Xinran Dong

Superamphiphobic miniature boat fabricated by laser micromachining

We fabricated a superamphiphobic miniature boat with marked drag reduction and excellent loading capacity using femtosecond laser direct writing technology. The as-prepared superamphiphobic surface of the boat exhibited apparent contact angles larger than 150° toward both water and oil. Miniature boats with the superamphiphobic surface slid effortlessly on both water and oil-polluted water surfaces, with an increase in sliding distance by up to 52% and load increase of up to 27% compared with those of a boat with an untreated surface. A potential mechanism that explains the excellent performance of the superamphiphobic miniature boat was also discussed. This work provides a simple and economically viable strategy to obtain advanced surfaces for use in microfluidics and marine engineering.

Underwater superoleophobicity, anti-oil and ultra-broadband enhanced absorption of metallic surfaces produced by a femtosecond laser inspired by fish and chameleons.

Reported here is the bio-inspired and robust function of underwater superoleophobic, anti-oil metallic surfaces with ultra-broadband enhanced optical absorption obtained through femtosecond laser micromachining. Three distinct surface structures are fabricated using a wide variety of processing parameters. Underwater superoleophobic and anti-oil surfaces containing coral-like microstructures with nanoparticles and mount-like microstructures are achieved. These properties of the as-prepared surfaces exhibit good chemical stability when exposed to various types of oils and when immersed in water with a wide range of pH values. Moreover, coral-like microstructures with nanoparticle surfaces show strongly enhanced optical absorption over a broadband wavelength range from 0.2–25 μm. The potential mechanism for the excellent performance of the coral-like microstructures with a nanoparticle surface is also discussed. This multifunctional surface has potential applications in military submarines, amphibious military aircraft and tanks, and underwater anti-oil optical counter-reconnaissance devices.

Robust laser-structured asymmetrical PTFE mesh for underwater directional transportation and continuous collection of gas bubbles

We report a simple, efficient method to fabricate micro/nanoscale hierarchical structures on one side of polytetrafluoroethylene mesh surfaces, using one-step femtosecond laser direct writing technology. The laser-treated surface exhibits superhydrophobicity in air and superaerophilicity in water, resulting in the mesh possessing the hydrophobic/superhydrophobic asymmetrical property. Bubbles can pass through the mesh from the untreated side to the laser-treated side but cannot pass through the mesh in the opposite direction. The asymmetrical mesh can therefore be designed for the directional transportation and continuous collection of gas bubbles in aqueous environments. Furthermore, the asymmetrical mesh shows excellent stability during corrosion and abrasion tests. These findings may provide an efficient route for fabricating a durable asymmetrical mesh for the directional and continuous transport of gas bubbles.

Highly Sensitive Strain Sensor Based on a Novel Mach-Zehnder Interferometer with TCF-PCF Structure

A highly sensitive strain sensor based on a novel fiber in line Mach-Zehnder interferometer (MZI) was demonstrated experimentally. The MZI was realized by splicing a section of photonic crystal fiber (PCF) with the same length of thin core fiber (TCF) between two single mode fibers (SMFs). The fringe visibility of MZI can reach as high as 20 dB in air. In particular, the strain sensitivity of −1.95 pm/με was achieved within a range from 0 to 4000 με. Furthermore, the strain properties of different length of MZI was investigated. It was found that the sensitivity was weekly dependent on the length of MZI. The strain sensitivities corresponding to the MZI with 35 mm PCF, 40 mm PCF and 45 mm PCF at 1550 nm band were −1.78 pm/με, −1.73 pm/με and −1.63 pm/με, respectively. Additionally, the sensor has advantages of simple fabrication, compact size and high sensitivity as well as good fringe visibility.

A Novel Strain Sensor with Large Measurement Range Based on All Fiber Mach-Zehnder Interferometer

We have proposed a high sensitive photonic crystal fiber (PCF) strain sensor based on the Mach-Zehnder interferometer (MZI). The sensing head is formed by all-fiber in-line single mode-multimode-photonic-crystal-single mode fiber (SMPS) structure, using only the splicing method. Such a strain sensor exhibited a high sensitivity of −2.21 pm/με within a large measurement range of up to 5000 με and a large fringe visibility of up to 24 dB. Moreover, it was found that the strain sensitivity was weekly dependent of the length of PCF or MMF. In addition, the sensor exhibited the advantages of simplicity of fabrication, high sensitivity and larger fringe visibility.

Underwater giant enhancement of broadband diffraction efficiency of surface diffraction gratings fabricated by femtosecond laser

In this study, a simple approach is proposed to improve the diffraction efficiency of surface diffraction gratings on fused silica fabricated by femtosecond laser. Effects of grating period, pulse energy, scanning speed and wavelength on the total diffraction efficiency are also investigated. In addition, the mechanism of the diffraction efficiencys giant enhancement is discussed by finite difference time domain (FDTD) and optical phase shift structure calculation. It is revealed that: (1) Compared with the diffraction efficiency obtained in air, the underwater image via diffraction grating is clearer than that in air and diffraction pattern in water is much brighter; (2) The diffraction efficiency increases with an increase in wavelength and scanning speed, whereas it decreases while the laser pulse energy is high; and (3) This giant enhancement is attributed to the degree of Mie scattering and refraction, which is effectively reduced for the existence of water.

Temperature sensitivity enhancement of platinum-nanoparticle-coated long period fiber gratings fabricated by femtosecond laser

The temperature sensing performance of long period fiber gratings (LPFGs) written by femtosecond laser pulses coated with platinum nanoparticles (PtNPs) is proposed and demonstrated. It is found that the PtNPs increase the wavelength sensitivity of the LPFG significantly compared with the bare LPFG. The temperature sensitivities of the bare LPFG for three dips, corresponding to 1438, 1485, and 1585 nm, are 74.04, 77.23, and 86.26  pm/°C, respectively, when the temperature changes from 10°C to 500°C, whereas the corresponding sensitivities of PtNP coated LPFGs are up to 90.58, 93.51, and 103.43  pm/°C, respectively. Moreover, the PtNP coated LPFG has shown better wavelength repeatability. A small wavelength hysteresis of ∼0.5  nm is observed when the temperature is less than 300°C.

Microcavity Mach–Zehnder Interferometer Sensors for Refractive Index Sensing

Two types of robust Mach-Zehnder interferometer (MZI) sensors based on microcavity in a single mode optical fibers (SMFs) are proposed, which are fabricated by femtosecond laser inscription and chemical etching. The SMFs are modified by an improved point-by-point inscription method (called a transversal-scanning method) or a line-by-line scanning inscription method, which lead to form a rectangular-shaped or a V-shaped MZI after etching. The MZIs show high refractive index (RI) sensitivity above 105 nm/RIU with good linearity. Especially, the rectangular-shaped MZI exhibits a ultra-high RI sensitivity of -17503.73 nm/RIU with a linearity of 0.999 in the range of 1.3371-1.3407. The results of which are coincident with theoretical calculation. In addition, the MZI structures have good mechanical strength and temperature sensitivities in water are also studied.

Quasi-periodic concave microlens array for liquid refractive index sensing fabricated by femtosecond laser assisted with chemical etching

In this study, a high-efficiency single-pulsed femtosecond laser assisted with chemical wet etching method has been proposed to obtain large-area concave microlens array (MLA). The quasi-periodic MLA consisting of about two million microlenses with tunable diameter and sag height by adjusting laser scanning speed and etching time is uniformly manufactured on fused silica and sapphire within 30 minutes. Moreover, the fabricated MLA behaves excellent optical focusing and imaging performance, which could be used to sense the change of the liquid refractive index (RI). In addition, it is demonstrated that small period and high RI of MLA could acquire high sensitivity and broad dynamic measurement range, respectively. Furthermore, the theoretical diffraction efficiency is calculated by the finite domain time difference (FDTD) method, which is in good agreement with the experimental results.

Simultaneous Strain and Temperature Sensor Based on a Fiber Mach-Zehnder Interferometer Coated with Pt by Iron Sputtering Technology

We demonstrated a fiber in-line Mach-Zehnder interferometer (MZI) coated with platinum (Pt) for the simultaneous measurement of strain and temperature. The sensor was fabricated by splicing a section of multimode fiber (MMF) between two single mode fibers (SMFs) and the Pt coating was prepared by iron sputtering technology. Fine interference fringes of over 20 dB with a compact size of 20 mm were achieved. The experimental results of the two different resonant dips showed strain sensitivities of −2.06 pm/με and −2.21 pm/με, as well as temperature sensitivities of 55.2 pm/°C and 53.4 pm/°C, respectively. Furthermore, it was found that the Pt coating can improve the strain sensitivity significantly, resulting in an increase of about 54.5%. In addition, the sensor has advantages of easy fabrication, low cost, and high sensitivity, showing great potential for the dual-parameter sensing of strain and temperature.