Sensitive detection of phase and absorption gratings: Phase-modulated, homodyne detected holography

Abstract

Phase-modulated holography (PMH) is a new technique for detecting very weak changes of the absorptivity or of the refractive index that occur in the course of an irreversible solid-state photoreaction. In contrast to conventional, phase-insensitive holographic techniques and to previous homodyne-detected holography, PMH allows to record the absorptive and dispersive hologram diffraction amplitudes separately and simultaneously, including their correct signs. PMH typically offers an up to eight orders of magnitude improvement of detection sensitivity over conventional techniques. These features render PMH an ideal tool for investigating new holographic recording materials, both for details of the underlying photoreaction and for the hologram formation mechanism.