Abstract
When the walls of an open-ended horizontal steel pipe are heated before the pipe is rotated along its axis, the exchange of the expelled heated air with the incoming cooler air, sucked in along the axis, results in a medium capable of focusing a laser beam propagating along the pipe’s axis – a spinning pipe gas lens. However, the interaction of the heated and cooler air generates local density fluctuations which generate aberrations on the laser beam wavefront. We present results for the characterisation of these aberrations using a Shack- Hartmann wavefront sensor. The measurements show that along the axis, rotating the pipe decreases y-tilt as a result of the removal of distortions caused by gravity, although there is an increase in higher-order aberrations. However, in the boundary layer, the dominant aberration is x-astigmatism which increases with rotation speed. The results are confirmed by the measurement of the beam quality factor which increases as a result of the increase in the size of the higher-order aberrations. The spinning pipe gas lens is a device which can be used to focus laser beams using air only, but, in the process, the air introduces distortions which reduce the quality of the beam.
Highlights
We explored the aberrations generated by a heated spinning pipe – an open-ended steel pipe heated and rotated along its axis
It is well known that the resulting density distribution inside the pipe is conducive to focusing laser beams through the gradient index (GRIN) lens principle.[1,2,3,4,5,6,7,8]
The spinning pipe gas lens was invented by Martynenko[1], and was subsequently developed for use as a ‘damage-free’ lens for focusing of high-power laser fields,[2,3,4] and as a gas telescope for astronomical imaging[6]
Summary
We explored the aberrations generated by a heated spinning pipe – an open-ended steel pipe heated and rotated along its axis. The centre of the pipe is dominated by rotational flow with little exchange with the environment, which results in the density distribution of the gas lens shown, as calculated from the CFD model. We present results from aberration measurements generated by an SPGL on a HeNe laser beam transmitted through the SPGL’s axis and boundary layer.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
