US Patent 7508523 Interferometric system for complex image extraction

The invention provides an interferometric system and method for quadrature detection of optical characteristics of a sample. The system includes a Mach-Zehnder interferometer providing a variable optical delay between light collected from the sample and reference light. The Mach-Zehnder interferometer has an output M×N coupler with N≧3 output ports. Two differential detectors, each having two input ports coupled to a different two of the N output ports of the M×N coupler, produce first and second electrical signals having an interferometric phase shift. A processor is provided for computing real and imaginary parts of a complex refractive index of the sample from the first and second electrical signals by using complex deconvolution.