NSLS-II Seminar

Phase retrieval is a method of determining the phase of an optical field employing only simple measurements of the near-focus intensity patterns produced by the field. Phase retrieval is distinguished by the simplicity of the experimental arrangements required and the flexibility of the method. The simplicity of the apparatus allows for its use in wavelength regimes where more complex arrangements are not possible. It is also capable of measuring non-spherical surfaces and wavefronts without a null optic or retrace and imaging errors. We will describe and contrast the two different classes of algorithm, known as Iterative Transform Algorithms and Nonlinear Optimization Algorithms. We then describe the simulation and experimental results measuring optical surfaces and wavefronts using a Nonlinear Optimization algorithm, demonstrating that the method is capable of measurements with accuracies on the order of a thousandth of a wavelength RMS. We also will discuss the practical limitations of the method and approaches to mitigate these.