Study of Factors Affecting Performance of SpinPolarized Atomic

Study of Factors Affecting Performance of Spin-Polarized Atomic Gyroscopes Uyen Nguyen Huynh Dr. Andrei M. Shkel Max Perez Jesper Eklund Monty Rivers Ilya N. Chepurko Marc Salleras IM-SURE

Outline • • Introduction Motivation Background on Thin-film Design Background on Polarized Light Procedure Results Conclusion 2

Introduction B 1 cos(ωat) • NMRG: Nuclear Magnetic Resonance Gyroscope • Requires circularly polarized light and high optical power • Interest: optical properties at various α Static Field Bo Cross-section of assembled NMRG* Photodiode VCSEL 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. 3

NMR Cell • Coated with alternating layers of high and low indices of refraction • Filled with NMR gas 1. 8 m m Graphics and fabricated by Max Perez 4

Motivation • 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 5

Why Multi-Layer Thin-Film? Air H L Si n. H*LH = n. L*LL = λair/4 Image from http: //en. wikipedia. org/wiki/Image: Optical-coating-2. png 6

Polarization States Image from http: //www. thorlabs. com/Thorcat/12900/12973 -D 02. pdf 7

Experimental Procedure Poincare Sphere Sensor Sample ¼ Wave-Plate ½ Wave-Plate VCSEL λ = 795 nm Full Cell ½ Cell 8

Power Split Ratio • Power Split Ratio: 0 ≤ a ≤ 1 • Phase difference: -180 o ≤ ∆ ≤ 180 o Circularly Polarized light: • a = 0. 5 • ∆ = ± 90 o Image from http: //www. thorlabs. com/Thorcat/12900/12973 -D 02. pdf 9

Test Samples • • • Bulk Silicon cell 12 Si 3 N 4 -Si. O 2 layer cell (n = 2. 0, 1. 5) 8 Si-Si. O 2 layer cell (n = 3. 7, 1. 5) 6 Si-Si. O 2 layer cell 6 Si-Si. O 2 layer wafer Graphics and fabricated by Max Perez 10

Results of 6 -Layer Cell ½ NMR Cell Sensor VCSEL 11

Results of 6 -Layer Wafer 6 Layer Wafer Sensor VCSEL 12

Analysis Results of the 6 -Layer Cell Sensor ½ NMR Cell VCSEL E 0 x 13

Intensity of First Reflection VCSEL 14

Results of Double Reflection Graph and samples by Max Perez 15

Conclusion • 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 16

Acknowledgements NATIONAL SCIENCE FOUNDATION IM-SURE Managing Director : Said M. Shokair Faculty Mentor: Andrei M. Shkel, Ph. D. Micro. Systems Lab Max Perez Jesper Eklund Monty Rivers Ilya N. Chepurko Marc Salleras 17

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