Aiming at the problem of the low sensitivity of conventional optical fiber-based gas refractive index sensors, an ultrasensitive tapered optical fiber coupler-based gas refractive index sensor enhanced by the Vernier effect is proposed and demonstrated. The birefringence property of the tapered optical fiber coupler allows it to support two passes of interferences in two orthogonal polarized states, and the superposition of these two interferences forms the Vernier effect. Theoretical analysis and numerical calculations indicate that, for the fiber couplers working in the gas medium when the waist width is within the range of 1.2 to 2.0 μm, the group birefringence difference between the even mode and odd mode equals zero. Thus the sensitivity toward the ambient gas refractive index can be enhanced significantly. To demonstrate these theoretical results, a tapered fiber coupler with a width of 1.6 μm and a length of 16.5 mm was fabricated, and ultrahigh sensitivities up to 22015.4 and −22690.0 nm / RIU were experimentally achieved. The proposed sensor has the merits of being easy to fabricate, having compact structure, and being cost effective. It has significant application prospects in the petrochemical and biomedical detection fields.
You have requested a machine translation of selected content from our databases. This functionality is provided solely for your convenience and is in no way intended to replace human translation. Neither SPIE nor the owners and publishers of the content make, and they explicitly disclaim, any express or implied representations or warranties of any kind, including, without limitation, representations and warranties as to the functionality of the translation feature or the accuracy or completeness of the translations.
Translations are not retained in our system. Your use of this feature and the translations is subject to all use restrictions contained in the Terms and Conditions of Use of the SPIE website.