Laser scanning interferometric surface metrology

A quadrature interferometric method for determining the presence or absence of a target analyte in a sample, comprising:

• generating a single incident beam having a wavelength λ and a waist wo to probe at least a portion of a substrate having a reflecting surface that has been exposed to the sample, the reflecting surface including at least a first region having a layer of recognition molecules specific to the target analyte and a second region that does not include a layer of recognition molecules specific to the target analyte;
• scanning the first region and the second region with the single incident beam while the substrate is maintained in a substantially fixed position, the single incident beam being reflected to generate a single self-referencing diffracted beam that includes signal and reference components;
• and
• measuring a time dependent intensity of the single self-referencing diffracted beam.

A method for a high rate of inspection of a surface of a target using laser scanning quadrature interferometric detection, comprising:

• generating a single probe laser beam having a wavelength λ;
• passing the single probe laser beam through an acousto-optic modulator for angular deflection of the probe laser beam and then passing the deflected beam through a lens having a focal length f to focus the probe laser beam to a single incident beam having a waist wo on the surface of the target, wherein the surface of the target is adapted to reflect the single incident beam therefrom as a single self-referencing diffracted beam, the single self-referencing diffracted beam including signal and reference components;
• and
• measuring a time dependent intensity in a substantially quadrature condition of the reflected single self-referencing diffracted beam, the scanning occurring via controlling the angular deflection caused by the acousto-optic modulator.

An apparatus for assessing topology of a surface of a target, comprising:

• an optical source for generating a probe laser beam;
• means for scanning the probe laser beam across at least a portion of the surface of the target, the means for scanning including an acousto-optic modulator;
• a lens with a focal length f for focusing the probe laser beam with a waist w0 on the surface of the target, the lens being positioned between the means for scanning and the target;
• and
• a beamsplitter positioned to redirect a self-referencing return signal toward a means for detecting the return signal in a substantially quadrature condition, the return signal resulting from reflection of the probe laser beam off the surface of the target, wherein the means for detecting the return signal includes an adaptive optic element used in conjunction with two separate photodetectors.

A method for a high rate of inspection of a surface of a target using laser scanning quadrature interferometric detection, comprising:

• generating a probe laser beam having a wavelength λ;
• passing the probe beam through an acousto-optic modulator for angular deflection of the probe beam and then passing the deflected beam through a lens having a focal length f to focus the probe beam to a waist wo on the surface of the target;
• and
• measuring a time dependent intensity in a substantially quadrature condition of a reflected diffraction signal resulting from scanning the probe beam across at least a portion of the surface of the target, the scanning occurring via controlling the angular deflection caused by the acousto-optic modulator, wherein the quadrature condition is maintained using an adaptive optic element.