Yukun Han

Temperature-insensitive miniaturized fiber inline Fabry-Perot interferometer for highly sensitive refractive index measurement

We report a miniaturized fiber inline Fabry-Perot interferometer (FPI), with an open micro-notch cavity fabricated by one-step fs laser micromachining, for highly sensitive refractive index measurement. The device was tested for measurement of the refractive indices of various liquids including isopropanol, acetone and methanol at room temperature, as well as the temperature-dependent refractive index of deionized water from 3 to 90 degrees C. The sensitivity for measurement of refractive index change of water was 1163 nm/RIU at the wavelength of 1550 nm. The temperature cross-sensitivity of the device was about 1.1x10(-6) RIU/degrees C. The small size, all-fiber structure, small temperature dependence, linear response and high sensitivity, make the device attractive for chemical and biological sensing.

Miniaturized Fiber Inline Fabry-Perot Interferometer Fabricated with a Femtosecond Laser

We report a miniaturized inline Fabry-Perot interferometer directly fabricated on a single-mode optical fiber with a femtosecond laser. The device had a loss of 16 dB and an interference visibility exceeding 14 dB. The device was tested and survived in high temperatures up to 1100 degrees C. With an accessible cavity and all-glass structure, the new device is attractive for sensing applications in high-temperature harsh environments.

Surface-enhanced Raman-scattering fiber probe fabricated by femtosecond laser.

We report what we believe to be a new method to fabricate surface enhanced Raman scattering (SERS) fiber probe by direct femtosecond laser micromachining. Direct femtosecond laser ablations resulted in nanostructures on the cleaved endface of a multimode optical fiber with a 105/125 microm core/cladding diameter. The laser-ablated fiber endface was SERS activated by silver chemical plating. High-quality SERS signal was detected using Rhodamine 6G molecules (10(-8)-10(-6) M solutions) via back excitation with the fiber length of up to 1 m. The fiber SERS probe was compared with a planar fused silica substrate at a front excitation. The long lead-in fiber length and the backexcitation/collection setup make the SERS probe promising for remote sensing applications.

Optical fiber sensors for high temperature harsh environment sensing

This paper summarizes our recent research progresses in developing optical fiber harsh environment sensors for monitoring the operating conditions of a coal-fired power plant and in-situ detection of key gas components in coal-derived syngas. The sensors described in this paper include a miniaturized inline fiber Fabry-Perot interferometer (FPI) fabricated by one-step femtosecond (fs) laser micromachining, a long period fiber grating (LPFG) and a fiber inline core-cladding mode interferometer (CMMI) fabricated by controlled CO2 laser irradiations. Their operating principles, fabrication methods, and applications for measurement of various physical and chemical parameters in a high temperature and high pressure coexisting harsh environment are presented.

Miniaturized fiber inline Fabry-Pérot interferometer for chemical sensing

This paper demonstrates the chemical sensing capability of a miniaturized fiber inline Fabry-Pérot sensor fabricated by femtosecond laser. Its accessible cavity enables the device to measure the refractive index within the cavity. The refractive index change introduced by changing the acetone solution concentration was experimentally detected with an error less than 4.2×10-5.

Measurement of Refractive Index Change of Optical Fiber Core Induced by Femtosecond Laser Scanning

We report a new method to measure the refractive index change in optical fiber core induced by femtosecond (fs)laser exposure. An in-line Fabry-Perot interferometer, serving as the measurement platform, is constructed on a commercial single-mode optical fiber by one-step femtosecond (fs) laser fabrication. A positive refractive index change is observed and measured accurately as the laser pulse energy surpasses the ablation threshold.

Optical fiber sensors for high temperature harsh environment applications

This paper summarizes our recent research progresses in developing optical fiber harsh environment sensors for various high temperature harsh environment sensing applications such as monitoring of the operating conditions in a coal-fired power plant and in-situ detection of key gas components in coal-derived syngas. The sensors described in this paper include a miniaturized inline fiber Fabry-Perot interferometer (FPI) fabricated by one-step fs laser micromachining, a long period fiber grating (LPFG) and a fiber inline core-cladding mode interferometer (CMMI) fabricated by controlled CO2 laser irradiations. Their operating principles, fabrication methods, and applications for measurement of various physical and chemical parameters in a high temperature and high pressure coexisting harsh environment are presented.

Optical Fiber Sensors for Harsh Environment Monitoring

This paper summarizes our recent research progresses in developing optical fiber harsh environment sensors for monitoring the operating conditions of a coal-fired power plant and in-situ detection of key gas components in coal-derived syngas. The sensors described in this paper include a miniaturized inline fiber Fabry-Perot interferometer (FPI) fabricated by one-step fs laser micromachining, a long period fiber grating (LPFG) and a fiber inline core-cladding mode interferometer (CMMI) fabricated by controlled CO 2 laser irradiations. Their operating principles, fabrication methods, and applications for measurement of various physical and chemical parameters in a high temperature and high pressure coexisting harsh environment are presented.

Temperature-Insensitive Miniaturized Fiber Inline Fabry-Perot Interferometer Fabricated by Femtosecond Laser

This article presents a miniaturized fiber inline Fabry-Perot interferometer (FPI), with an open micro-notch cavity fabricated by one-step femtosecond (fs) laser micromachining, for highly sensitive refractive index measurement. The device was tested for measurement of the refractive indices of various liquids including isopropanol, acetone and methanol at room temperature, as well as the temperature-dependent refractive index of deionized water from 3 to 90°C. The sensitivity for measurement of refractive index change of water was 1163 nm/RIU at the wavelength of 1550 nm. The temperature cross-sensitivity of the device was about 1.1×10−6 RIU/°C. The small size, all-fiber structure, small temperature dependence, linear response and high sensitivity, make the device attractive for chemical and biological sensing.Copyright

Femtosecond Laser-Induced Silicon Surface Morphology in Water

This article investigates the use of femtosecond laser induced surface morphology on silicon wafer surface in water confinement. Unlike irradiation of silicon surfaces in the air, there are no laser induced periodic structures, but irregular roughness is formed when the silicon wafer is ablated under water. The unique discovery of a smoothly processed silicon surface in water confinement under certain laser parameter combinations may help improve laser direct micromachining surface quality in industrial applications.© 2008 ASME