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Electrically tunable coherent optical absorption in graphene with ion gel
Vrinda Thareja1, Ju-Hyung Kang, Hongtao Yuan
1Geballe Laboratory for Advanced Materials, Stanford University , Stanford, California 94305, United States.
Nano Letters
|February 12, 2015
Summary
Researchers achieved electrical control over light absorption using a graphene Salisbury screen. This novel device significantly enhances optical absorption and demonstrates a record-high electrically induced change in absorption for atomically thin materials.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Nanotechnology
Background:
- Graphene exhibits unique optical properties, making it a candidate for advanced optical devices.
- Salisbury screens are resonant structures designed to enhance light absorption.
- Electrical control over optical properties is crucial for tunable photonic applications.
Purpose of the Study:
- To demonstrate electrical control over coherent optical absorption in a graphene-based Salisbury screen.
- To investigate the enhancement of light absorption at a specific wavelength (3.2 μm).
- To achieve significant electrically induced changes in graphene's optical absorption.
Main Methods:
- Fabrication of a graphene Salisbury screen with a silica spacer and gold back reflector.
- Utilizing an ionic gel for electrical gating of graphene's charge density.
- Performing in situ spectroscopic reflectance measurements as a function of gate bias.
- Analyzing reflectance data using a Fresnel-based transfer matrix model with graphene conductivity from the Kubo formula.
Main Results:
- Achieved optical absorption enhancements up to 5.5 times compared to suspended graphene.
- Demonstrated electrically induced changes in optical absorption of ~3.3% per volt, the highest for atomically thick layers.
- Observed a 40% boost in absorption due to a coherent absorption effect linked to the ionic gel layer.
Conclusions:
- Electrical gating provides effective control over coherent optical absorption in graphene Salisbury screens.
- The ionic gel enables efficient gating and contributes to enhanced absorption effects.
- This work presents a promising pathway for developing highly tunable and efficient optical devices based on graphene.
