Microconical silicon mid-IR concentrators: spectral, angular and polarization response.
Optics Express
|September 29, 2020
Summary
Researchers developed silicon microcone light concentrators to reduce thermal noise in infrared cameras. This innovation enhances photon collection, potentially increasing operating temperatures for focal plane arrays (FPAs).
Area of Science:
- Optics and Photonics
- Materials Science
- Semiconductor Devices
Background:
- Thermal noise in mid-wave and long-wave infrared (MWIR and LWIR) cameras and focal plane arrays (FPAs) is a significant challenge.
- Reducing photodetector area can decrease thermal noise but requires efficient photon collection.
- Light-concentrating structures offer a potential solution by enhancing photon capture on smaller detector areas.
Purpose of the Study:
- To investigate the use of microconical silicon (Si) light concentrators for reducing thermal noise in MWIR/LWIR FPAs.
- To explore methods for integrating Si microcones with FPAs to improve photon collection and operating temperatures.
- To analyze the performance of different microcone designs and integration strategies.
Main Methods:
- Numerical modeling in the mesoscale regime to design microconical Si light concentrators with (111) oriented sidewalls.
- Fabrication of microcones using anisotropic wet etching of Si (100) wafers.
- Study of three integration methods: inverted microcones with heterogeneous integration, inverted microcones with monolithic integration (Schottky barrier detectors), and regular microcones with monolithic integration.
Main Results:
- Inverted microcones with heterogeneous integration achieved resonant power enhancement factors (PEF) up to 10 and angles-of-view (AOV) up to 10°.
- Monolithic integration of inverted microcones with Schottky barrier photodetectors yielded resonant PEFs up to 25 and AOVs up to 30° for both polarizations.
- Regular microcones provided non-resonant power concentration with large AOVs, functioning similarly to optical components like dielectric microspheres.
Conclusions:
- Silicon microcone light concentrators are a viable solution for reducing thermal noise in infrared FPAs.
- Inverted microcone designs enable multispectral imaging with narrow bands (∼100 nm) and large AOVs.
- The proposed integration methods offer pathways to enhance FPA performance, including increased operating temperatures and improved imaging capabilities.
