A simple heterodyne interferometer associates with phase to amplitude conversion and amplitude sensitive technique is
proposed. The excess noise and the quantum noise introduced by the autocorrelations between sensing beam and local
oscillator beam are reduced at suitable phase bias. Meanwhile, the differential phase arises from target displacement is
detected by optical differential and optical additive operations. The amplitude and phase quadrature are also achieved
simultaneously in proposed interferometer.
The high precision measurement of displacement in nanoscale is crucial to nowadays many applications. We present a heterodyne interferoemtry with external modulation configuration for nanoscale displacement measurement. In the proposed method, the differential phase introduced by the displacement is converted into the amplitudes of quadrature heterodyne signals, so that the displacement can be determined from the amplitude ratio of the quadrature signals. The phase to amplitude conversion is achieved through the optical addition and subtraction by polarization tuning, which results in two phase quadrature signals in amplitude quadrature. Therefore, the proposed method also benefits from the feature of differential detection with common noise rejection. The nonlinearity of measurement due to polarization coupling is reduced by the conversion and the frequency coupling is eliminated by the external modulation approach. With proper phase bias to keep the interferometer in dark fringe operation, the shot-noise-limited performance is possible to realize. To demonstrate the capability of proposed method in real-time displacement measurement, we measure the dynamics of a commercially available PZT pusher and found close agreement between the experiment and the theory. The experimental evidence is also found with spectral distribution measurements, which demonstrates the minimum detectable phase and noise suppression capability of this approach.
A simple interferometric scheme is presented to characterize the 2-D distribution of linear birefringence with full-range capability. Since the interference images are obtained with respect to different orientations of a linearly polarized incident laser beam, the measurement speed can be improved once the orientation adjustment is achieved electronically. In addition, the measurement is independent of a nonuniform distribution of laser intensity, which is demonstrated experimentally and briefly explained theoretically. Furthermore, the measurement of residual linear birefringence distribution is also demonstrated successfully and verified by error analysis.
In this investigation, an interferometric scheme is developed to determine the linear birefringent parameters of wave plate in full range. A commercially available Soliel Babinet compensator and a half wave plate are taken as sample to demonstrate the capability of two-dimensional measurement. Since images are obtained with respect to different polarization orientations of a linearly polarized incident laser beam, the measurement speed can be improved once the polarization orientation adjustment is achieved electronically. The measurement is also independent of non-uniform distribution of laser intensity, this is demonstrated experimentally and briefly explained theoretically. In addition, the 2-D distribution of residual linear birefringent parameters is also demonstrated.