Programmable spectral interferometric microscopy

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Riza, Nabeel A.
Bakker, Maarten
Bokhari, Amana
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A programmable optical sensor is proposed based on spectrally programmable heterodyne optical interferometric confocal microscopy implemented via an ultrastable in-line acousto-optic tunable filter (AOTF) based interferometer using double anisotropic acousto-optic Bragg diffraction. The design uses a tunable laser as the light source and anisotropic diffractions in an AOTF to generate two near-collinear orthogonal linear polarization and slightly displaced beams that both pass via the test sample to deliver highly sensitive sample birefringence or material optical retardation measurements. A spherical lens is used to form focused spots for high resolution confocal spatial sampling of the test object. Thus the instrument also forms a classic interferometric confocal microscope via the use of single mode fiber optics for the receive light. The laser and AOTF tuning allows birefringence measurements taken at different wavelengths, one at a time with minimal interwavelength crosstalk. Experimental demonstration of the instrument is achieved using a 1550nm center 100nm band tunable laser and variable birefringence liquid crystal and fixed retardance birefringent materials, all showing accurate retardation measurements to within a 0.5° rf phase accuracy. The instrument shows a fiber-in to fiber-out loss of 8.5dB. An alternate design via a transmissive beam generation design provides collinear co-located beams on the sample plane for superaccurate measurements.
Microscopic examination , Acoustooptical effects , Birefringence , Crosstalk , Electromagnetic wave diffraction , Heterodyning , Interferometry , Lenses , Optical filters , Interferometric microscopy , Interwavelength crosstalk , Spherical lenses , Tunable lasers
Riza, N. A.; Bakker, M. and Bokhari, A. (2005) 'Programmable spectral interferometric microscopy', Review of Scientific Instruments, 76, 033107 (10 pp). doi: 10.1063/1.1866832
© 2005 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. The following article appeared in Rev. Sci. Instrum. 76, 033107 (2005), and may be found at