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Published on: January 29, 2013
Far-field evanescent wave propagation using coupled subwavelength gratings for a MEMS sensor
Al-Aakhir A Rogers1, Scott Samson, Sunny Kedia
1University of South Florida, Department of Electrical Engineering, 4202 E. Fowler Ave, Tampa, Florida 33620, USA. aaroger4@mail.usf.edu
Summary
This study demonstrates coupling near-field evanescent waves into far-field diffraction orders using coupled gratings. This technique enhances diffraction for applications like microelectromechanical systems (MEMS) accelerometers.
Area of Science:
- Optics and Photonics
- Nanotechnology
- Materials Science
Background:
- Subwavelength gratings typically interact with light in the near-field.
- Coupling gratings can create effective periods that are not subwavelength.
- Evanescent waves are confined to the surface and decay exponentially.
Purpose of the Study:
- To develop a technique for coupling near-field evanescent waves into far-field diffraction orders.
- To investigate the use of coupled gratings with different materials (glass and silicon).
- To explore the application of this evanescent wave coupling in MEMS accelerometers.
Main Methods:
- Fabrication of two gratings with subwavelength periods (1.0 µm in glass, 1.1 µm in silicon).
- Coupling these gratings to achieve an 11.0 µm effective grating period.
- Simulating optimum evanescent wave coupling by varying grating thickness and separation.
Main Results:
- The coupled gratings exhibited an 11.0 µm effective period, which is not subwavelength for a 1.550 µm infrared source.
- Higher diffraction orders were observed due to the effective grating period.
- Simulations identified optimal parameters for evanescent wave coupling efficiency.
Conclusions:
- A novel technique for evanescent wave coupling into far-field diffraction orders was successfully developed.
- The coupled grating system shows potential for enhanced light manipulation.
- This evanescent wave coupling concept is a promising candidate for integration into bulk silicon MEMS accelerometers.
