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Updated: Jun 23, 2026
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Wavelength-Tunable, Low-Angular Dispersion, and Narrowband Thermal Emitters by Incorporating Ge2Sb2Te5 Layer into
Yuan-Wei Chang1, Po-Wei Ho2, Hui-Hsin Hsiao1,3
1Department of Engineering Science and Ocean Engineering, National Taiwan University, Taipei 10617, Taiwan.
ACS Applied Materials & Interfaces
|June 22, 2026
Summary
A novel tunable mid-infrared (MIR) light source using a Ge2Sb2Te5 layer achieves high Q-factors and low angular dispersion. This breakthrough enhances molecular fingerprint discrimination for sensing applications.
Area of Science:
- Photonics and Plasmonics
- Materials Science
- Infrared Spectroscopy
Background:
- High-quality-factor (Q-factor) mid-infrared (MIR) light sources are crucial for sensing.
- Existing metal-dielectric-metal (MDM) structures suffer from ohmic loss and angular dependence.
- Need for tunable, narrowband, and angularly stable MIR emitters.
Purpose of the Study:
- To develop a continuously tunable, low-angular dispersion, narrowband thermal emitter in the MIR.
- To investigate the performance of a Ge2Sb2Te5 (GST) layer integrated into a grating-assisted distributed Bragg reflector (DBR)-like structure.
- To demonstrate enhanced Q-factors and reduced ohmic loss compared to conventional structures.
Main Methods:
- Incorporation of a GST layer into a grating-assisted DBR-like structure, avoiding direct contact with a metallic back reflector.
- Simulation of hybridized localized surface plasmon (h-LSP) modes under transverse-magnetic (TM)-polarized light.
- Fabrication of samples with varying grating widths and thermal annealing for tunability.
Main Results:
- A hybridized localized surface plasmon (h-LSP) mode with a simulated Q-factor of 30.64 was achieved, significantly higher than LSP modes in MDM structures (Q-factor of 6.17).
- The h-LSP mode exhibited negligible wavelength variation with changing incidence angles.
- Thermal annealing of fabricated samples resulted in a continuous redshift of emission spectra (average 140 nm) with sustained high Q-factors (above 8.70).
- The observed redshift correlated with the crystalline fraction of the GST layer.
Conclusions:
- The developed GST-integrated grating structure provides a continuously tunable, narrowband, and angularly stable MIR light source.
- This technology offers a promising pathway for improving the accuracy of molecular fingerprint discrimination in sensing applications.
- The reduction in ohmic loss and enhanced Q-factors highlight the potential of this novel design.
