Ultrasensitive nonlinear phase metrology

We present an ultrasensitive phase measurement system using time-holographic recording with a Mach-Zehnder interferometer (MZI). Operating the MZI near destructive interference and introducing small optical path variations via a phase modulator exploits the nonlinear relationship between signal and output phases. The output phase is extracted by interfering with a slightly detuned reference beam, producing a temporally modulated hologram encoding amplitude and phase information. Digital reconstruction of the amplified signal phase, with demonstrated amplification factors tunable to thousands is enabled. The system achieves phase sensitivities better than λ/1000, allowing sub-nanometer precision. Replacing the MZI with a photorefractive two-wave mixing system extends its capabilities to transient phase detection with exceptional sensitivity. This adaptable system offers a powerful tool for ultrasensitive phase measurements in scientific and technological applications.