Coherence spectroscopy by the Nth power of the measured signal in an interferometer overcoming the diffraction limit

Coherence spectroscopy has been intensively studied over the last several decades for various applications in science and engineering. The Rayleigh criterion defines the resolution limit of an interferometer, where many-wave interference beats the resolution limit of a two-slit system. On the other hand, the diffraction angle in a slit is reduced by the Kth power of the measured signal, resulting in the shot-noise limit. Here, the Kth power of the measured signal in an N-slit interferometer is studied for enhanced coherence spectroscopy to overcome the resolution limit of the original system. The Kth power to the individual intensities of the N-slit interferometer is numerically demonstrated for enhanced resolution satisfying the shot-noise limit. As a result, the Kth power of the intensity beats the resolution limit of the N-slit interferometer, in which the out-of-shelf spectrometer or wavelength meter can be a primary beneficiary of this technique. Due to the same resolution of the Heisenberg limit in quantum sensing as in the N-slit interference fringe, the proposed Kth power technique also beats the superresolution in quantum metrology.