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

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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*

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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

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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

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¼ Wave-Plate

½ CellFull Cell

λ = 795nm

½ Wave-Plate VCSEL

Power Split Ratio

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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

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Sensor

VCSEL

½ NMR Cell

Results of 6-Layer Wafer

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VCSEL

6 Layer Wafer

Sensor

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Analysis Results of the 6-Layer Cell

E0x

Sensor

VCSEL

½ NMR Cell

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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

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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?