Title
Wavefront-sensor-induced beam size error: Physical mechanism, sensitivity-analysis and correction method
Author
Koek, W.D.
van Zwet, E.J.
Contributor
Dorsch, F. (editor)
Publication year
2015
Abstract
When using a commonly-used quadri-wave lateral shearing interferometer wavefront sensor (QWLSI WFS) for beam size measurements on a high power CO2 laser, artefacts have been observed in the measured irradiance distribution. The grating in the QWLSI WFS not only generates the diffracted first orders that are required for introducing the shear, but also diffracts significantly into higher orders. Consequently, in the few millimeters of free space propagation between the QWLSI WFS grating and its imaging device, the beam size may increase significantly (particularly for infrared wavelengths). This error is typically not accounted for in the subsequent processing of measurement data. To gain insight in this undesirable behavior, physical models of the QWLSI WFS using both complex wave propagation and analytic propagation of the D4sigma beam diameter (and its associated M2) throughout the system have been developed. These models show excellent agreement to experimental data, and indicate that in typical situations the sensor-induced beam size error can easily be 40% or more. Although the QWLSI WFS may not originally be intended for beam size measurements, in most industrial applications cost- and volume limitations will often lead to multiple use of sensor data. To aid in the adequate implementation of a QWLSI WFS for determining beam size, the dependence of the sensor-induced beam size error on various system parameters has been determined (e.g. incoming beam size, grating-to-imager distance, grating geometry, wavelength). Using the presented models and guidelines, the sensor-induced beam size error may be minimized and corrected for.
Subject
Nano Technology
OPT - Optics
TS - Technical Sciences
High Tech Systems & Materials
Electronics
Industrial Innovation
Beam diameter
Beam size error
D4sigma
Quadri-wave lateral shearing interferometer
QWLSI WFS
Sensor-induced beam size error
Carbon dioxide lasers
Data handling
Electric appliances
High power lasers
Interferometers
Laser diagnostics
Sensitivity analysis
Shearing
Wave propagation
Lateral shearing interferometer
QWLSI WFS
Wavefront sensors
Wavefront propagation
Laser materials processing
To reference this document use:
http://resolver.tudelft.nl/uuid:245a0c6a-58c0-4d86-b26c-e635aacf1366
TNO identifier
526110
Publisher
SPIE
ISBN
9781628414462
ISSN
0277-786X
Source
High-Power Laser Materials Processing: Lasers, Beam Delivery, Diagnostics, and Applications IV, 10-12 February 2015, San Francisco, CA, USA, 9356
Article number
935604
Document type
conference paper