Poster Template - Intelligent Systems Center

Poster Template - Intelligent Systems Center

FEMTOSECOND LASER FABRICATION OF MICRO/NANO-STRUCTURES FOR
CHEMICAL SENSING AND DETECTION
Student: Yukun Han

Faculty Advisors:

MAE Department

Introduction and Background

Dr. Hai-Lung Tsai
Dr. Hai Xiao

MAE Department
ECE Department

Results-SERS Substrate on Silicon

Femtosecond Laser System

Femtosecond Laser Micromachining Advantages:

Major Parameters of Ti: Sapphire Femtosecond Laser System
Pulse Width: 120 fs

Minimal heat-affected-zone

Minimum Spot Size: < 1 m Wavelength: 300 nm3000 nm High precision Pulse Energy: 1 mJ Capable of processing any Spatial Mode: TEM00 Objective lens Silicon SERS substrate AgNO3 film Laser ablation of silicon 2AgNO3 2Ag + 2NO2 + O2 Average Power: 1 W Periodic structures on silicon Silver particles are reduced from ions 5-axis CNC Operations Repetition Rate: 1 kHz material One-Step Fabrication of Silicon SERS Substrate Immersing in AgNO3 for 10 minutes Coherent Legend Cleaning in acetone Silicon SERS substrate Improved 3D resolution Surface modification Results- SERS Substrate on Fused Silica Scanning Electron Microscopy Images of Silicon SERS Substrate Surface Enhanced Roman Scattering (SERS) Background AgNO3 coating Miniaturization Trend: Raman scattering is an inelastic scattering of photons for materials analysis (Microelectromechanical systems) SERS is a surface sensitive technique : The largest enhancements occur for metal (e.g., silver, gold, copper) surfaces which are rough on the nanoscale. Biotechnology Medical industry Environmental technology Information technology Fiber SERS Probe Fabrication Microelectronics industry Microoptics technology Monitor CCD Silver Chemical Planting (Tollens reaction) SERS Signals Detection Scanning Electron Microscopy Images of A Fiber Probe l/2 ND Wave Plate Polarizer Filter Shutter Coherent OPerA Objective lens (NA 0.3 -0.9) SERS Spectra of R6G (10-6M solution) Raman spectra of Rhodamine 6G (R6G) with a 1.7 mW He-Ne laser excitation power and 1 sec integration time. (a) freshly cleaved fiber in a 10-3 M solution, 250000 Half-wave Plate Optical Parametric Amplifier Periscope Turning mirror 90 Flipper Polarizer Turning mirror Damper ND filters Shutter Camera Intensity (counts) Illuminator d (10) 200000 150000 100000 50000 c a b 0 700 900 1100 1300 Raman shift(cm 50-50 Beam Splitter Humidity meter A fiber probe for SERS detection has been demonstrated by femtosecond laser machining with post chemical silver planting. The enhancement factor of the SERS substrate is up to 106. The high controllability and high efficient femtosecond laser fabrication make the miniaturized sensors attractive for many applications in chemical and biological sensing. Sample (glass, polymer, tissue) Five-axis Stage Conclusion we also present a way to ablate the silicon SERS substrate and reduce the silver ions simultaneously by femtosecond laser pulses. The process confirms the silicon SERS substrate can be completed with one step fabrication with EF of 5.4105. Dichroic mirror Driver (b) Raman spectrum of R6G 10-3M solution on the unablated silicon substrate with pre AgNO3 soaking with an excitation power of 17 mW and integrated time of 2 sec. Raman shift (cm-1) Lamp Computer (a) Raman spectrum of R6G 10-6M solution on laser ablated SERS silicon substrate with an excitation laser power of 1.7 mW and integrated time of 2 sec. EF was estimated to be 5.4105 Experimental Setup Frequency conversion (300nm 3000nm) a 500 m 500m Femtosecond Laser Micromachining Wavelength: 800 nm Pulse Width: 120 fs Repetition Rate: 1 kHz Silicon substrate Intensity (counts) MEMS Coherent Legend Platinum protection coating 1500 1700 (b) fs laser ablated, silver-coated (10 min) fiber SERS probe (1 m long) in a 10-6 M solution, (c) fs laser ablated, silver-coated (10 min) planar fused silica SERS substrate in a 10-6 M solution with front excitation (shifted), and (d) silver-coated (10 min) unroughened fiber (1 m long) in a 10-3 M solution (multiplied by 10). -1) SERS enhancement factor (EF) calculation: I SERS N nR EF I nR N SERS 2.5 10 6 Future Work Working on investigating the laser-silicon interaction mechanisms that lead to the SERS enhancement. Designing sensors for further chemical and bio applications. Acknowledgment The research work was supported by Intelligent Systems Center, Missouri S&T.

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