Systems, apparatuses, and methods for detecting carious lesions are described herein. In an example, the systems in an optical interrogator including a single-pixel photodetector responsive to short-wave infrared light and operatively coupled to a controller. In an example the optical interrogator includes a light engine for emitting light, a scanning mirror assembly and a single-pixel photodetector. In an example, the methods include causing the light engine to emit light having wavelengths in a range of about 900 nm to about 1,700 nm; selectively directing the light over different portions of a tooth with a scanning mirror assembly to provide scattered light; and correlating scattered light signals generated by the single-pixel photodetector in response to the scattered light with the portion of the tooth.