A novel temperature sensor by using photonic bandgap (PBG) effect is demonstrated. The solid core photonic bandgap
fiber (PBGF) with infiltrated high refractive index solution is used for temperature measurement. Two high index
solutions were infiltrated with refractive index of 1.58 and 1.64. It shows that the rising photonic bandgap edges of
PBGF have a blue shifting. The 112.40nm shifting was observed with 1.58 refractive index oil infiltrated when the
ambient temperature was changing from 24°C to about 65°C. The better sensitivity of the temperature measurement
2.74nm/°C was achieved.
Sol-gel entrapment technique is proposed for glucose oxidase immobilization in long period grating glucose sensor. The
glucose oxidase is encapsulated in transparent sol-gel matrix to detect the presence of D-glucose molecules. A sensitivity
of 39.8mM/nm was achieved for the fabricated glucose biosensors.
In order to achieve photonic band-gap effect as sensing mechanism and improve biocompatibility of relatively lower-cost
silica-core phonic crystal fibers (SCPCF) and make use of photonic band-gap effect as sensing mechanism, polymer
with similar biocompatibility as PMMA coating in SCPCF air-holes is proposed in this paper. In order to evaluate the
polymer coating effect, a three-layer model of air hole is proposed. The wavelength shifts of photonic band-gap edges
(PBEs) were evaluated by plane wave expansion (PWE) method, assuming refractive index of silica n<sub>s</sub>, polymer n<sub>p</sub> and
air n<sub>a</sub> are 1.45, 1.50 and 1.00 respectively. Blue shifting of bands are observed in the simulation and the bandwidth of
each band-gap becomes narrower with the increasing of air ratio. The result shows that 1nm change of air hole is able to
obtain a wavelength shift of 0.43nm. Assuming the wavelength shift of 0.01nm can be detected, a small air hole variation
of 0.023nm can be measured.
Hollow-core photonic bandgap fiber (HC-PBGF)–based evanescent wave biosensors are demonstrated and analyzed theoretically and experimentally. With 95% of the guided light power residing in the samples, the measured absorbance for a 30-cm-long fiber filled with a 0.2 µM Alexa Fluor 700–labeled DNA Oligo solution is 1.06. This is in good agreement with the theoretical prediction, which is evaluated by using the refractive index scaling law. The HC-PBGFs thus offer both efficiency and simplicity for the detection of biomolecules in ultra-small sample volumes.
Refractometric sensor utilizing spectral properties of antiresonant guiding photonic crystal fibers is proposed. The sensor
operation is based on the wavelength shift of the transmission spectrum with respect to the change of refractive index
inside the air holes of the photonic crystal fibers. Both numerical and experimental analyses are carried out to investigate
the spectral characteristics.
A novel concept of cavity ring-up (CRU) spectroscopy is proposed for trace gas detection in an amplified fiber loop.
Based on a rate equation approach, the time-evolving CRU signals in the fiber gas sensing loop are studied. The features
of CRU output signals are numerically simulated and discussed. Those systemical studies and theoretical analyses will
guide the future design of the fiber cavity ring-up gas sensing system.
A hybrid guiding liquid-crystal photonic crystal fiber is proposed, in which two polarization components (E<sub><i>x</i></sub> and E<sub><i>y</i></sub>) are
confined by modified total internal reflection and bandgap guidance, respectively. With the aid of scalar wave
approximation, the distinct features in band structures of liquid-crystal photonic bandgap fibers are successfully
identified. This hybrid guiding feature makes it possible to achieve single-polarization single-mode guiding and high
birefringence guiding effect in different wavelength ranges. Particularly, high birefringence in an order of 10<sup>-2</sup> can be
The use of photonic bandgap fibers (PBGF) for biomedical sensing has been demonstrated. The demonstrated PBGF has a blue wavelength shift of 280 nm in the falling photonic bandgap edge (PBE) when the ambient refractive indices inside the holey region change from 1.333 to 1.39, which agrees well with the analytical prediction. Combining this with the knowledge of immobilization techniques and biorecognition elements could open up a new class of PBGF-based label-free biosensors. A sensitivity on the order of 0.1 nmol/L could be achieved by consuming less than 1 µL of sample.
An optical waveguide for measuring the change of refractive index (RI) by using a photonic crystal fiber is designed. The simulation results show that a variation of 3.5% refractive index unit (RIU) could shift the resonant wavelengths of 450 and 110 nm when the RIs of liquid are 1.5 and 1.7, respectively. The sensitivities of 8×10?7 and 3.2×10?6 RIU are thus able to be achieved for the RIs of liquid of 1.5 and 1.7, respectively.
The transmission spectrum of a photonic bandgap fiber filled with low index material is investigated. A simple analytical model is developed to predict the position and bandwidth of the band gap in the wavelength domain with respect to the refractive index. The wavelength of the band gap has a blue shift and the bandwidth of the band gap becomes narrow with the increasing of the refractive index of the filled material. The degree of shifting of the band gap increases with the reduction of air-filling fraction of the photonic bandgap fiber.
An optical waveguide for measuring the change of refractive index by using a photonic crystal fiber is designed. The simulation results show that a variation of 0.032 refractive index unit (RIU) could shift the resonant wavelengths of 245nm and 68nm when the refractive indices of liquid are 1.5 and 1.7, respectively. The sensitivity for the refractive index measurement of about 1.3×10<sup>-6</sup>RIU is achieved.
A general analysis of an inserted LPG in air-clad PCF for temperature and strain measurement is presented. The temperature and strain can be detected simultaneously by matrix inversion. The maximum temperature errors are 3<sup>o</sup>C and 0.8<sup>o</sup>C in the temperature ranges from 35<sup>o</sup>C to 50<sup>o</sup>C and 90<sup>o</sup>C to 120oC, respectively. The corresponding maximum strain errors are 250με and 135με in the strain range from 0 to 3000με respectively.
We report a novel clinometer (or tilt sensor) by using three fiber Bragg gratings (FBGs). It can detect the magnitude as well as the direction of the inclination from the horizontal direction by directly measuring the reflected optical powers of the FBGs, whose bandwidths vary with the inclination. The experimental results show that it is inherently insensitive to temperature, eliminating the need for compensation of temperature, and a tilt angle measurement accuracy of ±0.13° and resolution of 0.02° have been achieved.