Various embodiments of the present invention are directed to analyte detection methods and to photonic-based sensors that employ photonic crystal gratings to detect analytes. In one embodiment of the present invention, a photonic-based sensor includes a source, a photonic crystal, and a photodetector. The source is configured to output electromagnetic radiation. The photonic crystal includes a photonic crystal grating positioned to receive the electromagnetic radiation. The electromagnetic radiation interacts with the photonic crystal grating and an analyte situated on or in the photonic crystal grating to produce a transmission spectrum that characterizes the analyte. The photodetector is positioned to detect the transmission spectrum.