Wavelength- or Polarization-Selective Thermal Infrared Detectors for Multi-Color or Polarimetric Imaging Using Plasmonics and Metamaterials

Abstract

Wavelength- or polarization-selective thermal infrared (IR) detectors are promising for various novel applications such as fire detection, gas analysis, multi-color imaging, multi-channel detectors, recognition of artificial objects in a natural environment, and facial recognition. However, these functions require additional filters or polarizers, which leads to high cost and technical difficulties related to integration of many different pixels in an array format. Plasmonic metamaterial absorbers (PMAs) can impart wavelength or polarization selectivity to conventional thermal IR detectors simply by controlling the surface geometry of the absorbers to produce surface plasmon resonances at designed wavelengths or polarizations. This enables integration of many different pixels in an array format without any filters or polarizers. We review our recent advances in wavelength- and polarization-selective thermal IR sensors using PMAs for multi-color or polarimetric imaging. The absorption mechanism defined by the surface structures is discussed for three types of PMAs-periodic crystals, metal-insulator-metal and mushroom-type PMAs-to demonstrate appropriate applications. Our wavelength- or polarization-selective uncooled IR sensors using various PMAs and multi-color image sensors are then described. Finally, high-performance mushroom-type PMAs are investigated. These advanced functional thermal IR detectors with wavelength or polarization selectivity will provide great benefits for a wide range of applications.

Keywords: absorber; infrared detector; metamaterials; plasmonics; polarization; thermal infrared; uncooled; wavelength-selective.

Figure 1

Operation principle of thermal IR detectors.

Figure 2

Schematic illustrations of the oblique and cross-sectional views of three types of PMAs: (a,d) Crystal-type; (b,e) MIM-type and (c,f) MR-type structures.

Figure 3

Concept of pixel integration in an array format for (a) multi-color; and (b) polarimetric imaging using PMAs.

Figure 4

(a) Schematic diagram of the uncooled IR sensor (thermopile) with Au-based 2D-PA; (b) SEM image of the microelectromechanical systems (MEMS)-based thermopile with 2D-PA. Magnified SEM images of the 2D-PAs of (c) (ii) and (d) (vii); (e) Schematic diagram of the 2D-PA.

Figure 5

Measured spectral responsivity of developed sensors (a) (ii) and (vii); and (b) (i) to (viii); (c) Peak wavelength of the responsivity as a function of surface period for 2D-PA with square lattice; (d) Comparison of peak responsivity vs. surface period for 2D-PA square and triangular lattices.

Figure 6

(a) Schematic of TH MIM-PMAs; (b) Measured reflectance of MIM-PMAs with various micropatch sizes; (c) Pixel structure of SOI diode uncooled IRFPA with TH MIM-PMAs.

Figure 7

(a) Optical microscopy image of the developed image sensor with two TH MIM-PMAs. SEM images of MIM-PMAs integrated in the (b) left and (c) right halves of the pixel array; (d) Optical image of the light emitter used in the image; (e) Image of the light emitter obtained using the developed image sensor with the narrow bandpass filter centered at 4.7 μm.

Figure 8

Schematic and SEM images of the uncooled IR sensor (thermopile) using (a,c) Au-based 2D-PA with ellipsoidal dimples; and (b,d) 1D-PA. The definition of the electric field polarization angle (θ) was defined according to the axis of the ellipsoid and the gratings.

Figure 9

Measured polarization dependence of spectral responsivity of developed uncooled IR sensors using 2D-PAs with (a) circular and (b) ellipsoidal dimples, and with (c) 1D-PAs. (d) Relationship between the extinction ratio and the ellipticity.

Figure 10

Schematic and cross-sectional images of MR-PMAs with (a,c) cylindrical and (b,d) tubular posts.

Figure 11

Calculated absorbance spectra of MR-PMAs with cylindrical posts. (a) Spectra for various w_m and (b) as a function of wavelength and w_m. Calculated absorbance of MR-PMAs with tubular posts; (c) Spectra for various w_m and (d) as a function of wavelength and w_h. The color map defines the absorbance scale.

Figure 12

SEM images of MR-PMAs with tubular posts: (a) top; (b) oblique; and (c) magnified cross-sectional views of the periodic structures.

Figure 13

Experimental reflectance spectra for devices with w_m and w_h of (a) 3.5 and 1.5 µm; and (b) 4.3 and 0.7 µm.