Alexander Laskin

Achromatic refractive beam shaping optics for broad spectrum laser applications

The task of providing the same conditions of intensity profile transformation for a broad spectral bandwidth can be solved by refractive beam shaping optics with achromatic design. This solution is important for various scientific and industrial applications including confocal microscopy, biomedical fluorescence techniques, some industrial technologies and many tasks based on short pulse lasers where a bandwidth of up to hundreds of nm is to be provided. The design of achromatic refractive beam shapers is based on applying of materials of different dispersion characteristics and provides necessary intensity distribution transformation simultaneously for laser beams in wide spectral range. These achromatic beam shapers keep the resulting intensity distribution over a long distance, operate with collimated and divergent beams and provide easy adaptation to specifications of real lasers. This paper will describe some design examples of achromatic beam shapers optimized to be used with short pulse lasers like Ti:Sapphire or Yb:KGW ones in infrared and ultraviolet spectrum. There will be presented results of applying achromatic laser beam shapers with short pulse lasers in such applications as irradiating the cathode of Free Electron Lasers, processing of photovoltaic materials.

Variable beam shaping with using the same field mapping refractive beam shaper

Modern laser scientific techniques and industrial technologies require not only simple homogenizing of a beam but also more freedom in manipulation of intensity profile and generating such profiles like super-Gaussian, inverse-Gaussian, skewed flattop and others. In many cases the task of variable beam shaping can be solved by refractive beam shaping optics of field mapping type which operational principle presumes saving of beam consistency, providing collimated output beam of low divergence, high transmittance and flatness of output beam profile, extended depth of field; another important feature is negligible residual wave aberration. Typically the fields mapping refractive beam shapers, like πShaper, are designed to generate flattop intensity profile for a beam of pre-determined size and input intensity profile. Varying of the input beam diameter lets it possible to realize either super-Gaussian (smaller input) or inverse-Gaussian (bigger input) intensity profiles of output beam that are important in pumping of solid-state lasers, hardening, cladding and other techniques. By lateral shift of a beam with respect to a πShaper the output flattop profile gets a skew in direction of that shift, the skew angle corresponds to the shift value. The skewed profile is important, for example, in some acousto-optical techniques where compensation of acoustic wave attenuation is required. All variety of profiles can be provided by the same beam shaper unit. This paper will describe some design basics of refractive beam shapers of the field mapping type and techniques to vary the output intensity profile, experimental results will be presented as well.

Imaging techniques with refractive beam shaping optics

Applying of the refractive beam shapers in real research optical setups as well as in industrial installations requires very often manipulation of a final laser spot size. In many cases this task can be easily solved by using various imaging optical layouts presuming creating an image of a beam shaper output aperture. Due to the unique features of the refractive beam shapers of field mapping type, like flat wave front and low divergence of the collimated resulting beam with flattop or another intensity profile, there is a freedom in building of various imaging systems with using ordinary optical components, including off-the-shelf ones. There will be considered optical layouts providing high, up to 1/200×, de-magnifying factors, combining of refractive beam shapers like πShaper with scanning systems, building of relay imaging systems with extended depth of field. These optical layouts are widely used in such laser technologies like drilling holes in PCB, welding, various micromachining techniques with galvo-mirror scanning, interferometry and holography, various SLM-based applications. Examples of real implementations and experimental results will be presented as well.

Applying of refractive beam shapers of circular symmetry to generate non-circular shapes of homogenized laser beams

Creating of non-circular laser spots, for example of linear, elliptical or rectangle shape, with uniform intensity profile is important in various laser techniques in industry, scientific and medical applications. This task can be successfully solved with applying of refractive beam shaping optics of field mapping type in combination with some additional optical components. Due to their unique features, such as: low output divergence, high transmittance and flatness of output beam profile as well as extended depth of field, the refractive field mappers provide a freedom in further manipulation with intensity profile and shape of a laser beam. Typically design of refractive field mapping beam shapers has circular symmetry; therefore creating of non-circular spot shapes requires applying anamorphic optical components (cylinder lenses, prism pairs, etc.) ahead of or after a beam shaper. As result it becomes possible to provide various combinations of spot shape and intensity profiles, for example: roof-like spot with uniform intensity in one direction and Gaussian or triangle profile in another direction, linear spots with aspect ratio up to 1:1000, elliptical spots of uniform intensity, etc. Applications include flow cytometry instrumentation, particle image velocimetry, particle size analyzing, hardening, cladding, annealing, and others. This paper will describe some design basics of refractive beam shapers of the field mapping type and optical layouts for creating laser spots of non-circular symmetry. Examples of real implementations will be presented as well.

Applying refractive beam shapers in creating spots of uniform intensity and various shapes

Different scientific and industrial laser techniques require not only intensity profile transformation but also creating various shapes of final spots like circles of different diameter, lines and others. As a solution it is suggested to apply combined optical systems consisting of a refractive beam shaper of field mapping type providing a required intensity transformation and additional optical components to vary the shape of final spots. The said beam shapers produce low divergence collimated flattop beam that makes it easy to vary the shape of the beam spot with using either ordinary relay imaging optics, including zoom one, or anamorphotic optics. And the design features of the refractive beam shapers allow controlling the intensity distribution in the final spot (most often flattop one) and providing wide range of spot sizes. This paper will describe some design examples of combined beam shaping systems to create round spots of variable diameter as well as linear spots of uniform intensity. There will be presented results of applying these systems in such applications as laser hardening and others.

πShaper – Refractive Beam Shaping Optics for Advanced Laser Technologies

Laser beam shaping brings to various industrial and scientific laser techniques effects that improve their performance comparing to what can be achieved with using Gaussian or Gaussian-like laser beams: more stability, less tough positioning tolerances make the technologies easier to use, higher efficiency of using of costly laser energy, etc. The task of such a transformation is solved by series of refractive beam shaping optics of field mapping type. This solution is important in irradiating the cathode of Free Electron Lasers, confocal microscopy, biomedical fluorescence techniques, many industrial technologies like welding, cladding, hardening, various laser techniques in photovoltaics, homogenizing of pump radiation by building powerful femtosecond lasers, etc. The refractive beam shapers can be used with TEM00 and multimode laser beams, achromatic design provides the same conditions of beam shaping for several lasers of a certain spectrum range simultaneously, low inherent losses allow to use them with powerful laser sources, particular models can be implemented as Galilean Telescope without internal focusing or as Collimators. This paper will describe the principles of operation, design features of the achromatic refractive beam shapers; there will be presented examples of beam intensity transformation and effects on material processing achieved in several industrial applications.

Applying of refractive spatial beam shapers with scanning optics

Using of refractive beam shapers with laser scanning optics is often considered in realizing various industrial laser technologies as well as techniques used in scientific and medical applications. Today the galvo mirror scanners with F-theta, telecentric or other lenses as well as gantry systems are widely used in different applications like micromachining, solar cell manufacturing, microwelding, drilling holes, selective laser melting and others which performance can be improved by applying of beam shaping optics. And, due to unique features like low output beam divergence, high transmittance as well as extended depth of field and capability to generate various beam profiles, the refractive field mappers provide a freedom in building an optimum optical system. There will be considered some basic theoretical features of choosing an optimum refractive beam shaper and building systems on its base, as well as several optical layouts with beam shapers πShaper to generate laser spots of uniform intensity which sizes span from several tens of microns to millimetres. Examples of real implementations will be presented as well.Using of refractive beam shapers with laser scanning optics is often considered in realizing various industrial laser technologies as well as techniques used in scientific and medical applications. Today the galvo mirror scanners with F-theta, telecentric or other lenses as well as gantry systems are widely used in different applications like micromachining, solar cell manufacturing, microwelding, drilling holes, selective laser melting and others which performance can be improved by applying of beam shaping optics. And, due to unique features like low output beam divergence, high transmittance as well as extended depth of field and capability to generate various beam profiles, the refractive field mappers provide a freedom in building an optimum optical system. There will be considered some basic theoretical features of choosing an optimum refractive beam shaper and building systems on its base, as well as several optical layouts with beam shapers πShaper to generate laser spots of uniform intensity whic...

Refractive beam shapers for material processing with high power single mode and multimode lasers

The high power multimode fiber-coupled laser sources, like solid state lasers or laser diodes as well as single mode and multimode fiber lasers, are now widely used in various industrial laser material processing technologies like metal or plastics welding, cladding, hardening, brazing, annealing. Performance of these technologies can be essentially improved by varying the irradiance profile of a laser beam with using beam shaping optics, for example, the field mapping refractive beam shapers like piShaper. Operational principle of these devices presumes transformation of laser beam irradiance distribution from Gaussian to flattop, super-Gauss, or inverse-Gauss profile with high flatness of output wave front, conserving of beam consistency, providing collimated output beam of low divergence, high transmittance, extended depth of field. Important feature of piShaper is in capability to operate with TEM00 and multimode lasers, the beam shapers can be implemented not only as telescopic optics but also as collimating systems, which can be connected directly to fiber-coupled lasers or fiber lasers, thus combining functions of beam collimation and irradiance transformation. This paper will describe some features of beam shaping of high-power laser sources, including multimode fiber coupled lasers, and ways of adaptation of beam shaping optical systems design to meet requirements of modern laser technologies. Examples of real implementations will be presented as well.

Developing the refractive light beam shapers as lossless apodization systems suppressing the side-lobes in Fourier transform optical systems

The Fourier transform optical systems, creating an image and/or realizing its accurate spectral characterization, suffer from appearing remarkable level of side-lobes in the image intensity distribution that reduce performances, in particular, the dynamic range of these systems. Therefore, suppressing side-lobes in the image plane represents an actual practical task being important for various scientific and technical applications such as, for example, direct imaging and spectral characterization of Earth-like extra-solar planets or spectrum analysis of ultra-high frequency radio-wave signals with exploiting an advanced acousto-optical technique. We suggest applying as apodization systems novel refractive optical beam shapers of the field mapping type, which are able to convert the input (more or less) uniform intensity distribution, peculiar to the majority of usually exploited sources of light, to arbitrary pre-scripted intensity distributions. In the case of choosing, for instance, Gaussian, cosine on a pedestal, etc. distributions, these shapers make it possible to minimize the total level of side-lobes significantly and to increase, in doing so, the dynamic range of optical data processing up to 40 dB or more. The operation principle of these beam shapers is based on inducing, in a control manner, spherical aberration in order to provide the required intensity profile transformation and further compensation of that aberration. As a result, the beam shapers operate as telescopes of special type; they produce a low divergence collimated beam with a target intensity distribution and flat wave front. We describe the beam shaper design, implementation examples, and results of practical applications to the acousto-optical technique of precise multi-channel spectrum analysis.

Beam shaping in high-power laser systems with using refractive beam shapers

Beam Shaping of the spatial (transverse) profile of laser beams is highly desirable by building optical systems of high-power lasers as well in various applications with these lasers. Pumping of the crystals of Ti:Sapphire lasers by the laser radiation with uniform (flattop) intensity profile improves performance of these ultrashort pulse high-power lasers in terms of achievable efficiency, peak-power and stability, output beam profile. Specifications of the solid-state lasers built according to MOPA configuration can be also improved when radiation of the master oscillator is homogenized and then is amplified by the power amplifier. Features of building these high power lasers require that a beam shaping solution should be capable to work with single mode and multimode beams, provide flattop and super-Gauss intensity distributions, the consistency and divergence of a beam after the intensity re-distribution should be conserved and low absorption provided. These specific conditions are perfectly fulfilled by the refractive field mapping beam shapers due to their unique features: almost lossless intensity profile transformation, low output divergence, high transmittance and flatness of output beam profile, extended depth of field, adaptability to real intensity profiles of TEM00 and multimode laser sources. Combining of the refractive field mapping beam shapers with other optical components, like beam-expanders, relay imaging lenses, anamorphic optics makes it possible to generate the laser spots of necessary shape, size and intensity distribution. There are plenty of applications of high-power lasers where beam shaping bring benefits: irradiating photocathode of Free Electron Lasers (FEL), material ablation, micromachining, annealing in display making techniques, cladding, heat treating and others. This paper will describe some design basics of refractive beam shapers of the field mapping type, with emphasis on the features important for building and applications of high-power laser sources. There will be presented results of applying the refractive beam shapers in real installations.