FEMTOSECOND LASER FABRICATION OF MICRO/NANO-STRUCTURES FOR
CHEMICAL SENSING AND DETECTION
Student: Yukun Han
Introduction and Background
Dr. Hai-Lung Tsai
Dr. Hai Xiao
Results-SERS Substrate on Silicon
Femtosecond Laser System
Femtosecond Laser Micromachining Advantages:
Major Parameters of Ti: Sapphire Femtosecond Laser System
Pulse Width: 120 fs
Minimum Spot Size: < 1 m
Wavelength: 300 nm3000 nm
Pulse Energy: 1 mJ
Capable of processing any
Spatial Mode: TEM00
2AgNO3 2Ag + 2NO2 + O2
Average Power: 1 W
5-axis CNC Operations
Repetition Rate: 1 kHz
One-Step Fabrication of Silicon SERS Substrate
AgNO3 for 10
Improved 3D resolution
Results- SERS Substrate on Fused Silica
Scanning Electron Microscopy Images of Silicon SERS Substrate
Surface Enhanced Roman Scattering (SERS) Background
Raman scattering is an inelastic scattering of photons for materials
SERS is a surface sensitive technique : The largest enhancements occur
for metal (e.g., silver, gold, copper) surfaces which are rough on the
Fiber SERS Probe Fabrication
Scanning Electron Microscopy Images of A Fiber Probe
Wave Plate Polarizer Filter Shutter
(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
(a) freshly cleaved fiber in a 10-3 M solution,
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.
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.
(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)
(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
Repetition Rate: 1 kHz
(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).
SERS enhancement factor
I SERS N nR
I nR N SERS
Working on investigating the laser-silicon interaction mechanisms that
lead to the SERS enhancement.
Designing sensors for further chemical and bio applications.
The research work was supported by Intelligent Systems Center,
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