Based on the article written by Altaf Ramji, PCO-TECH Inc., and Evan Eshelman, Impossible Sensing
Operating in environments ranging from climate-controlled labs to the surface of Mars, back-illuminated sCMOS detectors offer high sensitivity, high dynamic range, and low noise, even in low-light conditions. These advanced detectors significantly enhance the capabilities of Raman spectroscopy, a technique widely used for detailed material characterization.
Understanding Raman Spectroscopy
Raman spectroscopy provides detailed insights into a material’s geochemical composition by creating a molecular fingerprint. This technique is not only crucial for material identification but also for measuring properties like crystallinity and stress strain. It involves directing a monochromatic light source, typically a laser, at a sample. The interaction of light with the sample’s molecules causes vibrations that alter the properties of the scattered light, which is then analyzed to determine the sample’s composition based on the Raman shift.
Despite its effectiveness, Raman spectroscopy deals with very weak signals. The scattered light returning from the sample is often extremely faint, necessitating highly sensitive detection methods. This challenge has driven the evolution of detection technologies, with modern back-illuminated sCMOS detectors emerging as superior options.
Limitations of Older Detection Technologies
Traditional Raman spectroscopy systems often relied on photomultiplier tubes (PMTs) or avalanche photodiodes (APDs). PMTs, while extremely sensitive down to single photon counting, are limited by their single-element nature, measuring one spectral peak at a time. This sequential scanning is slow and impractical for many applications, especially those requiring broad area scans and high sensitivity.
Advantages of Back-Illuminated sCMOS Detectors
Back-illuminated sCMOS detectors represent a significant advancement over older technologies, offering several key benefits:
- Higher Quantum Efficiency (QE): These detectors provide higher QE, enhancing the ability to detect low-light signals, such as weak Raman emissions. They are sensitive across a broad spectral range, from ultraviolet (UV) to near-infrared (NIR).
- Broad Spectral Response: Back-illuminated sensors are effective across a wide spectral range, from 190 nm to 1100 nm. This broad response allows them to detect a wide array of signals, making them versatile for various applications.
- Low Dark Current and Homogeneous Imaging: Deep cooling capabilities of back-illuminated cameras result in very low dark current, leading to more homogeneous images and improved detection of weaker signals, even during longer exposure times.
- High Dynamic Range: These detectors can handle a wide range of signal intensities within a single image, eliminating the need for multiple captures to resolve signals of varying brightness.
Application in Planetary Exploration
Impossible Sensing has integrated PCO’s back-illuminated sCMOS cameras into instruments designed for planetary exploration. For example, the pco.edge 4.2 bi camera is used in Raman spectroscopy applications to analyze geochemical compounds on planetary surfaces. Key features of this camera include:
- 2048 x 2048 Resolution: Ideal for high-resolution spectral measurements, enabling the detection of numerous peaks across a spectral window.
- High Quantum Efficiency: With a peak QE of 95% and low noise (less than 1.9 electrons), it ensures accurate and sensitive measurements.
- Speed: Capable of achieving results in a few hundred milliseconds, a significant improvement over older systems that could take minutes or hours.
- Ease of Integration: The pco.edge 4.2 bi’s design and software developer kit (SDK) facilitate quick and seamless integration into various instruments.
Revolutionary Impact on Exploration
The next-generation DiSCO (Dual in-situ Spectroscopy and COring) system by Impossible Sensing, funded by NASA, combines multiple spectroscopic techniques into a single, modular instrument for planetary exploration. Equipped with PCO detectors, DiSCO can perform in-situ, co-registered, high-resolution imaging and core mapping, drastically reducing the resources needed for Raman and LIBS (laser-induced breakdown spectroscopy) measurements.
Conclusion
Raman spectroscopy, enhanced by back-illuminated sCMOS detectors, is entering new frontiers, including space exploration. These detectors provide high sensitivity, dynamic range, and low noise, enabling advanced applications previously thought impossible. From planetary exploration to deep ocean research, the integration of PCO’s back-illuminated cameras is paving the way for groundbreaking discoveries.
RESOURCES
- Basics/principles of Raman spectroscopy https://youtu.be/SsIYDEma_cU and https://youtu.be/qBDtIY5vCIo
- Impossible Sensing is using the pco.edge 4.2 bi in this application:
º https://sbir.nasa.gov/SBIR/abstracts/19/sbir/phase2/SBIR-19-2-S1.07-2925.html
º https://sbir.nasa.gov/SBIR/abstracts/19/sbir/phase1/SBIR-19-1-S1.07-2925.html
Note:
This article was written some time ago. To ensure accuracy and relevance, consult our experts to determine the most suitable spectrometer for performing these measurements currently.
