Subwavelength film sensing based on terahertz anti-resonant reflecting hollow waveguides

• Published in: Optics express Vol. 18; no. 18; pp. 19353 - 19360
• Main Authors: You, Borwen, Lu, Ja-Yu, Liou, Jia-Hong, Yu, Chin-Ping, Chen, Hao-Zai, Liu, Tze-An, Peng, Jin-Long
• Format: Journal Article
• Language: English
• Published: United States 30.08.2010
• Subjects: Acrylic Resins; Algorithms; Anisotropy; Biosensing Techniques; Fiber Optic Technology; Interferometry - methods; Models, Statistical; Optical Fibers; Optics and Photonics; Polypropylenes - chemistry; Polyvinyls - chemistry; Reproducibility of Results; Terahertz Spectroscopy - methods; Time Factors
• ISSN: 1094-4087; 1094-4087
• DOI: 10.1364/OE.18.019353

A simple dielectric hollow-tube has been experimentally demonstrated at terahertz range for bio-molecular layer sensing based on the anti-resonant reflecting wave-guidance mechanism. We experimentally study the dependence of thin-film detection sensitivity on the optical geometrical parameters of tubes, different thicknesses and tube wall refractive indices, and on different resonant frequencies. A polypropylene hollow-tube with optimized sensitivity of 0.003 mm/μm is used to sense a subwavelength-thick (λ/225) carboxypolymethylene molecular overlayer on the tube's inner surface, and the minimum detectable quantity of molecules could be down to 1.22 picomole/mm(2). A double-layered Fabry-Pérot model is proposed for calculating the overlayer thicknesses, which agrees well with the experimental results.