Measurement-efficient optical wavemeters

We describe a method for efficiently determining the wavelength of a monochromatic source and provide an experimental proof-of-concept. The photomeasurement efficiency for a wavemeter can be written as η(N, q) = (1 + log_qN)/m, where N is the number of spectral channels, q is the number of distinguishable output levels per photodetector, and m is the actual number of photomeasurements made. An implementation is developed that achieves a theoretical efficiency of η(N, q) = 1. The proof-of-concept experiment achieves efficiencies η = O(1), where the deviation from theory is attributable to well-known optical effects and should be correctable in future versions.