1. Fabry Perot cavity based microspectrometer • Aamer Mahmood • Donald P. Butler Ph.D. • Department of Electrical Engineering • University of Texas at Arlington, TX 76019 Sponsored by the National Science Foundation

2. Electromagnetic interference • Electromagnetic energy from different sources will interfere when sharing the same space

3. Electromagnetic interference • Interference depends on the phase of each component Constructive interference

4. Incident radiation Reflecting surface Reflecting surface Transmitted radiation A Fabry Perot cavity creates multiple sources with different phase from a single source

5. Interference due to a Fabry Perot cavity • The inter-reflector spacing determines the phase of the transmitted energy • For maximum constructive interference • For maximum destructive interference

6. Broadband incident radiation Narrowband transmitted radiation Fabry Perot cavity based spectrometer • For an inter reflector spacing of , the transmitted radiation will add constructively at

7. Broadband incident radiation amplitude Narrowband transmitted radiation wavelength Tunable Fabry Perot cavity based spectrometer λ0

8. Practical tunable Fabry Perot cavity • Provides mechanical support • Transparent to incident radiation Support layer Metal electrodes Reflecting mirrors • Effect electrostatic actuation • Form Fabry Perot cavity

9. Design Considerations • Optical transmission through support layer • Investigated by measurements • Mechanical displacement of support layer • Investigated by multiphysics FEM simulations • Mechanical strength of support layer • Investigated by multiphysics FEM simulations • Flatness of reflecting mirror during deflection • Investigated by multiphysics FEM simulations

10. Optical transmission through support layer • Optical transmission through the support layer is to be measured • The complex permittivity of the support material has been extracted using Variable angle spectrometery

11. Flat support structure Corrugated support structure to improve flatness Different designs

12. Mechanical displacement of support layer FEM multiphysics simulations

13. Top view of deflected support layer Top view of deflected top mirror Mechanical displacement of corrugated support layer FEM multiphysics simulations

14. Flatness of displaced reflecting mirror (corrugated structure) FEM multiphysics simulations

15. Top view of deflected support layer Top view of deflected top mirror Mechanical displacement of flat support layer FEM multiphysics simulations

16. Flatness of displaced reflecting mirror (flat structure) FEM multiphysics simulations

17. Tunable Fabry Perot cavity based microspectrometer(computer generated model showing support layer) Mises stresses due to displacement Mechanical displacement

18. Tunable Fabry Perot cavity based microspectrometer (computer generated model showing metal surfaces)