The integration of quantum photonics devices in nanophotonic platforms is a promising approach for implementing scalable quantum systems for quantum sensing and communications applications. Superconducting nanowire single-photon detectors (SNSPDs) have developed into the most popular photon counting devices due to their high detection efficiency, low dark count rates, and time uncertainty (jitter). As many integrated structures, waveguide-coupled SNSPDs can benefit from the use of subwavelength gratings, which are periodic planar structures that enable the synthesis of metamaterials with tailorable optical properties, namely refractive index, wavelength dispersion, and anisotropy. In this work, we report on our latest advances regarding single-photon detection in silicon nitride waveguides, including the novel use of subwavelength grating metamaterials to enhance the performance of SNSPDs.