Abstract

An integrated fiber-optic sensor is described that uses incoherent broadband cavity enhanced absorption spectroscopy for sensitive detection of aqueous samples in nanoliter volumes. Absorption was measured in a 100 µm gap between the ends of two short segments of multimode graded-index fiber that were integrated into a capillary using a precision machined V-grooved fixture that allowed for passive fiber alignment. The other ends of the fibers were coated with dielectric mirrors to form a 9.5 cm optical resonator. Light from a fiber-coupled superluminescent diode was directly coupled into one end of the cavity, and transmission was measured using a fiber-coupled silicon photodiode. Dilute aqueous solutions of near infrared dye were used to determine the minimum detectable absorption change of $2.4\times {10}^{-4}$ under experimental conditions in which pressure fluctuations limited performance. We also determined that the absolute minimum detectable absorption change would be $1.6\times {10}^{-5}$ for conditions of constant pressure in which absorption measurement is limited by electronic and optical noise. Tolerance requirements for alignment are also presented.

©2012 Optical Society of America

Incoherent broadband cavity enhanced absorption spectroscopy using supercontinuum and superluminescent diode sources

Antti Aalto, Goëry Genty, Toni Laurila, and Juha Toivonen
Opt. Express 23(19) 25225-25234 (2015)

Incoherent broadband cavity-enhanced absorption spectroscopy for sensitive measurement of nutrients and microalgae

Haodong Zhang, Jing Luo, Saimei Hou, Zhanpeng Xu, Julian Evans, and Sailing He
Appl. Opt. 61(12) 3400-3408 (2022)

Real-time trace gas sensor using a multimode diode laser and multiple-line integrated cavity enhanced absorption spectroscopy

Andreas Karpf and Gottipaty N. Rao
Appl. Opt. 54(19) 6085-6092 (2015)

High-resolution Fourier-transform cavity-enhanced absorption spectroscopy in the near-infrared using an incoherent broad-band light source

Johannes Orphal and Albert A. Ruth
Opt. Express 16(23) 19232-19243 (2008)

Ultrasensitive near-infrared integrated cavity output spectroscopy technique for detection of CO at 1.57 μm: new sensitivity limits for absorption measurements in passive optical cavities

Gregory S. Engel, Walter S. Drisdell, Frank N. Keutsch, Elisabeth J. Moyer, and James G. Anderson
Appl. Opt. 45(36) 9221-9229 (2006)