The native shape of the single-mode laser beam used for high power material processing applications is circular with a Gaussian intensity profile. Manufacturers are now demanding the ability to transform the intensity profile and shape to be compatible with a new generation of advanced processing applications that require much higher precision and control. We describe the design, fabrication and application of a dual-optic, beam-shaping system for single-mode laser sources, that transforms a Gaussian laser beam by remapping – hence field mapping - the intensity profile to create a wide variety of spot shapes including discs, donuts, XY separable and rotationally symmetric. The pair of optics transform the intensity distribution and subsequently flatten the phase of the beam, with spot sizes and depth of focus close to that of a diffraction limited beam. The field mapping approach to beam-shaping is a refractive solution that does not add speckle to the beam, making it ideal for use with single mode laser sources, moving beyond the limits of conventional field mapping in terms of spot size and achievable shapes. We describe a manufacturing process for refractive optics in fused silica that uses a freeform direct-write process that is especially suited for the fabrication of this type of freeform optic. The beam-shaper described above was manufactured in conventional UV-fused silica using this process. The fabrication process generates a smooth surface (<1nm RMS), leading to laser damage thresholds of greater than 100J/cm2, which is well matched to high power laser sources. Experimental verification of the dual-optic filed mapper is presented.
The increasing demand for bandwidth is driving the development of new paradigms within the fibre optic telecomms industry and leading to the generation of a new range of optical components. One route being taken is the hybridization of discrete components into a single package to realize high functionality subsystems. The combination of MEMS with light guide technology is one hybridization pathway that is showing considerable potential. In the drive for novel functionality it is paramount that the performance parameters are not compromised, nor should the hybridization of discrete components lead to increased manufacturing and packaging complexity and reliability issues. A theoretical and experimental study of integration schemes has shown that it is possible to integrate MEMS components with light guide technologies using just simple air gaps while preserving key performance parameters.
Diffractive optical elements to modify laser beam spatial intensity distributions are described. The elements have been applied to free-space Gaussian to flat-top beam conversion and customization of the modes of a laser resonator. The single pass free space elements demonstrate a high efficiency but result in to much high frequency noise on the beam. The intra-cavity elements significantly altered the TEM00 profile but practical limitations with the positioning of the element within the cavity prevented operation in the design mode.
We propose to use dynamic ternary phase-amplitude modulation for free-space reconfigurable optical interconnections, and demonstrate its significant advantages over the widely- adopted binary-phase scheme.
Scalar and resonance domain diffractive optical elements are proposed for use within high power laser systems. Resonance domain elements are described for beam deflection and polarization selection. Scalar domain elements for harmonic separation filtering and beam shaping in the near- and far- fields are also described. Experimental results are presented for far-field beam shaping and harmonic separation filtering elements.
A high power, two-dimensional, 16 by 4 element waveguide array carbon-dioxide laser is presented and properties such as beam quality and spatial power distribution are assessed, together with beam reformatting techniques to produce compact beams.
This paper reports on the development of several diffractive optical elements (DOE) to fulfill applications on high power Nd glass laser systems. The measured performance for those components realized is discussed. These are focusing beam samplers, beam shapers, and harmonic separation filters (HSF). Designs of more demanding components operating in the resonance domain are also presented. These are linear polarizing elements and beam deflectors.