Advancing Single-Photon Sensing Image Sensors to Enable the Search for Life Beyond Earth

A team sponsored by NASA advances the additional detection technology for the detection of complementary metal-oxide (CMOS) (CMOS) which will allow future spatial missions of the NASA astrophysics to look for life on other planets. As part of their detector maturation program, the team characterizes the sensors before, during and after exposure to high energy radiation; develop new reading methods to mitigate the damage induced by radiation; And simulate a prototype of CMOS pixels near infrared capable of detecting individual photons.

Are we alone in the universe? This secular question has inspired scientific exploration for centuries. If life on other planets evolves in the same way as life on earth, it can print its presence in the known atmospheric spectrals aspiratory. They include absorption and emission lines in the spectrum produced by oxygen, carbon dioxide, methane and other molecules that could indicate conditions that can support life. A future mission of NASA astrophysics, the observatory of habitable worlds (HWO), will seek to find biosignatures in ultraviolet, optics and infrared (nir) spectra of exoplanet atmospheres to seek evidence that life can exist elsewhere in the universe.

HWO will need very sensitive detection technology to detect these low biosignatures on remote exoplanets. The complementary image of metal metal-oxide (SPSCMOS) is a promising technology for this application. These silicon -based sensors can detect and solve individual optical wavelength photons using a high -capacity -to -cap -saving floating node. They operate effectively on a wide range of temperatures, including at room temperature. They have an almost zero reading noise, are tolerant of radiation and generate very unwanted signal, like a dark current. When cooled at 250 k, the dark current falls to a single electron every half hour. If the reading noise or the dark current are too high, the sensor will not detect the weak signals that the biosignatures produce.

A research team from the Rochester Institute of Technology (RIT) Center for Detectors (CFD) accelerates the preparation of these SPSCMOS sensors for use in space missions thanks to maturation programs of the technology of detectors funded by the strategic technology of NASA astrophysics and the stresses of early innovations. These development programs include several key objectives:

• Characterize the performance metrics of the critical detector such as dark current, quantum efficiency and noise reading before, during and after exposure to high -energy radiation
• Develop new reading methods for these sensors in order to mitigate the effects from short and long -term damage
• Design a new NIR version of the sensor using computer -assisted design software (TCAD) Technology

The SPSCMOS sensors work similarly to traditional CMOS image sensors but are optimized to detect individual photons – an essential capacity for ultra -sensitive space observations, such as the measurement of gases in the atmospheres of exoplanets. Inbound photons enter the sensor and generate free loads (electrons) in the sensor material. These charges accumulate in a pixel storage well and end up transferring to a component with a low capacity called a node of floating diffusion (FD) where each free load causes a large and resolved tension shift. This voltage shift is then scanned to read the signal.

Experiments that measure the performance of the sensor in an environment relevant to space use a vacuum dew and a thermal control support to allow precise adjustment of the temperature of the sensors. The DEWAR allows tests under conditions that correspond to the expected thermal environment of the HWO instrument, and can even cool the sensor and its circuits on chip at colder temperatures than any previous test reported for this family of detectors. These tests are essential to reveal performance limitations with regard to detector measurements such as dark current, quantum efficiency and reading noise. As the temperatures change, the electrical properties of the circuits on the chip can also change, which affects the reading out of charge in a pixel.

The environment -rich environment for HWO will cause temporary and permanent effects in the sensor. These effects can corrupt the measured signal in a pixel, the blocking of the interruption sensor and digital logic, and can cause cumulative damage that gradually degrades the performance of the sensor. To alleviate the loss of sensitivity to the detector throughout a lifespan of the mission, the RIT team develops new reading methods that are not available in commercial CMOS. These personalized modes sample the signal over time (a “ramp” acquisition) to allow the detection and elimination of cosmic ray artefacts. In a mode, when the system identifies an artifact, it segments the signal ramp and selectively makes the segments to rebuild the original signal – preserving the scientific data which otherwise would be lost. In addition, a real -time data acquisition system monitors the energy consumption of the detector, which can change the accumulation of damage throughout a mission. The acquisition system records these changes and communicates with the electronics of the detector to adjust voltages and maintain nominal operation. These attenuation strategies for radiation damage will be assessed during a number of test programs in ground radiation facilities. Tests will help identify the unique failure mechanisms that have an impact on SPSCMOS technology when exposed to an equivalent radiation at the expected dose for HWO.

While the existing SPSCMOS sensors are limited to detect visible light because of their silicon -based design, the RIT team develops the first photon nir photodiode in the world based on the architecture used in optical sensors. The design of the photodiode begins as a simulation in the TCAD software for Moddle the optical and electric properties of CMOS architecture with low capacity. The model simulates the light circuits using the material of silicon and mercury of downward cadmium (HGCDTE or MCT) to determine to what extent the pixel would measure the photo load if a semiconductor foundry made it physically. It has 2D and 3D devices structures that convert light in electric load, and circuits to control load transfer and signal reading with virtual probes that can measure the flow of current and electric potential. These simulations help to assess key mechanisms such as conversion of light into electrons, storage and transfer of electrons and output voltage of the photodiode sampling circuit.

In addition to laboratory tests, the project includes performance assessments in a ground telescope. These tests allow the sensor to observe astronomical targets which cannot be fully reproduced in the laboratory. Star fields and diffuse nebulae question the complete signal chain of the detector under real-calfs of the real sky with low flow levels, aberrations dependent on the field and variable vision conditions. These observations help identify performance limitations that may not be apparent in controlled laboratory measurements.

In January 2025, a team of researchers led by doctoral student Edwin Alexani used a camera based in SPSCMOS at the Cek Mees Observatory in the county of Ontario, New York. They observed the M36 star cluster to assess the photometric accuracy of the sensor and the bubble nebula in a H-Alpha H-Band filter with narrow band. The dark current measured and the reading noise were consistent with the laboratory results.

The team has observed photometric reference stars to estimate quantum efficiency (QE) or detector capacity to convert photons into signal. The calculated QE agreed with laboratory measures, despite the differences in calibration methods.

The team also observed the Starlink -32727 satellite while it was in the field of vision of the telescope and measured a negligible persistent load signal – which can remain in the pixels of the detector after exposure to a light source. Although the satellite briefly produced a light sequence through several pixels due to reflected sunlight, the average latent load in the affected pixels was only 0.03 th^–/ PIX – Well below the basin sky and the sensor reading noise.

While NASA progresses and matures the HWO mission, SPSCMOS technology promises to change the situation for exoplanet and general research of astrophysics. These sensors will improve our ability to detect and analyze the distant worlds, bringing us closer to one of the deepest questions of humanity: are we alone?

For more details, see the entry of this project on NASA Techport.

Project (s): s): Dr. Donald F. Figer, Future Photon Initiative and Center for Detectors, Rochester Institute of Technology (RIT), supported by engineer Justin Gallagher and a team of students.

Organization (s) Sponsor :: Division of NASA astrophysics, Strategic Astrophysical Technology Technology Program (SAT) and NASA Space Technology Direction (STMD), Innovations Program (ESI)