Wavelength-selective multispectral and hyperspectral imaging systems in the visible and near-infrared (NIR) range have shown immense potential in applications such as remote sensing, biomedical diagnostics, and optical communications. In this thesis, we present a series of advances in narrowband filter design, SPAD-based imaging integration, and metasurface-enabled polarimetric systems.

First, we demonstrate a 16-band ultra-narrow hyperspectral imaging system based on a Fabry-Perot (FP) structure, operating across the 715-915 nm NIR range. The filter consists of two SiC/SiO2 distributed Bragg reflectors (DBRs) separated by a tunable SiO2 spacer. Using the transfer matrix method, we optimize the design to achieve high transmittance and sharp spectral resolution, with a measured full-width-at-half-maximum bandwidth of 5-10 nm. We further integrate this FP filter with a single-photon avalanche diode (SPAD) sensor, SwissSPAD2, to enable photon-level hyperspectral measurements. A novel spectral classification method based on a nearest-node algorithm is proposed to mitigate crosstalk between overlapping bands, allowing accurate reconstruction of spectral content. This integration paves the way to compact and high-resolution imaging applications, such as snapshot hyperspectral SPADs and fluorescence lifetime imaging microscopy (FLIM).

Second, we introduce a planar, 16-band wavelength-selective filter that combines DBRs with a sub-wavelength grating metasurface embedded in the cavity. By tailoring the grating geometry, we achieve tunable spectral responses in a fabrication-friendly, fully planar structure. Effective medium theory facilitates efficient simulation and design, reducing dimensional complexity. The structure also exhibits polarization sensitivity, which can be exploited for precise polarization detection of incident light. This enables applications in bio-imaging, LiDAR, and polarization-resolved sensing.

Lastly, we present the design and fabrication of 450 nm tall TiO2 metasurfaces operating at 520 nm, tailored for use with SPAD-based polarimetry. These metasurfaces function as linear polarizers, quarter-wave plates, and phase retarders, achieving precise polarization control with sub-wavelength thickness. Using a Mueller Matrix characterization setup, we evaluate their optical performance and demonstrated excellent agreement with ideal polarization components, as well as remarkable fabrication stability and repeatability. Furthermore, we replicate the multifunctional behavior described by Rubin et al., thus achieving simultaneous polarization manipulation and diffraction, thereby validating the metasurface multifunctionality. Looking ahead, we propose a co-design approach to further enhance polarization control, enabling integration with SPAD arrays for massively parallel, polarization-sensitive imaging. To support scalability, nano-imprint lithography offers a promising path toward mass production, bringing metasurface-enabled optical systems closer to practical applications in FLIM, direct time-of-flight sensing, quantum technologies, and beyond.

Together, these advances highlight the synergy between flat optics, SPADs, and metasurfaces, and lay the groundwork for highly integrated, multi-functional imaging systems capable of capturing spatial, spectral, temporal, and polarization information with high fidelity.