An apparatus comprises a slider having an air-bearing surface (ABS), a write pole at or near the ABS, and a reader at or near the ABS and connected to a pair of reader bond pads of the slider. A near-field transducer (NFT) is formed on the slider at or near the ABS, and an optical waveguide is formed in the slider and configured to receive light from a laser source. A sensor is situated proximal of the write pole at a location within the slider that receives at least some of the light communicated along the waveguide. The sensor may be electrically coupled to the reader bond pads in parallel with the reader, and configured to generate a signal indicative of output optical power of the laser source.