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

Poster TemplateStudent: Yukun Han MAE Department
Faculty Advisors: Dr. Hai-Lung Tsai MAE Department
Dr. Hai Xiao ECE Department
Introduction and Background
Pulse Width: 120 fs
Pulse Energy: 1 mJ
Repetition Rate: 1 kHz
Average Power: 1 W
Spatial Mode: TEM00
5-axis CNC Operations
One-Step Fabrication of Silicon SERS Substrate
Results-SERS Substrate on Silicon
Conclusion
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.
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 5.4×105.
The high controllability and high efficient femtosecond laser fabrication make the miniaturized sensors attractive for many applications in chemical and biological sensing.
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.
Minimal heat-affected-zone
High precision
Improved 3D resolution
Results- SERS Substrate on Fused Silica
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,
(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).
Femtosecond Laser Micromachining
SERS Signals Detection
Raman scattering is an inelastic scattering of photons for materials analysis
SERS is a surface sensitive technique : The largest enhancements occur for metal (e.g., silver, gold, copper) surfaces which are rough on the nanoscale.
Fiber SERS Probe Fabrication
SERS enhancement factor (EF) calculation:
Scanning Electron Microscopy Images of Silicon SERS Substrate
(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.
(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.
EF was estimated to be 5.4×105
500µm
ND
Filter
l/2
AgNO3 film
Objective lens
Silicon SERS substrate