LDD400

CS-LDTC02 WAVELENGTH | Alldatasheet

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and security fields in the future. interacting with the different energy states of a molecule. be electronic levels, or their neighboring vibronic levels. by the energy-level diagram in Figure 1. Figure 1. Energy-level diagram for Rayleigh scattering. (a) An incoming photon interacts with the medium. (b) The medium gets excited to an intermediate state. (c) The medium de-excites back to the ground state. (d) The scattered photon exits with the same frequency. photons have the same frequency.

applications of SERDS, including mid-surgery diagnoses. are slightly shifted in wavelength (less than a nanometer). Figure 4. Method for obtaining accurate SERDS Raman

1 SERDS probe, that included the light source,

sensing optics, and was fiber coupled to the spectrometer. detectors are still sensitive at this wavelength. combine the two beams into a single output beam. Figure 5. Schematic of handheld SERDS probe. DWL line) is offset for clarity.

drivers and temperature controllers for this application. Figure 6. Illustration of the Y-branch used to control the two independent wavelengths and output power. -1 throughout the whole power range. control locations on the Y-branch. size to enable portability of the SERDS system.

Case Study CS-LDTC02 Rev. A Page 5 © 2017 • Sales & Technical Support: (406) 587-4910 • email: sales@teamWavelength.com • web: www.teamWavelength.com KEYWORDS Raman, scattering, spectroscopy, Shifted Excitation Raman Difference Spectroscopy, SERDS, laser driver, temperature controller, in-situ, near infrared, NIR PRODUCTS USED LDD400, HTC1500

REVISION HISTORY

Document Number: CS-LDTC02 REVISION DATE NOTES A August 2017 Initial Release REFERENCES 1. M. Maiwald, A. Müller, B. Sumpf, "In-situ shifted excitation Raman difference spectroscopy: development and demonstration of a portable sensor system at 785 nm," Proc. of SPIE 10054, Advanced Biomedical and Clinical Diagnostic and Surgical Guidance Systems XV, 1005409 (2017). 5. MIT Spectroscopy - Research in Biomedical Optics, "Non-Invasive Measurement of Blood Analytes using Raman Spectroscopy," http://web.mit.edu/spectroscopy/research/biomedresearch/Methods.html USEFUL LINKS

• LDD400 Product Page
• HTC1500 Product Page SUMMARY Researchers from Berlin designed and built a portable measurement system to make field measurements. The system utilized Shifted Excitation Raman Difference Spectroscopy (SERDS), which is a variation of Raman spectroscopy. In addition to the portability, the stability of the laser system, driven by four LDD400s and temperature controlled by an HTC1500, was found to be better than the resolution of the spectrometer being used to analyze the signal. Thorough stability tests were performed, varying the temperature of the case, the injection currents, and the power output. Raman spectroscopy, dealing with very small energy changes, can have difficulties if the background signal is high. SERDS, by collecting two spectra, and taking the difference between them, allowed the unwanted background to be effectively discarded. With the background greatly reduced, and the Raman signal resolved, the researchers studied apple leaves with great resolution in the field. Chlorophyll and cartenoid lines could be resolved with the leaves still on the tree. RESULTS With the stable, portable SERDS system, the researchers moved their measurements from the lab to the field. They took their system to an apple orchard in Switzerland, where they studied leaves on the apple trees. Utilizing two laser wavelengths around 785, separated again by approximately 10cm -1, the researchers performed their SERDS experiment on the apple leaves. In the initial Raman spectra, the background noise is enormous due to the ambient daylight conditions, and atmospheric absorption. Only a single Raman line is discernable in the original spectra. After subtracting the two initial spectra, and reconstructing the SERDS Raman spectra, the researchers found an 11- fold improvement on the signal-to-noise ratio of the Raman line that was visible previously. In addition to clarifying that Raman line, the reconstructed SERDS spectrum has minimal background noise, and is able to resolve Raman lines of cholorophyll and carotenoids, which match known values. For plots of the results, see the full paper here.