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Scanning Polarizing Microscope

IP.com Disclosure Number: IPCOM000038850D
Original Publication Date: 1987-Mar-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 2 page(s) / 37K

Publishing Venue

IBM

Related People

Wickramasinghe, HK: AUTHOR [+2]

Abstract

The measurement of phase difference between horizontal and vertical polarizations of a laser beam both before and after interacting with a specimen in a polarization microscope permits significant improvement in detection sensitivity. The heterodyne detection system is shown in the schematic illustration. Light from a Zeeman split, frequency stabilized, single-mode laser 1 provides right and left circular polarizations at frequencies of wo + wm and wo- wm, respectively, where wo is the optical frequency and wm is determined by the axial magnetic field applied to the laser. A half-wave plate on the laser converts the circular polarizations to horizontal and vertical polarizations. Output light passes through Bragg cell 2 that upshifts the light frequency and blocks reflected light.

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Scanning Polarizing Microscope

The measurement of phase difference between horizontal and vertical polarizations of a laser beam both before and after interacting with a specimen in a polarization microscope permits significant improvement in detection sensitivity. The heterodyne detection system is shown in the schematic illustration. Light from a Zeeman split, frequency stabilized, single-mode laser 1 provides right and left circular polarizations at frequencies of wo + wm and wo- wm, respectively, where wo is the optical frequency and wm is determined by the axial magnetic field applied to the laser. A half-wave plate on the laser converts the circular polarizations to horizontal and vertical polarizations. Output light passes through Bragg cell 2 that upshifts the light frequency and blocks reflected light. The first- order beam encounters beam-splitter 3 and part of the beam is reflected to polarizer 4 oriented at 45o to the horizontal. The resulting two beam components interfere at photodiode 5 to provide a reference signal at 2 wm that passes through limiter 6, becoming insensitive to amplitude fluctuations. The remainder of the laser beam that passes through beam-splitter 3 is focused by lens 7 on specimen 8, and is partially reflected. Reflected light is diverted by beam-splitter 3 through polarizer 9 at 45o to the horizontal onto photodiode 10 with the resulting signal to limiter 11. This produces another signal at 2 wm whose phase differs from that of...