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Design, Fabrication, and Experimental Characterization of Plasmonic Photoconductive Terahertz Emitters
Published on: July 8, 2013
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High efficiency photomodulators for millimeter wave and THz radiation
I R Hooper1, N E Grant2, L E Barr3
1Department of Physics and Astronomy, University of Exeter, Stocker Road, Exeter, Devon, EX4 4QL, United Kingdom. i.r.hooper@exeter.ac.uk.
Scientific Reports
|December 5, 2019
Summary
Researchers enhanced silicon photomodulators by orders of magnitude using surface passivation. This breakthrough enables compact, cost-effective modulators for millimeter-wave and terahertz applications, reducing reliance on expensive laser sources.
Area of Science:
- Materials Science
- Optoelectronics
- Photonics
Background:
- Photomodulators are crucial for mm-wave and THz applications.
- Existing photomodulation schemes often overlook the limitations of photoconductive materials.
- Silicon's potential in photomodulation is often limited by surface carrier recombination.
Purpose of the Study:
- To significantly enhance the photomodulation efficiency of silicon.
- To develop cost-effective and compact photomodulators for real-world applications.
- To investigate the impact of surface passivation on silicon's photoconductive properties.
Main Methods:
- Post-treatment of off-the-shelf silicon wafers.
- Surface passivation of silicon wafers using aluminum oxide (Al2O3).
- Characterization of excess carrier lifetimes and photoconductivity.
Main Results:
- Achieved orders of magnitude increase in photomodulation efficiency for silicon.
- Extended excess carrier lifetimes up to ~50 ms by minimizing surface recombination.
- Demonstrated high modulation efficiency (transmission reduced from ~90% to <10%) with low continuous wave excitation intensity (10 Wm-2).
- Achieved modulation factors >80% over a broad frequency band.
Conclusions:
- Surface passivation with Al2O3 drastically improves silicon photomodulator efficiency.
- The enhanced silicon modulators eliminate the need for bulky, expensive laser sources.
- Potential for compact, cost-effective modulators in imaging and signal processing, though limitations in switching speed and spatial resolution exist.
