US 6,188,477 B1 · Optical polarization sensing apparatus and method

Abstract

An integrated polarization sensing apparatus and method uses a self-homodyne detection scheme to provide required sensitivity for numerous applications, such as glucose concentration monitoring, without the need for expensive, bulky components. The detection scheme is implemented by splitting a polarized laser beam with a polarization beam splitter into a P wave component and an S wave component, phase modulating the P wave component and recombining the two components. The polarization of the combined optical beam is then rotated slightly by the variable to be monitored, such as by passing the beam through a glucose solution. Finally, the beam is passed onto a photodetector that generates a signal that is proportional to the polarization rotation angle. This device has the advantage of employing optical components, including polarizing beam splitters, phase modulators and lenses, that can all be fabricated on a single silicon chip using MEMS technology so that the device can be made compact and inexpensive.

Claims20

Dependent claims

Apparatus for sensing polarization rotation of an optical beam comprising:

a) an optical beam source for generating a first optical beam of a first known frequency;
b) a polarization beamsplitter for receiving said first optical beam and forming first and second component beams, a first of which is a transmitted beam having a first polarization sense and a second of which is a reflected beam having a second polarization sense that is perpendicular to said first polarization sense;
c) a phase modulator for phase modulating one of said first and second component beams and thereby generating a phase modulated beam, said phase modulator operating at a second known frequency that is lower than said first known frequency;
d) a beamsplitter for combining said phase modulated beam with the other of said first and second component beams, and thereby forming a combined optical beam;
and
e) a photodetector for receiving said combined optical beam and generating a photocurrent that is related to a polarization rotation angle that is imparted to either said first optical beam or said combined optical beam.

3 more elements

Dependencies are inferred from the claim text.

Optical polarization sensing apparatus and method

Life of this patent

Optical polarization sensing apparatus and method

Life of this patent

Abstract

Claims20