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  • Raman Spectroscopy for Research and Industry

Jun 24, 2013
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Additional Questions and Answers from the Webinar are below:

Speakers to include:

David J. Brady, Duke University

Computational and Compressive Raman Spectroscopy

"Computational" Raman spectroscopy codes illumination and detection to improve quantum efficiency, enable feature-specific measurement and reduce system size, weight, power and cost. This talk reviews coded aperture, multiwavelength and diffuse illumination Raman system design for ultraviolet, visible and SWIR systems. Brady will also discuss compressive sampling for infrared Raman spectroscopy.

David J. Brady is the Michael J. Fitzpatrick Endowed Professor of Photonics at Duke University, where he leads the Duke Imaging and Spectroscopy Program. Brady was awarded the 2013 SPIE Dennis Gabor Award in recognition of his "development of compressive holographic and tomographic imaging systems." Brady is a graduate of Caltech and was on the faculty of the University of Illinois in Urbana-Champaign before joining Duke in 2001. He is a co-founder of Distant Focus Corp., which builds camera arrays, Centice Corp., which builds Raman spectrometers, Applied Quantum Technologies, which builds computational imaging systems and Aqueti, which builds gigapixel cameras. Brady is the author of "Optical Imaging and Spectroscopy," and is a Fellow of IEEE, SPIE and OSA.

Dr. Prasant Potuluri, CEO and co-founder of Centice

Review of Key Applications of Raman Spectroscopy

Raman spectroscopy has grown significantly over the past decade and is being used for a wide range of applications. We will review some of the applications including identification of narcotics and explosives, counterfeit drug detection, quality control, raw material identification and manufacturing process improvements. We will also discuss some limitations of Raman spectroscopy and opportunities for improvements.

Dr. Prasant Potuluri is CEO and co-founder of Centice. He has been instrumental in launching multiple products from the company's Raman spectroscopy and coded aperture spectroscopy technologies including the Mobile Field Lab-3000 (MFL), a narcotics identification system. Dr. Potuluri obtained a PhD from Duke University, an MBA from North Carolina State University, an MS from University of Illinois at Urbana Champaign and a bachelor's degree in Engineering Physics from Indian Institute of Technology, Bombay.

Additional Questions and Answers from the Webinar


1. Is possible to build a low-cost and embedded Raman spectrometer for automotive applications? Yes, sensitivity required for such a device depends on the specific application.

2. Is it possible to use a Linear Variable Filter instead of a spectrograph or grating? Yes depending on the resolution requirements.

3. Is the trace detection (ppm) possible with Raman spectroscopy? Yes, with additional techniques like Surface enhanced Raman spectroscopy.

4. What is the advantage of Raman versus NIR spectroscopy regarding to the identification of illicit narcotics and explosives? Libraries with Raman can be large due to their sharp and narrow fingerprints. NIR fingerprints are generally broader and may not offer discrimination across a large library set

5. Can mixture analysis give a quantifiable percentage of each component within the measured sample? Yes, it can provide relative ratio based on each component's Raman scattering strength ( not absolute strength, however these two can theoretically be correlated).

6. For phthalate example, your chart says LOD of 1 to 2%. Based on the spectra showed, the peaks in the mixture were quite low. Are you saying that the phthalate can be actually identified at these levels, or just detected? LOD is at 1-2%, however limit of quantification (LOQ) may be a bit higher than that.

7. Raman spectroscopy be used for characterization of nanostructures such as gold or silver nanorods/nanowires? What about semiconductor nanostructures? Raman analysis of nano structures might use a Raman active molecule coupled to the nano particles to characterize resonances and field structures. Raman analysis is used for analysis of semiconductor nano structures.

8. Is Raman spectroscopy sensitive to temperature? and what is the resolution of the raman? Can it be used to map the chemicals' location? Raman spectra typically require resolution <1 nm, the line width is temperature sensitive. Raman spectral imaging can be used to locate chemicals. The excitation laser shifts.

9. How would you know if any chemical is pure or only some portion of pure chemical is mixed with impure chemical? Algorithms are designed such that analysis can be done assuming a pure chemical, and if no pure is found it can automatically look into mixtures.

10. What do I need to do in order to use the technology for inspecting some materials a mile away? Thanks Stand-off Raman spectroscopy is being investigating by attaching a telescope in front of the spectrometer typically a few hundreds of meters. I haven't seen any work done for a mile away.

11. I know THz isn't a subject area discussed in this talk, but from your experience, how do Raman scanners compare with THz scanners in the wealth and quality of spectral information when it comes to drug/explosive/substance quality control? I.e. spectral resolution, and success with matching a measurement to a spectral fingerprint found in a database. THz is not generally effective for bulk material analysis.

12. What should be typical laser spot size at sample for drugs/forensic to get reasonable signal strength? Conventional devices use spot sizes in the range of 50-150micron. Spot sizes in coded aperture designs are about a mm.

13. What is the smallest sample size for Raman spectroscopy? About the size of a rice grain, enough to cover the laser spot size. Raman microspectroscopy can look into even smaller samples.


1. What is compression Raman? Compressive sampling is estimation of more signal components than the number of measurements. Raman spectra typically consist of a sparse sharp features and thus are particularly amenable to compressive imaging techniques using multiplex spatio-spectral encoding.

2. Why Raman spectrometers do not interfere with water or glass? Because the excitation source is not absorbed and the Raman cross section is small in water and glass.

3. In reference to your comment that at UV the Raman signal could be 16 times more powerful. UV Raman will only make sense if you have UV source that is at most 1/16 times less bright than what you have at NIR. Ok. UV also has advantages for reduced fluorescence in the Raman regime in some cases.

4. What brightness levels are you getting with UV sources that you have? 15 mw.

5. What would be your ideal 210 nm source (pulsed, CW?) If pulsed, what pulse width? Quasi CW or mode locked OK? Narrow line width is desirable, so normally CW operation.

6. At 200 MW will sample heating affect Raman signature? Sample degradation from photo bleaching or other effects is more significant that heating.

7. What is a typical measurement time for a single point? 1-30 seconds

8. What is the reconstruction time for reconstructing the hyperspectral cube? How long does the computation take? On a GPU <1 seccond per frame, even 30 fps is possible.

9. Is there the chance to measure Raman signals in real time? If real time means 30 frames per second, then the combination of moderate laser power and high collection optics could allow this.

10. What is the size of the optics used for collecting the Raman Scatter? Can range from fiber interfaces to telescopes depending on signal levels and standoff.

11. Is Raman usable for minerals classification in food and drinks (e.g. Ca in milk)? Sure, see G.P.S. Smith, K.C. Gordon, S.E. Holroyd, Raman spectroscopic quantification of calcium carbonate in spiked milk powder samples, Vibrational Spectroscopy, Volume 67, July 2013, Pages 87-91, ISSN 0924-2031,

12. What is the smallest Raman shift that can be detected? Interesting question, the answer depends on how bad one wants to know. Ultimately the measurable shift is limited by the excitation laser line width.

13. Do you use CW or pulsed laser in coded aperture? CW


1. Future prospect of Raman analysis in Medical diagnosis...? Standard Raman is close to feasibility for blood glucose and blood alcohol measurement. System cost and algorithm development are central challenges. Raman using prepared surfaces for metabolic analysis of blood or tissue and for pathogen detection is violable now.

2. Is Raman spectroscopy applicable for industry when it takes seconds or minutes to measure one single Raman signal? Sure
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