An approach for characterizing an optical near field transducer (NFT) involves providing excitation radiation to the NFT. The NFT emits photoluminescent radiation in response to the excitation radiation. The output radiation from the NFT is filtered so that a portion of the photoluminescent radiation emitted by the NFT passes through the filter and the excitation radiation is substantially blocked. A detector detects the portion of photoluminescent radiation and outputs an electrical signal in response to detection of the portion of photoluminescent radiation.