Abstract: A method for reducing speckle noise in a coherent imaging system includes applying a time varying phase gradient across a sample beam of the system to convert spatial distortion to temporal noise, recording a plurality of measurements of the sample beam, and averaging the plurality of measurements to reduce the temporal noise. Another method includes acquiring a plurality of sample scans while modulating a numerical aperture of a sample beam, and concatenating the plurality of scans such that speckle noise is decorrelated from adjacent scans of the plurality of scans. An apparatus for reducing speckle noise includes an optical element for applying a time varying phase gradient across a sample beam of the system to convert spatial distortion to temporal noise, a detector for recording a plurality of measurements of the sample beam, and circuitry for averaging the plurality of measurements to reduce the temporal noise.

Abstract: The invention features a waveguide based devices, methods, and systems to increase sensitivity of surface plasmon resonance (SPR) measurement through the use of differential detection. The enhanced sensitivity enables analysis and detection of a wide range of analytes including, for example, DNA, antibodies, proteins, and other chemical compounds. These methods achieve this result by sampling the SPR response curve at more than one point. This can be achieved using a detection device with sets of optical waveguides having distinct propagation parameters, or by using light of different wavelengths. These methods are suitable for multi-analyte and multi-sample applications in a miniaturized detection system. Furthermore, this invention makes use of an alternating polarity electric field to reduce nonspecific analyte binding and detection time.