Abstract: The present invention relates to the field of phase measurement, particularly optical phase measurement. In one form, the invention relates to a method and device for measuring the phase between distinct signals by converting phase variations between the signals into amplitude variations. In one embodiment the invention provides a method of arranging the structure of a two-dimensional or three-dimensional crystal to measure the phase between signals, comprising the steps of (i) providing a respective waveguide for each signal and (ii) providing a micro-cavity array arranged to provide a resonance output in response to the phase of the signals. The invention has application to a wide range of apparatus and devices across many industries including communications, food technology, pharmacology, medicine and biology.