Liquid mixture detection by InGaAsP semiconductor lasers

Xiang Zhu; Daniel T. Cassidy

doi:10.1117/12.263486

10 January 1997 Liquid mixture detection by InGaAsP semiconductor lasers

Xiang Zhu, Daniel T. Cassidy

Proceedings Volume 3000, Laser Diode and LED Applications III; (1997) https://doi.org/10.1117/12.263486
Event: Photonics West '97, 1997, San Jose, CA, United States

Abstract

Compact liquid sensors were constructed by using the output of near-infrared semiconductor diode lasers to measure transmission. Multiple short external cavities were used to force diode lasers to provide a wide spectral coverage (approximately equals 72 nm) for the detection of broad absorption features of liquids. The transmission at discrete laser modes were processed by the principal component regression (PCR) and the partial least squares (PLS) algorithms. A root mean square error of prediction of 0.092% and a correlation coefficient R² of 0.998 were obtained for the detection of water concentration in D₂O. The rms value of 0.056% from 30 independent measurements of 0.5% water in D₂P showed that the method was sensitive to detect 0.1% concentration difference. The application of the PCR and the PLS algorithms in the scheme was studied in a three mixture system of water, acetone and methanol in terms of optimizing factors and detection of 'outliers'. The limiting noise sources were determined by modeling synthetic data.

Citation Download Citation

Xiang Zhu and Daniel T. Cassidy "Liquid mixture detection by InGaAsP semiconductor lasers", Proc. SPIE 3000, Laser Diode and LED Applications III, (10 January 1997); https://doi.org/10.1117/12.263486

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