CQT Seminar: Cosmas Mafusire (Mathematical Optics Group, CSIR NLC)
THE QUANTUM RESEARCH GROUP,
Cordially invite you to attend a
QUANTUM TECHNOLOGY COLLOQUIUM
MODELLING AND MEASUREMENT OF OPTICAL ABERRATIONS OF LASER BEAMS PROPAGATING THROUGH RANDOM MEDIA
Presented by
MR COSMAS MAFUSIRE
Student Employee, Mathematical Optics Group,
CSIR National Laser Centre
ABSTRACT:
When laser beams propagate through random media, the phase of the filed is altered in such a way as to reflect the properties of the medium. The phase alterations or distortions to the phase are called aberrations. We used the Zernike formalism to represent the aberrations. We present a detailed study of the impact of aberrations on t he beam quality factor and field curvature. This has led us to closed formulae for
calculating the beam quality factor (M2) and the mean focal length of an abberated lens from Zernike aberration coefficients, models which we verified experimentally using phase-only spatial light modulator to generate aberrations and a Shack-Hartmann wavefront sensor for measurement. We used these formulae to characterise a spinning pipe gas lens (SPGL) and the flame lens by studying their computational fluid dynamics (CFD) models. From the density data, we calculated the phase using the Gladstone-Dale l aw from which we generated the Zernike coefficients and thus M2, focal length as well as the Strehl ratio generated by these devices. We then went on to perform experimental instigation of the lenses verifying the CFD model in the process. The last thing we did was study the turbulence generated by the SPGL using classical turbulence models showing that as its rotation speed and temperature increases, its turbulence became stronger.
DATE: 21.11.2011
TIME: 12h00
VENUE: NITheP Seminar Room, Level 3, H-Block, Westville Campus