Micro/nanofiber optical sensors

Abstract

As a low-dimensional optical fiber with diameter close to or below the wavelength of light, optical micro/nanofiber (MNF) offers a number of favorable properties for optical sensing, which have been exploited in a variety of sensing applications, including physical, chemical, and biological sensors. In this paper we review the principles and applications of silica, glass, and polymer optical micro/nanofibers for physical and chemical sensing.

Optical microfibers and nanofibers

“…Evanescent coupling between two adjacent MNFs is of special importance for designing nano fiber-optic devices such as couplers [13], modulators [95], resonators [81,96,97], lasers [34,[52][53][54]56], and sensors [22,28,31] which involve the near-field coupling process (e.g., direct interconnection with external optical systems through fiber tapers, energy exchange between two MNFs, or recirculation of optical energy inside ring resonators). Usually, evanescent coupling between adjacent weakly guiding waveguides (low-index-contrast waveguides) with a certain space (e.g., a few hundred nanometers) can be described by the perturbation theory [98].…”

“…(2) Strong evanescent field Strong evanescent field offers strong near-field interaction between the MNF and its surroundings, making the MNF highly favorable for optical sensing [21][22][23][24][25][26][27][28][29][30][31][32] and evanescent coupling between the MNF and other waveguides (e.g., a semiconductor [33,34], metal [35,36] nanowire or planar waveguide [37]) or a substrate [30,35,38,39]. Based on the high-efficiency evanescent coupling, a variety of optical components or devices (e.g., loop and knots resonators [40][41][42][43][44][45][46][47][48][49][50][51], lasers [52][53][54][55][56][57][58], and sensors [21][22][23][24][25][26][27]…”

“…Based on the high-efficiency evanescent coupling, a variety of optical components or devices (e.g., loop and knots resonators [40][41][42][43][44][45][46][47][48][49][50][51], lasers [52][53][54][55][56][57][58], and sensors [21][22][23][24][25][26][27][28][29][30][31][32]) have been demonstrated. Meanwhile, since the high fractional evanescent filed is tightly confined around the MNF, it can produce steep field gradient which provides large optical gradient force for manipulating cold atoms [19,[59][60][61][62][63] or micro-/nano-particles [64,65], as well as large or manageable waveguide dispersion under single mode condition [11].…”

Advances in optical fiber Bragg grating sensor technologies

“…Since the report of subwavelength-diameter silica wires for the low-loss optical wave guiding by L. M. Tong et al [47], microfibers with a diameter of about several microns have become a topic of intense research interests due to the strong evanescent wave and high-intensity surface field [48]. Such a microfiber is particularly suitable for ultrasensitive sensing applications [49][50][51][52][53].…”

Influence of a thin metal layer on a beam propagation in a biconical optical fibre taper

“…The basic element, which is a bi− conical optical fibre taper, allows controlling light beam propagation in the structure. This element is a base for man− ufacturing advanced hybrid elements like polarization con− trollers [5], optical switchers [6], white lasers [7] or optical sensors [8,9]. Finally, the tapering technology is relatively easy and cheap.…”