In this work, we thoroughly evaluate different types of lateral-offset Mach-Zehnder interferometers (MZIs) to search for the optimized design. Three different structures (SNS, SMNMS, and SNNNS. S: single-mode fiber; N: no-core fiber; M: multi-mode fiber) are proposed and their performances are compared numerically. Besides, for the SNNNS sensor, the effect of different no-core fiber (NCF) diameters on the sensor performance is discussed. The numerical analyses demonstrate that the SNNNS sensor with NCF diameter of 61.5 mu m shows the best performance among all the sensors. The experimental results confirm that, when compared with the SNS sensor, the SNNNS sensor is insensitive to the lateral-offset distance. It ensures an excellent interference performance within a large offset range, which facilitates the sensor fabrication. The optimized design of the sensor device shows the potential integration applications in the ultra-low concentration biomolecule detection field.

In this paper, we propose a four-wave mixing-based photonic crystal fiber (PCF) microfluid sensor, and two U-shape microslits fabricated by a femtosecond laser are embedded into the sensor for real-time microfluid measurement. Theoretical and experimental results prove that the signal wavelength is sensitive to both the refractive index (RI) and the material dispersion property of the liquid sample filled into the air channels. For different aqueous target samples at low concentrations, the responses of signal wavelength are consistent with each other. The obtained RI sensitivity is approximately 881.36 nm/RIU, and the sensing resolution is around 1.6 × 10-4 RIU. The proposed sensor also shows a better figure of merit (FOM) as high as 313.65 RIU-1 when compared with the fiber SPR sensors. Besides, the signal wavelengths present different responses with the increasing aqueous concentration due to the separated dispersion characteristics of the filled liquid samples, which can be potentially applied for the discrimination of liquid samples with a well-designed wavelength-coded sensor array in the future.

In this paper, a fiber SERS-DNA probe was fabricated with femtosecond laser ablation and laser-induced silver particle deposition, and a single DNA strand with a stem-ring molecular beacon was modified onto the probe. Deafness gene was detected in the target solution by monitoring the SERS signal intensity of the molecular beacon. The experimental results showed that low DNA concentration down to 10-10 M could be successfully detected with such a fiber SERS-DNA probe, which shows an alternative method for the detection of virulence gene.

In this paper, a compact temperature sensor was constructed based on controllable four-wave mixing (FWM) achieved by a partially filled solid-core photonic crystal fiber (PCF). With the help of a hollow-core fiber, the air holes of the PCF were partially filled with one layer, two layers, and four holes, respectively, thereby realizing a controllable output of signal wave. The response to temperature was tested and analyzed in the experiment. A sensitivity of 0.61 nm/°C was obtained from the room temperature to 150 °C with a fiber shortened to 25.8 mm. Both experimental and theoretical results showed that the response to the temperature could be with great linearity for the one-layer filled PCF, and the sensitivity of FWM-based sensor was almost unchanged when the sensing fiber is shortened, which could be benefit for constructing compact or ultra-compact inline FWM-based sensors. Furthermore, the FWM-based temperature sensor also presented good stability against the fluctuation of the excited power.

A four-wave mixing (FWM)-based refractive index sensor for potential microfluid sensing applications was proposed and analyzed in theory and experiment. The RI sensitivity of 6238.90 nm/RIU was obtained with a highly nonlinear microstructured fiber shortened to 60 mm, and the RI sensing resolution is as high as 2.2 x 10(-5) RIU. By choosing an appropriate wavelength domain, the signal wavelength for RI sensing is considerably more stable, and the sensing figure of merit is much higher than others. Finally, an inline FWM-based microfluid RI sensor with microslot structures constructed by femtosecond laser ablation was fabricated successfully. (C) 2019 The Japan Society of Applied Physics

We investigate the Fresnel zone plate (FZP) inscribed on multimode fiber endface using femtosecond laser ablation and its application in sensing. The mode transmission through fiber tips with FZP is investigated both by the beam propagation method theoretically and by measuring the beam images with a charge-coupled device camera experimentally, which show a good agreement. Such devices are tested for surface-enhanced Raman scattering (SERS) using the aqueous solution of rhodamine 6G under a Raman spectroscopy. The experimental results demonstrate that the SERS signal is enhanced benefiting from focal ability of FZP, which is a promising method for the particular biochemical spectra sensing applications. (C) 2018 Society of PhotoOptical Instrumentation Engineers (SPIE).

A novel one-step calibration method with no iteration and high trimming accuracy for on-chip oscillator is proposed. The concept is to count oscillator cycles within a specified reference period of time, and take the count value as the trimming code of oscillator to achieve the targeted frequency. To demonstrate the effectiveness of this method, an on-chip RC relaxation oscillator with 8-bits trimming signal has been designed, analyzed and verified with a 0.5um CMOS technology. Simulation results show that the oscillator achieves a low frequency variation of ±0.8% over ±45% process variation of resistor and capacitor after one-step calibration.

An ultrasensitive refractive index sensor based on the four-wave mixing in a suspended-core microstructured fiber (SC-MOF) is proposed. It presents that, due to much power penetration into the air holes of the SC-MOF, the refractive index (RI) sensitivity is up to 2.43 x 10(5) nm/RIU for the produced idler wave of the four-wave mixing in SC-MOF. The RI responses of idler wave and signal wave are analyzed as pump wavelengths locate in the normal dispersion region and anomalous dispersion region, respectively. The simulation results show that, if the pump wavelength locates in normal dispersion region and the idler wave is used for wavelength-encoded demodulation, it would be more appropriate for RI sensing. The influence of incident power on RI sensitivity, power fluctuation induced RI measurement error and sensing quality are also analyzed. It is demonstrated that moderate incident power must be selected, and pump wavelength away from transition point would be beneficial for RI measurement stability.

In this paper, a simplified hollow-core photonic crystal fiber surface-enhanced Raman scattering (SERS) probe is presented. Silver nanoprisms are grown with a photoreduction method and account for the SERS, which have better electromagnetic enhancement than spherical silver nanoparticles at 785 nm. Due to the antiresonant reflecting guidance mechanism, the excited laser and SERS signal are effectively guided in such a fully filled hollow-core photonic crystal fiber SERS probe and complicated selective filling with target sample is avoided. Rhodamine 6G molecules are used as probe molecules and the simplified hollow-core photonic crystal fiber SERS probe is test. Detection of low concentration Rhodamine 6G down to 10−8 M is achieved with a short integration time of 300 ms.

This manuscript presents a new bandgap reference (BGR) circuit providing dual references of voltage and current in one BGR circuit. The proposed all-in-one BGR circuit combines two proportional to absolute temperature (PTAT) current branches of conventional BGR into one NMOS transistor, avoiding the mismatch of the current branches. It also generates a new complementary proportional to absolute temperature (CTAT) current by adding a positive temperature coefficient (PTC) resistor to BGR output. Combining the two opposite TC currents together, a temperature insensitive current reference with robust zero TC point against process variation can be obtained in one BGR circuit. The BGR circuit is designed and verified in a 0.5μm CMOS technology with an active area of 0.0165mm 2 . With 3.3-V supply voltage, the BGR circuit provides voltage and current reference of 1.25V and 13.5uA with TCs of 11.6ppm/°C and 58.5ppm/°C over the temperature range from -40°C to 85°C, respectively.

This paper demonstrates an improved laser-induced deposition of silver nanoparticles method based on fiber surface micro-grating for surface-enhanced Raman scattering (SERS). The femtosecond (fs) laser ablation is used to create a roughened surface with micro-grating structures on the cleaved fiber end, which is beneficial for silver nanoparticles growth, and then the end of the fiber probe is immersed in a reaction solution for deposition of silver nanoparticles with a 785 nm exciting laser beam coupled into the fiber probe. The experiment results show that a larger number of silver nanoparticles have deposited on the roughed end using laser-induced method compared with the flat fiber end under the same induction conditions, leading to a better performance for the R6G molecules detection (about 32 times). Our rapid prepared fiber SERS probe provides a feasible method for real-time, high performance and remote measurement of the SERS signal in biochemical analysis.

This paper presents a novel U-shaped fiber surface-enhanced Raman scattering (SERS) spectra probe with high-performance remote sensing based on femtosecond laser ablation and deposition of photoreduced silver nanoparticles. As the width of the U-shaped structure is around 12 μm, the sensitivity is enhanced about four times more than that of a single-endface-based fiber SERS probe. The experiment results show that there is a nonlinear relationship between the SERS signal and the width of the U-shaped structure, whereas the SERS signal is sharply decreased with the increasing width of the U-shape. Our U-shaped fiber SERS probe shows a feasible method for high-performance, real-time, and remote measurement of the SERS signal in biochemical analysis.

In this paper, a surface-enhanced Raman scattering (SERS) spectral probe based on a polymethylmethacrylate (PMMA) polymer fiber is produced by femtosecond laser ablation and photoreduced deposition of silver nanoparticles. It shows that a surface grating structure enabled by femtosecond laser ablation could further improve the SERS signal by around four times larger than the ordinarily roughened structure. By varying femtosecond laser pulse energy and scan surface period in the fabrication process, the enhancement factor of the SERS signal is optimized with laser scan surface period of around 5 μm at 1.2 μJ femtosecond laser pulse energy for a PMMA fiber probe. In particular biochemical analysis, much softer SERS probes are preferred, and our polymer SERS fiber probe shows an alternative method for in situ measurement of the SERS signal and further fabrication of polymer SERS microchip.

The ancient Puer tea horse road is one of significant nodes in the ancient Yunnan-Tibet tea horse road. Now By way of site investigation and GIS information technology, using the analytic hierarchy process (AHP) we has carried on the value evaluation and classification, and using GIS software combined with of the adjacent index model has carried on the analysis of space characteristics. The main results are as follows: We have completed the resources composition and value assessment of the linear cultural heritage corridor. And have determined heritages identification and login, and have completed the heritage spatial characteristics analysis. The spatial distribution of heritage is two typical characteristics: between heritage point the spatial agglomeration degree is high and there are significant grade differences. The distance between heritage point and the ancient road within 10 km covers 80 % of the number of heritage, it provide the basis for the width of the protecting corridor.

Surface-enhanced Raman scattering (SERS) probes are made by facile photochemical deposition of silver nanoparticles on a femtosecond (fs) laser ablated, D-shaped fiber. The structure and surface morphology of the probe are investigated by scanning electron microscopy. High-quality SERS signals are detected using Rhodamine 6G molecules via an in situ sensing mode. Experimental results show that the SERS signals increase with the increase of the length of fs laser ablated, D-shaped zone. Our D-shaped fiber SERS probe shows a feasible method for a large active area, high performance, and real-time and remote measurement of SERS signals in biochemical analysis.

We experimentally demonstrate a novel reflective temperature-insensitive all-fiber pressure sensor based on polarization-maintaining photonic crystal fiber (PM-PCF). The sensing head is composed of a small segment of PM-PCF and a leading single-mode fiber (SMF). Two orthogonal polarized modes in the PM-PCF are excited by the splice point between SMF and the PM-PCF. After a round trip along the PM-PCF, a phase difference between two orthogonal polarization modes is induced due to the intrinsic high-birefringence of PM-PCF, and a Michelson-type reflective polarization-mode interferometer is enabled. The experimental results demonstrate that the wavelength-pressure coefficient of 4.15nm/MPa can be achieved, while the temperature coefficient is only 1.4pm/°C. This type of pressure sensor offers salient advantages of high wavelength-pressure coefficient, low cross sensitivity to temperature, compact size, robust structure, and flexibility in application.

We present an approach for manufacturing liquid-core microstructured optical fiber (MOF) with an all-in-fiber configuration. The MOF is first fusion-spliced with conventional fiber pigtails, with channels left open at the spliced interfaces to allow filling. After liquid filling, the channels are sealed by adhesives to prevent evaporation of the liquid. To verify the efficacy of this method, we filled a simplified hollow-core MOF (SHC-MOF) with a solution of aqueous quantum dots, and the temperature characteristics of the filled SHC-MOF were measured. The fluorescent peak wavelength and intensity changed reversibly over 48 h of repeated temperature cycling, indicating that the all-in-fiber configuration of the integrated liquid-core SHC-MOF has long-term stability and that the evaporation of the filling solution is minimal.

Quantum dots (QDs)-based multiplexed fiber-optic temperature sensors are proposed for multi-point sensing, which are composed of hollow-core microstructured optical fibers filled with aqueous QDs solutions of different fluorescent wavelengths. A parallel reflective configuration is adopted to avoid the crosstalk of fluorescent emissions, and to construct practical probes. Temperature experiments show that the fluorescent peak wavelength and the self-referenced intensity of two sensors both change with temperature linearly in the range from -10 °C to 120 °C with favorable reversibility. At last, the crosstalk of both the fluorescent peak wavelength and the self-referenced intensity of two sensors is tested for in the range of the temperature measurements.

A simple and compact interferometer for temperature and pressure discrimination is proposed and demonstrated experimentally. It consists of a short section of high-birefringence photonic crystal fiber (Hi-Bi PCF) and a cascaded fiber Bragg grating (FBG). In the Hi-Bi PCF, two orthogonal polarized modes are employed as optical arms to construct, such as a Michelson interferometer. Combined with a cascaded FBG, pressure and temperature measurements are discriminated by a matrix method, and the pressure sensitivity of Hi-Bi PCF is determined to be around 3.65 nm/MPa. The proposed Michelson interferometer is easy-to-fabricate, flexible, and low-cost, which shows great potential in future applications of remote sensing. (C) 2016 Society of Photo-Optical Instrumentation Engineers (SPIE)

The morphological evolution of polyhedral Cu2O crystals and the LSPR and SERS characteristics of the as-synthesized polyhedral Cu2O@Ag CMs with different structures.