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Study of Factors Affecting Performance of Spin-Polarized
Atomic Gyroscopes Uyen Nguyen HuynhDr. Andrei M. Shkel
Max PerezJesper Eklund Monty Rivers
Ilya N. ChepurkoMarc Salleras
IM-SURE
• Introduction • Motivation• Background on Thin-film Design• Background on Polarized Light• Procedure• Results• Conclusion
Outline
2
Introduction
• NMRG: Nuclear Magnetic Resonance Gyroscope
• Requires circularly polarized light and high optical power
• Interest: optical properties at various α
Static Field Bo
B1cos(ωat)
Cross-section of assembled NMRG*
3
Drawing by Jesper Eklund* John Kitching, Elizabeth Donley, Andrei M. Shkel, E. Jesper Eklund, and Eleanor Hodby, "Compact Atomic Magnetometer and Gyroscope Based on a Diverging Laser Beam," UC Case No. 2008-002, Patent pending.
VCSEL
Photodiode
NMR Cell
• Coated with alternating layers of high and low indices of refraction
• Filled with NMR gas
1.8mm
4Graphics and fabricated by Max Perez
• NMR Gyroscope performance affected by:
– Circularly polarized light
– Intensity of reflected light
• Study the effects of multilayer reflectors and fabrication imperfection on reflectance and polarization state of light
Motivation
5
Why Multi-Layer Thin-Film?
nH*LH = nL*LL = λair/4
6Image from http://en.wikipedia.org/wiki/Image:Optical-coating-2.png
L LAir H H Si
Polarization States
Image from http://www.thorlabs.com/Thorcat/12900/12973-D02.pdf 7
Poincare Sphere Sensor Sample
Experimental Procedure
8
¼ Wave-Plate
½ CellFull Cell
λ = 795nm
½ Wave-Plate VCSEL
Power Split Ratio
9
Circularly Polarized light:• a = 0.5• ∆ = ± 90o
Image from http://www.thorlabs.com/Thorcat/12900/12973-D02.pdf
• Power Split Ratio: 0 ≤ a ≤ 1• Phase difference: -180o ≤ ∆ ≤ 180o
• Bulk Silicon cell
• 12 Si3N4-SiO2 layer cell (n = 2.0, 1.5)
• 8 Si-SiO2 layer cell (n = 3.7, 1.5)
• 6 Si-SiO2 layer cell
• 6 Si-SiO2 layer wafer
Test Samples
Graphics and fabricated by Max Perez 10
Results of 6-Layer Cell
11
Sensor
VCSEL
½ NMR Cell
Results of 6-Layer Wafer
12
VCSEL
6 Layer Wafer
Sensor
13
Analysis Results of the 6-Layer Cell
E0x
Sensor
VCSEL
½ NMR Cell
14
Intensity of First Reflection
VCSEL
Results of Double Reflection
Graph and samples by Max Perez 15
• Multi-layer thin-film design:
– Improves cell’s reflectance to ~ 99%
– Able to keep circularly polarized light inside cell
• Fabrication imperfection:
– Decreases reflectance of NMR cell
– Varies phase difference significantly
– Changes the polarization state of light inside cell
– Improves reflectance compared to bulk Si cell
Conclusion
16
Acknowledgements
NATIONAL SCIENCE FOUNDATION
IM-SURE Managing Director :
Said M. Shokair
Faculty Mentor:
Andrei M. Shkel, PhD.
MicroSystems Lab
Max Perez
Jesper Eklund
Monty Rivers
Ilya N. Chepurko
Marc Salleras 17
Questions?