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

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 B o B 1 cos(ω a t) 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 , Patent pending. VCSEL Photodiode

NMR Cell Coated with alternating layers of high and low indices of refraction Filled with NMR gas 1.8mm 4 Graphics 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? n H *L H = n L *L L = λ air /4 6 Image from LLAirHHSi

Polarization States Image from 7

Poincare SphereSensorSample Experimental Procedure 8 ¼ Wave-Plate ½ CellFull Cell λ = 795nm ½ Wave-PlateVCSEL

Power Split Ratio 9 Circularly Polarized light: a = 0.5 ∆ = ± 90 o Image from Power Split Ratio: 0 ≤ a ≤ 1 Phase difference: -180 o ≤ ∆ ≤ 180 o

Bulk Silicon cell 12 Si 3 N 4 -SiO 2 layer cell (n = 2.0, 1.5) 8 Si-SiO 2 layer cell (n = 3.7, 1.5) 6 Si-SiO 2 layer cell 6 Si-SiO 2 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 E 0x 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?

Reflected Polarized Light S_wave: perpendicular to incident plane P_wave: parallel to incident plane 19 Incident light Reflected light Refracted light θiθi Air Si ( )

Power Split Ratio a = I * ~ E * ( ) R S * I oS R P * I oP 2 Power Split Ratio and Reflectance

Results of Si Cell 21 E 0x Sensor VCSEL ½ NMR Cell