Free-Form Optics Enhanced Confocal Raman Spectroscopy for Optofluidic Lab-on-Chips

• Published in: IEEE journal of selected topics in quantum electronics Vol. 21; no. 4; pp. 79 - 86
• Main Authors: De Coster, Diane, Loterie, Damien, Ottevaere, Heidi, Vervaeke, Michael, Van Erps, Jurgen, Missinne, Jeroen, Thienpont, Hugo
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.07.2015; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Computer simulation; Confocal; confocal detection; Devices; Ethyl alcohol; Laser beams; Laser excitation; Lenses; Optical scattering; optics; Pollution measurement; polymer; Polymethyl methacrylate; Polymethyl methacrylates; Raman scattering; Raman spectroscopy; rapid prototyping; Semiconductor device measurement; Spectrometers; Spectrum analysis; polymer; confocal detection; Raman spectroscopy; optics; rapid prototyping
• ISSN: 1077-260X; 1558-4542
• DOI: 10.1109/JSTQE.2014.2381470

We present an optofluidic lab-on-chip for confocal Raman spectroscopy, which can be used for the analysis of substances. The device strongly suppresses unwanted background signals because it enables confocal detection of Raman scattering thanks to a free-form reflector embedded in the optofluidic chip. We design the system using non-sequential ray-tracing combined with a mathematical code to simulate the Raman scattering behavior of the substance under test. We prototype the device in polymethyl methacrylateby means of ultraprecision diamond tooling. In a proof-of-concept demonstration, we first show the confocal behavior of our Raman lab-on-chip system by measuring the Raman spectrum of ethanol. In a next step, we compare Raman spectra measured in our lab-on-chip with spectra measured with a commercial Raman spectrometer. Finally, to calibrate the system we perform Raman measurements on urea solutions with different concentrations with our proposed experimental proof-of-concept setup. We achieved a detection limit that corresponds to the noise equivalent concentration of 20 mM.