By now, it is still extremely challenging to accurately measure femto-Newton (10-15 N) optical forces. Here, a simple scheme of a suspended tapered nanofiber coupled with a glass substrate is demonstrated to generate and sense the fN optical force, where the ~10 nm deformation of the nanofiber can be resolved by white light interferometry and an ultra-low stiffness of 0.540 fN/nm is obtained for the suspended nanofiber through Brownian motion. Owing to the ultra-low stiffness of the nanofiber, the scheme provides a cost-effective method to sense and measure ultra-weak (5.2 fN) optical force. Moreover, the scheme also provides a simple way to exploit fN optical forces for implementation of micro-Watt all-optical devices.
A high resolution fiber optic spectrometer system was set up, which consists of a tunable laser, a fiber optic power meter, GPIB-USB data acquisition cards, and a computer control platform. The wavelength absolute accuracy of the tunable laser (Santec TSL-550) is±2.5pm, and the wavelength setting resolution can be 0.1pm, which makes the system features high resolution. However, the resolution of the laboratory fiber optic spectrometer (YOKOGAWA AQ6317C) can only be set to 20pm. The extinction ratio (ER), free spectral range (FSR) and the trough position of the spectrum of the microfiber knot resonator (MKR) is measured with our system and AQ6317C fiber optic spectrometer. The experimental results of the two methods show that the ER and FSR are offset by 0.675dB and 0.003nm, respectively, and the standard deviations are 0.17% and 0.43%, respectively. From the results, and the stability of MKR is considered, we conclude that the resolution of our system can be better than 1nm due to the resolution of the TSL-550 light source, and the overall standard deviation is also smaller, therefore, the repeatability and stability of our testing system are better than the AQ6317C fiber optic spectrometer, which can better meet the actual measurement requirements.
In this paper, the feasibility of multimode fiber as pressure sensor is explore by using the straight structure of the fiber itself. The elastic mechanical model and the basic equation of the straight structure of the fiber is established. ANSYS software is used for the analysis of stress and strain distribution and the results show that the stress and strain of load section fiber are linearly related. In the experimental process, the straight structure fiber is used as the test unit and the change of the optical power is measured and analyzed during the pressure loading. The experimental results show that the linear correlation coefficient R2 of the pressure loading process from 0g to 400g is 0.9117 for the multi-mode fiber; and the linear correlation coefficient R2 of the pressure unloading process from 400g to 0g is 0.7061. So it can be concluded that the straight structure multimode fiber can be used as a pressure sensor.
Optical fibers have long been the backbone of modern communication system. One way of extending the capability of optical fibers is to thin down the core sizes as microfiber which facilitates light-matter interaction through evanescent light. Among different microfiber based structure, the microfiber knot resonator (MKR) is a resonant structure which finds applications in lasing, filtering and optical switching [1-2]. Particularly, when the MKR structure is combined with functional two-dimensional materials, a large panel of devices can be achieved via the investigation of variations in resonance properties.
Here, a layered metal dichalcogenide semiconductor tin disulfide (SnS2), characterized with high intrinsic electron mobility and strong absorption in the visible light regime [3], is chosen to be coated onto MKR. The all-optical control of light functionality is demonstrated in MKR with SnS2 structure where the signal light power is controlled by the external violet pump power via the absorption property of SnS2. The device fabrication, characterization and obtained experimental results will be presented in the talk.
We propose the electro-optic mode deflection devices based on annealed proton exchange (APE) waveguides in lithium niobate with microstructured electrodes. Two mode deflection devices with right-triangle-shaped electrodes (Device A) and isosceles-triangle-shaped electrodes (Device B) are investigated. Taking advantage of the refractive index prism array formed when applying an external voltage to the electrodes, the mode can be deflected. Beam smoothing can be achieved by applying alternating voltages. A∼1.28 μm beam deflection is obtained by applying a voltage (20 V) for Device A. For Device B, a 3.52 μm beam deflection is obtained by applying a -15 V voltage to the electrodes. Device B has a horn-shaped input waveguide which ensures that the output is a quasi-single mode. The mode quality of the deflection beam is also quantified by the CMOS camera. Smoothing the non-uniform density distribution of light beam is confirmed by averaging over 69 images taken by the CMOS camera with alternating voltage. These electro-optic mode deflection devices have potential applications in electro-optic sampling, high-speed optical switch, and beam smoothing of a high-power laser.
Light control-light characteristics of a micro fiber (MF) coated with tungsten disulfide (WS2) nanosheets is demonstrated in this paper. A device with WS2-coated MF has been fabricated, and the transmitted optical powers of the device are measured with 405 and 660 nm pump lasers. By tuning the pump lasers, we achieve the all light controllable sensing of WS2-coated MF over a broadband wavelength range from 1520 to 1620 nm, offering competitive sensities of 0.238 and 0.136 dB/mW for 405 and 660 nm pump lasers, respectively. In addition, The rise and fall times of the transient response to pump lasers are also measured. For the 405 nm laser, the rise and fall times of the transient response are 0.32s and 0.42s, respectively. For 660 nm laser, the response times toward the presence (removal) of the pump light transient response are 0.28s and 0.37s, respectively. Experimental results indicate that the device integrated with WS2 could hold promising potentials in photoelectric and photonic applications.
We demonstrated strain sensing of a microfiber with a microarched transition region, which was fabricated by flame heated tapering. Due to multimode interference of different propagation modes of microfiber, two main transmission dips were observed at 1215.0 and 1469.8 nm. Enhanced by the microarched transition region, the depth of the dip was up to 19 dB at 1215.0 nm. The position of the dip red-shifted while the axial strain changed from 0 to 1166.2 μϵ. The axial strain sensitivity was up to 56.6 pm/μϵ, which was one order of magnitude higher than that of the traditional optical strain sensor based on microfiber or fiber Bragg grating. The linear correlation coefficient was 98.21%. This kind of microfiber with a microarched transition region can be widely used in various physical, chemical, and biological sensing and detection fields.
In this paper, we report a new filter by combining fiber-optic microring and lithium niobate microwaveguide chip. In our design, fiber-optic microring works as a resonator to trapped the resonant light and enlarge its optical energy. The lithium niobate microwaveguide chip serves as a mount to load the fiber-optic microring on the microwaveguide. Then the resonant light coupled from the microring could transmit through the microwaveguide and be detected. We experimentally demonstrated our design and its operation feasibility. The characteristic of the filter could be clearly observed. The results proved that the combination of fiber-optic microring and lithium niobate microwaveguide chip might provide an alternative way to integrate the fiber-optic micro and nanodevices on lithium niobate microwaveguide chip.
We demonstrated temperature sensing of a side-polished fiber with polymer nanoporous film cladding, which was constructed by dehydrating dichromate gelatin film on the polished surface. Due to intermodal interference of core mode and cladding mode, two main transmission valleys were observed at 1219.2 and 1373.2 nm. The modulation amplitudes are ∼8 and 12 dB, respectively. These two transmission valleys show significant sensitivity to the temperature. At the wavelength of 1373.2 nm, the position of transmission valley blueshifted 114 nm while the temperature changes from 30°C to 90°C, and the sensitivity of temperature was up to 1.92 nm/°C. The linear correlation coefficient was 98.67%. The temperature sensing characteristics of nanoporous cladding fiber was successfully demonstrated, and it shows a high potential in photonics applications.
We established a theoretical model for a single knot-ring resonator and investigated the transmission spectrum by Jones matrix. The numerical results show that two orthogonal polarization modes of knot-ring, which are originally resonated at the same wavelength, will split into two resonant modes with different wavelengths. The mode splitting is due to the coupling between the two orthogonal polarization modes in the knot-ring when the twisted angle of the twist coupler is not exactly equal to 2mπ (m is an integer). It is also found that the separation of the mode splitting is linearly proportional to the deviation angle δθ with a high correlation coefficient of 99.6% and a slope of 3.17 nm/rad. Furthermore, a transparency phenomenon analogous to coupled-resonator-induced transparency was also predicted by the model. These findings may have potential applications in lasers and sensors.
A novel type of coreless side-polished fiber (CSPF) was investigated numerically and experimentally for sensing refractive index (RI). Numerical simulations and experiments found that multi-mode interference can be excited at the transitional section of coreless side-polished fiber, leading to resonant dips in transmission spectrum through such a CSPF. A red shift of such dips was observed due to increase in surrounding RI, whereby the CSPF can be used as RI sensor. Interestingly, by such a simple CSPF structure, ultra-high sensitivity of 7225nm/RIU for RI range of 1.432 to 1.434 was achieved in our experiment. As the CSPF can act as a versatile platform, the high sensitivity of the CSPF will open new opportunities for other high sensitive sensors and fiber devices.
Because of high surface-to-volume ratio, few layers MoS2 material as a kind of 2D materials has been attracted more attention nowadays to be used for photonics devices. We investigated the performance of few-layer MoS2 when it is covered on a side polished fiber (SPF) to sense relative humidity (RH) of environments. The SPF was made by wheel side polishing method. The few layers MoS2 was deposited on the side polished surface to be a sensing material. As the environmental humidity changes, the output optical power of the all fiber sensor will change due to the interaction between evanescent field of fiber and MoS2 material. The change of output power of fiber sensor can reach 16.67dB in the relative humidity range of 40-85%. Experiments using the fiber sensor on human breathing have been made and the respondence has achieved. The experiments showed that the fiber sensor can be used in medical instruments. Key words: fiber sensor, side-polished fiber, humidity sensing, 2D material, MoS2.
This study reports on the development and testing of a cost- and time-effective means to optimize a double-sided hemispherical patterned sapphire substrate (PSS) for highly efficient flip-chip GaN-based light-emitting diodes (LEDs). A simulation is conducted to study how light extraction efficiency (LEE) changed as a function of alteration in the parameters of the unit hemisphere for LEDs that are fabricated on a hemispherical PSS. Results show that the LEE of LED flip chip could be enhanced with the optimized hemispherical PSS by over 0.508 and is ∼115.3% higher than that of flip-chip LEDs with non-PSS. This study confirms the high efficiency and excellent capability of the optimized hemispherical PSS pattern to improve LED efficacy.
The organic acetone vapor sensing characteristics of side-polished fiber coating with cholesteric liquid crystal film were investigated. The cholesteric liquid crystal used in our experiments is a mixture compound, which contains 30% cholesteryl oleyl carbonate, 60% cholesteryl pelargonat, and 25% cholesteryl chloride. When cholesteric liquid crystal film was coated on the surface of side-polished fiber, an interference transmission spectrum of fiber could be observed. When the fiber is exposing in acetone vapor, a blue shift of the interference spectrum was found. The higher concentration of acetone vapor is, the larger blue shift of spectrum is found. The shift of transmission spectrum is linear to the concentration of acetone vapor. The sensitivity is 1.356nm/vol% when the concentration of acetone vapor ranges from 3vol% to 16vol%. This study demonstrates a new all-fiber low-cost and portable acetone vapor sensor. It can be also used to investigate the helical structure and molecular orientation of cholesteric liquid crystal.
Sensing the nanometric displacement of a micro-/nano-fiber induced by optical forces is a key technology to study optical forces and optical momentum. When the gap between a micro-/nano-fiber and glass substrate becomes down to micrometer scale or less, a white light interference was observed. The gap changes when optical force arising from the propagating pump light along the micro-/nano-fiber causes a transversal nanometric displacement of a micro-/nanofiber, resulting in movement of the interferometric fringes. Therefore this movement of the interferometric fringes can be used to sense the nanometric displacement of the micro-/nano-fiber induced by optical forces. Experimental results show that the resolutions of this method can reach 7.27nm/pixel for tilted angle 0.8o between the micro-/nano-fiber and substrate. It is concluded that the white light interferometry method is suitable for measuring the weak optical force.
A temperature fiber sensor with nanostructured cladding composed ted by titanium dioxide (TiO2) nanoparticles was demonstrated. The nanoparticles self-assembled onto a side polished optical fiber (SPF). The enhancement of interaction between the propagating light and the TiO2 nanoparticles (TN) can be obtained via strong evanescent field of the SPF. The strong light–TN interaction gives rise to temperature sensing with a optical power variation of ~4dB in SPF experimentally for an environment temperature ranging from -7.8°C to 77.6°C. The novel temperature sensor shows a sensitivity of ~0.044 dB/°C. The TN-based fiber-optic temperature sensor is facile to manufactured, compatible with fiber-optic interconnections and high potential in photonics applications.
A novel all fiber-optic power sensor of violet laser based on methyl blue-functionalized reduced graphene oxide (MB-rGO) film coated on a microfiber (MF) was proposed. The experiments show that when the violet laser illuminating onto the MB-rGO film with power variation from 0.03mw to 12.8mw, the transmitted optical power of the MF changes with a relative variation of ~2.7dB. The novel power sensor of violet laser possesses a sensitivity of ~0.22dB/mw in 1550nm. Furthermore, the MB-rGO-based all fiber-optic violet power sensor is easy to fabricate, compatible with fiberoptic systems and possesses high potentiality in photonics applications such as all fiber-optic broadband sensors, switches and modulators.
We have investigated the influence of side-polished multimode fiber (SPMMF) core diameters D and residual radius R (the minimum distance between side-polished surface and the center of multimode fiber) on the sensitivity of a SPMMF based refractometer. We show that the residual radius has significant influence on the refractive index (RI) sensitivity but the core diameter does not. A refractometer with a lower SPMMF core diameter has a higher sensitivity. Experimental investigations achieved a maximum sensitivity of 42.23 dB/RIU (refractive index unit) for a refractive index range from 1.300 to 1.440 for a refractometer with a SPMMF core diameter of 50 μm.
A novel all fiber-optic temperature sensor based on graphene film coated on a side polished fiber (SPF) was
demonstrated. Significantly enhanced interaction between the propagating light and the graphene film can be achieved
via strong evanescent light of the SPF. The experiments shows that the strong interaction results in temperature sensing
with a dynamic optical power variation of 11.3dB in SPF. The novel temperature fiber sensor possesses a linear
correlation coefficient of 99.4%, a sensitivity of 0.13dB/°C, a precision of better than 0.03°C. Furthermore, the
graphene-based all fiber-optic temperature sensor is easy to fabricate, compatible with fiber-optic systems and possesses
high potentiality in photonics applications such as all fiber-optic temperature sensing network.
The orientation of nematic liquid crystal (NLC) can be used in biosensor. The sensing characteristics of side-polished fiber (SPF) for determination of azimuthal orientation of NLC have been investigated. The relationship between the azimuthal angle of NLC director and the optical transmission power in SPF was derived by empirical approach. Experimental results showed that the azimuthal transition of liquid crystal affected the optical transmission power in SPF. While the azimuthal angle increased from 0° to 90°, the optical transmission power increased by 28.10dB, which is similar to the variation tendency of the empirical analysis. When it changes from 0° to 30°, the azimuthal angle is linear to the change of optical transmission power. The respondence of azimuthal angle for optical sensing is averagely 0.359dB/°. Experiments indicate that SPF can be used in determination of the azimuzal transition of NLC. It would be used for a new fiber optical biosensor based on the SPF and NLC.
A novel light power sensor is demonstrated by using side polished fiber (SPF) overlaid with a photoresponsive
liquid crystal hybrid film. The mixture of 15%Azo, 20% ZLI811, and 65% nematic liquid crystal is overlaid on the flat
area of SPF to form a mixture film of ~30m thickness. The film is irradiated by light of wavelength of 405nm through a
phase mask with a period of ~528nm. An absorption peak in the transmission spectrum of 1520-1620nm of optical fiber
is observed. Experiment shows that the wavelength of absorption peak will shift toward shorter wavelength as the
irradiation power increases. The change of wavelength of absorption peak is approximately linear to the irradiation
power while the irradiation powers are between 30-80mw in our initial experiments. The measured sensitivity of light
power is about 1.154pm/uW for the demonstrated sensor.
Using a side polished standard fiber (SPF) as a sensor which is very sensitive to external refractive index, liquid crystal
hybrid film mixed with Azobenzene(AZO) and ZLI811 is overlay on the polished region of the SPF, and the
photorefractive effect of the film with UV light irradiation is studied. The mixture composed of liquid crystal, AZO, and
ZLI811 was coated on the polishing area after the SPF was calibrated. The optical power transmission of the SPF
changes when the photosensitive film on the SPF is under UV irradiation. Through curve of optical power transmission
which functions as refractive index, refractive index change of liquid crystal hybrid film is measured. Our experimental
result shows that the photosensitive thin film is a negative photosensitive material, and the refractive index changes from
1.474 to 1.470 under UV light irradiation. This photosensitive film material can be potentially used to create a new
all-fiber optical-controllable components and sensors.
Two kinds of optical fiber sensors that are fabricated with fiber side polishing technique are proposed and
demonstrated experimentally to measure the concentration of acetic acid solution. One kind is side polished fiber
Bragg grating (SPFBG) sensor, which is fabricated by side polishing the cladding over the grating region of fiber
Bragg grating. The reflective Bragg wavelength of SPFBG sensor shifts when its polished region is overlaid with
different concentration of acetic acid solution, so the concentration of acetic acid solution could be measured. Its
resolution is 6.67%. The other kind is side polished fiber (SPF) sensor fabricated by single mode fiber whose part of cladding is side polished. The concentration of acetic acid could be measured by the transmitted optical power when polished region is overlaid with acetic acid solution. Its resolution of sensor is 0.55%.
Using full-vector finite element method, transverse optical forces induced by strongly evanescent coupling between
two identical nanofibers is theoretically investigated. It shows that anti-symmetry and symmetry modes can induce
attractive and repulsive force, respectively. When light power of the symmetry (anti-symmetry) mode at 980nm
wavelength is 50mW, the gap between the nanofibers with 400nm diameter nears 392nm, the repulsive force reaches
maximum (11.5 pN/μm), which results in 30nm displacement at the center of 100μm-long free-standing nanofiber.
Based on pump-probe scheme, a novel potential method for optical force measurement is proposed. Using
Euler-Bernoulli beam equation and coupled mode theory for waveguides, the deformation impact on the splitting ratio of
coupling nanofibers is also investigated. It is found that, through the deformation, the repulsive force from 0.9 to 17
pN/μm can change the splitting ratio of coupling nanofibers from 0 to 600 when coupling length of nanofibers is fixed at
100μm, the gap is 400nm and probe light is at 808nm. It shows that measuring the splitting ratio of the strongly coupling
nanofibers can potentially provide a high sensitive method for measuring the optical force.
LCD and edge backlight light guide panel (LGP) are one of the main parts of handset or mobile phone et al. The design
of LGP is vital technique to the design of backlight module. The aim of this paper is to design a handset LGP with LED
as the light source. Three design qualifications are simulated and analyzed with ASAP software. The three qualifications
are rough surface, diffusion-dots and microstructure. The analysis result shows that the factor of diffusion-dots is the
most important ingredient. The surface brightness, the luminance distribution and the light efficiency of LGP are
determined by the density of diffusion dots. The total light loss is also affected by the factor of diffusion-dots to the LGP
whose diffusion dots are printed. A handset LGP is designed according to the research in the paper. The simulation result
is satisfying as good as the practical outcome. The paper is useful to increase the brightness and uniformity of handset
LCD.
Visible and Near infrared spectroscopy was applied for the fast determination of alanine
aminotransferase with whole blood. First, spectra of different thickness (0.5mm, 1mm, 2mm, 4mm
) were investigated to explore Optimal Optical Path for determination. The results show that the whole
blood sample with 0.5mm thickness is more suitable for spectral analysis. And then Near infrared
spectroscopy of 176 samples were collected. Multiplicative scatter correction and second-order
differential method have been used to spectral pretreatment. Stepwise multiple linear regression
method and partial least squares regression method have been employed to establish quantitative
detection model to predict content of alanine aminotransferase in whole blood. The alanine
aminotransferase measured presents best result in calibration and prediction by Near-Infrared
Spectroscopy with partial least squares regression calibration model, and the calibration correlation
coefficient, the standard error of calibration and the standard error of prediction are 0.98, 2.42 and
7.22 respectively.
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