ABSTRACT
Real-time detection of the concentration of input fluid is essential for optofluidic sensing, especially in the case of biochips and organ-on-a-chip systems. In this paper, a microcantilever structure that enables temperature and liquid concentration sensing was fabricated on the tip of the optical fiber by femtosecond laser direct writing (two-photon polymerization, TPP) technology. An open Fabry-Pérot interferometer (F-P) structure was formed between the end of the optical fiber and the cantilever, so the sensor becomes quite sensitive to the localized temperature, concentration and refractive index of the target liquids. The reasonable size parameters of the cantilever were determined by structural stress analysis and interference spectrum analysis. By integrating the fiber sensor with a microfluidic chip, an on-chip optofluidic sensing platform is developed, which shows high sensitivities of the temperature (92.7 pm °C-1), concentration (0.3287 nm (g L-1)-1), and refractive index (1385.819 nm RIU-1). The reported optofluidic sensing platform demonstrates reasonably high stability and satisfactory sensing effect, holding great promise for applications in lab-on-a-chip systems.
Subject(s)
Lasers , Optical Fibers , Equipment Design , RefractometryABSTRACT
An ultracompact fiber router based on a photo-controlled microbubble was proposed in this Letter. Because the microbubble can be repositioned precisely in the fiber microcavity by adjusting the drive laser power, the target light beam that was incident on the gas-liquid interface of the microbubble was routed toward different directions by the light refraction inside the photo-controlled microbubble. Experimental results showed that the device had a low insertion loss of 0.64 dB, response time of (1.2-1.8s), and can achieve the continuous beam redirections within an angle range of 56° by exploiting a drive laser power of only 1.8 mW. With the characteristics of excellent controllability, low consumption, and no electromechanical parts, such a fiber all-optical router has potential to be used for the multiplex treatments and analysis applications of the photonic laboratory on a chip (PLOC).
ABSTRACT
We experimentally demonstrated a novel photocontrol scheme of a microbubble. The microbubble was confined in a fiber-based hollow microstructure and its movement was driven by the laser-induced photothermal Marangoni force. The position of the microbubble was controlled at a micrometer scale by simply adjusting the drive laser power. This scheme permitted the firsthand control of a microbubble with a divergent single laser beam. As a practical demonstration, we proposed a variable fiber all-optical attenuator by exploiting the total internal reflection on the surface of the photo-controlled microbubble to modulate the target light beam. The experimental results showed that such a compact fiber attenuator possessed a low insertion loss of 0.83 dB, a maximum extinction ratio of 28.7 dB, and had potential to be integrated into the lab-on-a-chip for the modulation of the light beam power.
ABSTRACT
A simple fiber-optic sensor for simultaneous measurement of high pressure and high temperature was proposed. The sensor was simply fabricated by splicing two sections of silica capillary tubes (SCTs) with different inner diameters to the single-mode fiber. The thick core SCT functions as a Fabry-Perot (FP) micro-cavity and an anti-resonant reflecting waveguide at the same time. The two different sensing mechanisms lead to the high contrast sensitivity values of pressure and temperature (â3.76 nm/MPa, 27.7 pm/°C and 4.24 nm/MPa, 0.82 pm/°C). We also proposed a simple and effective method to evaluate the actual sensitivities of two-parameter sensors by using linear programming, which shows that our sensor is more sensitive than others in high pressure and high temperature simultaneous detection. Besides, low cost, good mechanical property and convenient reflective probe make the sensor more competitive in actual application.
ABSTRACT
An optical fiber strain sensor based on capillary-taper compensation structure was proposed. The theoretical simulation by using the finite element analysis method shows a matching condition between the capillary length and the interference-cavity length to achieve the zero temperature crosstalk. Meanwhile, the strain sensitivity can also be improved greatly at the matching condition. We then set up an insertion controller system with high accuracy to make sure the interference-cavity length can match the capillary length. Finally the fiber strain sensor with both ultra-low temperature-crosstalk (0.05 pm/°C) and ultra-high sensitivity (214.35 pm/µÎµ) was achieved, and the experimental results agreed well with the calculated results. The "ladder-mode" and repeatability experiments showed that the proposed sensor was actually with the ultra-low detection limit of 0.047 µÉ.
ABSTRACT
A strain force sensor based on fiber inline Fabry-Perot (FP) micro-cavity plugged by cantilever taper was proposed. The structure was fabricated by simple and cost-effective method only including fiber cleaving, tapering and splicing. The active-length of the FP micro-cavity reached 1360 µm, while the interference length was only 3.5 µm. Owing to the ultra-long active-length and ultra-short interference length, the strain force sensitivity of the fiber inline FP micro-cavity plugged by cantilever taper reached as high as 841.59 nm/N. Besides, the proposed structure showed good linearity (99.9%) in the sensing process and small temperature crosstalk (11 pm/ ÌC). It can be used as a practical and reliable strain force sensor.
