**5. Conclusions**

In this study, we present a method for the elimination of unwanted modes in a wavelength-selective uncooled IR sensor, using a subtraction operation with a reference pixel. To this end, MEMS-based wavelength-selective uncooled IR sensors using 2D PC-PMAs with reference pixels were fabricated using CMOS and micromachining techniques. The reference pixel possessed the same sensor structure, except a flat mirror was used on the absorber surface instead of PMAs. The spectral responsivity measurements demonstrated that single-mode detection was achieved through the subtraction operation with a reference pixel. It is important to consider the absorptions in other regimes by the PC-PMA-based uncooled IR sensors from an application standpoint. The concept demonstrated in this study can be applied to any type of uncooled IR sensor, such as bolometers [35], silicon-on-insulator diodes [36,37], ferroelectrics [38], and photomechanical sensors [39,40] with wavelength- or polarization-selective absorbers that are capable of multispectral or polarimetric detection, and also to any type of PMAs such as PC, MIM, mushroom, and other types of structures.

**Author Contributions:** S.O. conceived and designed the experiments and theoretical investigations; Y.T. fabricated the sensors and performed measurements; M.K. supervised all aspects of the research; all authors discussed the results and contributed to writing the manuscript.

**Funding:** This research received no external funding.

**Conflicts of Interest:** The authors declare no conflict of interests.
