's refractive index. Microfabricated silicon photonic resonators, such as photonic crystal cavities, ring and disk resonators, act as optical filters whose spectral characteristics can provide a sensitive measure of temperature. The SPoT technology has the potential to displace traditional resistance-based sensors in many existing applications and can open new frontiers in sensing and metrology.
2. In parallel, we are developing an optomechanical device that can measure thermodynamic temperature. This nanoscale device senses the thermally driven Brownian motion of a nanomechanical resonator—a quantity determined by the absolute temperature of the sample. This motion is read out with a cavity-enhanced optical probe. The thermal Brownian motion can be calibrated using the quantum fluctuations of the mechanical resonator so that the system can serve as an on-chip photonic primary standard.

Combining SPoT and an optomechanical device on the same SOI photonic chip can enable a sensor and primary standard in one device. Such thermometers have the potential to supplant the International Temperature Scale of 1990.

3. Finally, we are developing a photonics-based platform that leverages advances in photonic thermometry, optical frequency metrology, and nanofabrication to enable novel sensing applications, including current work in photonic humidity, photonic dosimetry (spun off as a separate NOAC project), and chip-scale AC-DC transfer standard.

Patents and Patent Applications

• U.S. Patent 2024/0133746 A1, Photonic thermometer module assembly and performing photonic thermometry, N.N. Klimov, T.K. Herman, Z. Ahmed (2024)
• U.S. Patent 2024/12,066,741 B2, Photonic AC-DC equivalence converter and performing equivalence, N.N. Klimov, J. Hagmann, S. Cular (2024)
• U.S. Patent Application 18/625,927, High-precision photonic readout and performing high-precision photosensing, K.O. Douglass, N.N. Klimov, A. Rao (2024)
• U.S. Provisional Patent Application 63/669,291, Photonic article 200 and making a photonic article, N.N. Klimov, G. Holland, D. Westly (2024)
• U.S. Patent Application 18/625,879, Optomechanically calibrated photonic thermometer and calibrating a photonic thermometer, D. Barker, N.N. Klimov, T. Purdy (2024)
• U.S. Patent Application 2023/0032022, Photonic bolometer and performing photonic bolometry, N.N. Klimov, N.A. Tomlin, C.S-Y. Yung (2023)
• U.S. Patent 11,422,101 B2, Photonic quantum dew point sensor, T. Herman, N.N. Klimov (2022)
• U.S. Patent 10,955,617B2, High-resolution photonic thermometer article, 
  N.N. Klimov, K.O. Douglass, Z. Ahmed (2021)
• U.S. Patent 10,718,872B2, Photonic dosimeter and process for performing dosimetry, R. Tosh, Z. Ahmed, N.N. Klimov, R. Fitzgerald (2020)
• U.S. Patent 10,782,421B2, Photonic calorimeter and process for performing calorimetry. 
  R. Tosh, Z. Ahmed, N.N. Klimov, R. Fitzgerald (2020)
• US Patent 9,726,553, Optical temperature sensor and use of same, Z. Ahmed, S. Semancik, J.M. Taylor, J. Fan, M. Hafezi, H. Xu, G. Strouse (2014)

Major Accomplishments

• Developed in-house fabrication (from photonic chip design, nanofabrication, to chip packaging) of ultra-sensitive silicon-on-insulator photonic thermometers
• Demonstrated sub-10 µK temperature resolution of photonic thermometers
• Designed an assembly module that accommodates a fiber-coupled photonic thermometer. The module is compatible with measurements in fixed-point cells and other ITS-90 infrastructure.
• Demonstrated operation of packaged photonic thermometers in a wide temperature range from 77 K up to 500 K
• Developed a method for photonic optical bonding compatible with extreme environments: high ionizing radiation (> 1 MGy), deep cryogenic (< 4 K), and high vacuum (> 8´10-6 Pa). We also showed that our approach is readily adaptable to high-temperature applications (> 900 K).

OPPORTUNITIES

We are seeking partners from the U.S. private sector, national laboratories, and academia to join us in developing cutting-edge measurement technologies that will be incorporated into real-world tools and revolutionize the metrology landscape.

If you are interested in joining our team as a Collaborator, Visiting Scientist, Postdoctoral Fellow, or Graduate Student, please contact us for more information.