Sanjib Chatterjee

Bio: Sanjib Chatterjee is an academic researcher from Raja Ramanna Centre for Advanced Technology. The author has contributed to research in topics: Interferometry & Wavefront. The author has an hindex of 9, co-authored 46 publications receiving 262 citations. Previous affiliations of Sanjib Chatterjee include Indian Department of Atomic Energy.

Simple technique for the generation of plane surface normal to optic axis direction of uniaxial crystal

Abstract: What we believe to be a new experimental technique for the generation of a plane crystal surface perpendicular to the optic axis direction of a transparent birefringent uniaxial crystal is presented. A simple setup has been described for the initial optic axis alignment of a raw uniaxial crystal blank. Error correction methods have been illustrated. A technique for producing high optical quality surfaces by block polishing plane parallel crystal surfaces normal to the direction of the optic axis, in one setting, is discussed. The block with angular graduations facilitates the correction of angular error. A new conoscopy setup has been coupled to a Fizeau interferometer for high accuracy testing of the optic axis alignment with respect to the surface normal of the relevant polished surface of the uniaxial crystal. The results obtained for a quartz crystal blank are presented.

Determination of Refractive Index In-Homogeneity of Transparent, Isotropic Optical Materials

Abstract: Interferometric methods for the measurement of refractive index inhomogeneity of transparent, isotropic optical materials such as optical glass, fused silica, laser glass etc. have been discussed.

Measurement of the surface form error of a spherical surface with a wedge phase shifting Fizeau interferometer

Abstract: A new technique for the measurement of surface form error of a test spherical surface with respect to a reference spherical surface, using wedge phase shifting Fizeau interferometer, is presented. A two stage measurement method is discussed. The individual surface form error of the test and reference spherical surfaces along with the residual wave front aberration introduced by the common optical elements in the Fizeau cavity are measured with respect to a plane reference surface using phase shifting interferometry. Finally, data subtraction is used to eliminate the effect of the residual wave front aberration introduced by common optical elements and thereby transforming the result as the surface form error of the test spherical surface with respect to the reference spherical surface. Results obtained for a test spherical surface is presented.

Opaque optics thickness measurement using a cyclic path optical configuration setup and polarization phase shifting interferometry

Abstract: Thickness measurement of an opaque optics using a cyclic path optical configuration (CPOC) setup and polarization phase shifting interferometry (PPSI) is presented. The CPOC setup is used to simultaneously focus two orthogonally polarized counterpropagating converging beams at its hypotenuse arm. The opaque optics is placed at the hypotenuse arm of the CPOC setup such that one of its surfaces reflects back one of the counterpropagating focusing beams. Because of the thickness of the opaque optics, the other focusing beam suffers a longitudinal shift in the beam focus. Applying PPSI, the longitudinal shift in the beam focus which is twice the thickness of the opaque optics is determined. The results obtained for a silicon plate of thickness 0.660 mm with a measurement uncertainty of 0.013 mm are presented.

Determination of the index inhomogeneity of transparent isotropic optical material with a dual Sagnac interferometer.

Abstract: A technique for the measurement of inhomogeneity of optical glass, fused silica, etc., using a Sagnac interferometer (SI) has been presented. An SI produces a pair of laterally separated, mutually parallel, collimated beams with orthogonal planes of polarization, i.e., p and s polarizations from an expanded, linearly polarized (45°) collimated He-Ne (632.8 nm) input laser beam. The p and s beams pass through a liquid-filled cell with plane parallel glass windows. The test glass with plane parallel end surfaces is kept in the path of the p beam in the index matching liquid, while the s beam traverses a parallel path through the liquid. Another SI recombines the emergent p and s beams by removing the lateral shear. A quarter-wave plate transforms the state of polarization of the beams to opposite circular polarizations of which the components selected by a linear polarizer interfere to form Fizeau fringes. Polarization phase shifting interferometery has been applied to determine the optical path difference (OPD) variations. The OPD variation without the test glass is subtracted from that with test glass to eliminate the effect of system aberration. The results for a phosphate laser glass sample have been presented.

Young`s interference experiment with light scattered from two atoms

Abstract: We report the first observation of interference in the light scattered from two trapped atoms ({sup 198}Hg{sup +} ions localized in a linear Paul trap). The visibility of the interference fringes can be explained in the frame-work of Bragg scattering by a harmonic crystal, but with important differences compared to the case of a large crystal. Comparison of the experimental data with theory shows that the interference pattern offers another method to determine ion temperatures and separations. Furthermore, by exploiting the atom`s internal structure we have found a way to obtain {open_quotes}which path{close_quotes} information without invoking the position-momentum uncertainty relation. If the light scattered by the atoms is detected in a polarization-sensitive way, then it is possible to selectively demonstrate either the particle-nature or the wave-nature of the scattered photons.

Characterization of Bessel beams generated by polymeric microaxicons

Abstract: We present a quick, simple and accurate digital holographic characterization of the Bessel beams produced by polymeric microaxicons. This technique allows the numerical reconstruction of both intensity and phase of the beam at whichever point starting from a single acquired hologram. From these data, it is possible to go back to the axicon structure, and to gather information about their characteristics. In particular, the focal length and the depth of focus of the axicon lens are experimentally measured, and the full width at half maximum of the beam is obtained too. The depth of focus, very large for a Bessel beam with respect to a Gaussian one, is successfully exploited for optical trapping of micrometric objects.

Laser differential reflection-confocal focal-length measurement

Abstract: A new laser differential reflection-confocal focal-length measurement (DRCFM) method is proposed for the high-accuracy measurement of the lens focal length. DRCFM uses weak light reflected from the lens last surface to determine the vertex position of this surface. Differential confocal technology is then used to identify precisely the lens focus and vertex of the lens last surface, thereby enabling the precise measurement of the lens focal length. Compared with existing measurement methods, DRCFM has high accuracy and strong anti-interference capability. Theoretical analyses and experimental results indicate that the DRCFM relative measurement error is less than 10 ppm.

Development of a compact, fiber-coupled, six degree-of-freedom measurement system for precision linear stage metrology

Abstract: A compact, fiber-coupled, six degree-of-freedom measurement system which enables fast, accurate calibration, and error mapping of precision linear stages is presented. The novel design has the advantages of simplicity, compactness, and relatively low cost. This proposed sensor can simultaneously measure displacement, two straightness errors, and changes in pitch, yaw, and roll using a single optical beam traveling between the measurement system and a small target. The optical configuration of the system and the working principle for all degrees-of-freedom are presented along with the influence and compensation of crosstalk motions in roll and straightness measurements. Several comparison experiments are conducted to investigate the feasibility and performance of the proposed system in each degree-of-freedom independently. Comparison experiments to a commercial interferometer demonstrate error standard deviations of 0.33 μm in straightness, 0.14 μrad in pitch, 0.44 μradin yaw, and 45.8 μrad in roll.

A ring-shaped random laser in momentum space.

Abstract: A ring-shaped random laser in momentum space is designed by directly coupling a random laser with a commercial optical fiber. By using a simple approach of selectively coating the random gain layer on the surface of the fiber, red and yellow random lasers are respectively achieved with low threshold values and a good emission direction due to the guiding role of optical fibers. The unique coupling mechanism leads to a random laser with a ring shape in momentum space, which is an excellent illuminating source for high-quality imaging with an extremely low speckle noise. More importantly, a triple-state color-switchable random laser with yellow, red and yellow-red dual-colors can be flexible, and is obtained by simply moving the pump position. The results may promote the practical applications of random lasers in the fields of sensing, in vivo biological imaging, and high brightness full-field illumination.