This paper presents the measurement and analysis method for detection of the mm-wave signal at 96 GHz, by using a low-cost microbolometer infrared (IR) camera with 70 μm pixel-pitch optimized for detection in the 8-12 μm (LWIR) range. The mm-wave beam derived from a multiplied Schottky diode based source is detected within ~ 65 % of the whole area of a 160×120 pixel focal plane array microbolometer sensor. Under ~73 mW incident power, responsivity is measured as 7.3 V/W, and the average noise for the measurement is determined as 12 μV, which includes both detector and readout electronics contribution. From the measured parameters, the integrated Noise Equivalent Power (NEP) is calculated as 1.63 μW within the 7.8 kHz readout bandwidth. By using a simple setup, it is shown that a low-cost microbolometer camera which is designed for LWIR range can detect a distinct mm-wave beam at 96 GHz.
This paper introduces a method for a broadband absorption enhancement in the LWIR range (8-12 μm), in single layer microbolometer pixels with 35 μm pitch. For the first time in the literature, this study introduces a very simple and low cost approach to enhance the absorption by embedding plasmonic structures at the same level as the already existing metallic layer of a microbolometer pixel. The metal layer comprises the electrode and the arm structures on the body. Even though the periodicity of the plasmonic structures is slightly disturbed by the placement of the electrodes and the connecting metal, the metal arms and the electrodes compensate for the lack of the periodicity contributing to the resonance by their coupling with the individual plasmonic resonators. Various plasmonic structures are designed with FDTD simulations. Individual, plasmonically modified microbolometer pixels are fabricated, and an increase in the average absorption due to surface plasmon excitation at Au/Si3N4 interfaces is observed. Plasmonic structures increase the average absorption from 78% to 82% and result in an overall enhancement of 5.1%. A good agreement between the simulation and the FTIR measurement results are obtained within the LWIR range. This work paves the way for integration of the plasmonic structures within conventional microbolometer devices for performance enhancement without introducing additional costs.