Making a commercial infrared pyroelectric detector sensitive to millimetre waves via near-field metasurface-pyroelectric film interaction

Unlike neighbouring spectral regions, millimetre and submillimetre waves (i.e., Terahertz frequencies) have been proven to be difficult to generate and detect [1]. With the advent of metamaterials and metasurfaces, new venues to optimize emitters and detectors for such challenging radiation have been opened. We propose here a simple approach to turn an economical commercial infrared pyroelectric detector into a 140 GHz polarization-dependent detector [2]. The scheme relies on the introduction of a deep-subwavelength thin absorber on top of the pyroelectric film. The small separation compared with the resonance wavelength between the absorber’s top metasurface and the ground plane as well as the direct contact of the ground plane with the pyroelectric detector top electrode triggers strong nearfield interactions that make it possible the absorption of millimetre wave radiation by the few-μm thick pyroelectric film that otherwise would be transparent. We first optimize and fabricate the absorber (λ-to-thickness ratio of ~140) based on an array of rectangular metal patches on a grounded propylene slab as an individual entity to test its performance (solid black line in Fig. 1). Afterwards, we integrate the absorber into the infrared pyroelectric detector, housing the resulting structure in an Ar-filled KT-3 package with the original germanium window substituted for a 350 μm thick sapphire slab to provide transparency for the incoming 140 GHz radiation. The voltage responsivity and time response of the final prototypes show performances for millimetre wave radiation similar to the original detector for infrared radiation. The proposed detectors can be easily integrated into one- or two-dimensional arrays to enable spectral and polarization analysis of (sub)millimetre wave beams without using supplementary dispersive elements.

[1] G. Carpintero, E. García-Muñoz, H. Hartnagel, S. Preu, and A. Raisanen, Semiconductor TeraHertz Technology: Devices and Systems at Room Temperature Operation (Wiley-IEEE Press, 2015).
[2] S.A. Kuznetsov, A.G. Paulish, M. Navarro-Cía, and A. V. Arzhannikov, Sci. Rep. 6, 21079 (2016)