Technical Papers and Publications

PAPER SUMMARY YEAR AND DOI

 

Customised low-angle refractive diffusers for high power laser applications

Author(s): M. Currie*, P. Blair, T.E.B. Murphy, R. McBride

Abstract: We describe the design and fabrication of smooth and continuous customized refractive diffusers for the beamshaping of high power lasers, specifically laser systems in which a low diffusion angle is required. Traditional diffusers often have randomised surfaces with strong high frequency peaks in their spatial frequency content.

2016. SPIE

Field Mappers for Laser Material Processing

Author(s):Paul Blair*, Matthew Currie, Natalia Trela, Howard J. Baker, Eoin Murphy, Duncan Walkerb, and Roy McBride

Abstract: 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.

2106. SPIE

Rapid manufacture of freeform micro-optics for high power applications

Author(s): Matthew Currie ; Roy McBride

Abstract: We report a new route to obtaining custom freeform micro-optical components that is free from symmetry restrictions, offering drastically lower cost and delivery times than what is required by other freeform manufacturing methods. We describe how this process can be used to realize a complex custom optic using data generated directly from a design in Zemax.

2014. SPIE
doi:10.1117/12.2040140

Monolithic fast-axis collimation of diode laser stacks

Author(s): Roy McBride; Natalia Trela; Matthew O. Currie; Jozef J. Wendland; Howard J. Baker

Abstract: Commercially-available QCW diode laser stacks with bar pitch below 0.5mm can now deliver source power densities exceeding 10kW/cm2. An increasing number of applications for these sources also specify high brightness, with collimation requirements ranging from equalization of fast and slow axis divergence to achieving fast-axis divergence within a small multiple of the diffraction limit.

2013. SPIE
doi: 10.1117/12.2005232

Extending the locking range of VHG-stabilized diode laser bars using wavefront compensator phaseplates

Author(s): Roy McBride; Natalia Trela; Jozef J. Wendland; Howard J. Baker

Abstract: We describe the successful use of wavefront compensator phaseplates to extend the locking range of VHG-stabilized diode laser bars by correcting the effects of imperfect source collimation.

2011. SPIE
doi:10.1117/12.884202

Over 55W of frequency doubled light at 530 nm pumped by an all-fiber diffraction limited picosecond fibre MOPA

Author(s): Shaif-ul Alam; Kangkang Chen; John R. Hayes; Dejiao Lin; Andrew Malinowski; Howard J. Baker; Natalia Trela; Roy McBride; David J. Richardson

Abstract: We report the realisation of a high power, picosecond pulse source at 530 nm pumped by an all-fiber, single mode, single polarisation, Yb-doped MOPA. The pump MOPA comprised of a gain switched seed source generating 20 ps pulse source at a repetition frequency of 910 MHz followed by three amplification stages. Output power in excess of 100 W was obtained at 85% slope efficiency with respect to launched pump power at 975 nm.

2010. SPIE
doi: 10.1117/12.845929

Beam Reformatting and Combining of High-Power Laser Diode Stacks

Author(s): Howard J. Baker; N. Trela; D. R. Hall; R. McBride; J. J. Wendland

Abstract: Custom beam correction phase-plates developed for conserving brightness for diode laser bars in beam shaping/combining now provide multiple optical functions in one component, for new approaches to spatial, wavelength and coherent combining of arrays. 2010. Optical Society of America
doi: 10.1364/CLEO.2010.CThX2

56-W Frequency-Doubled Source at 530 nm Pumped by a Single-Mode, Single-Polarization, Picosecond, Yb-Doped Fiber MOPA

Author(s): Kang Kang Chen; Alam, S; Hayes, J.R; Baker, H.J.; Hall, D.; McBride, R; Price, J.H.V.; Dejiao Lin; Malinowski, A.; Richardson, D.J.

Abstract: We report a frequency-doubled green source at 530 nm pumped based on an all-fiber, picosecond, single-polarization Yb 3+-doped fiber master oscillator power amplifier (MOPA) delivering 20-ps pulses at user selectable repetition rates of up to 910 MHz and an average output power in excess of 100 W at 1.06 µm. The output of the MOPA was frequency-doubled using a lithium triborate crystal. Up to 56 W of green light was generated at a corresponding repetition rate of 227 MHz at an overall conversion efficiency of 56%. The diode-to-green optical power conversion efficiency was 37 2010. IEEE
doi: 10.1109/LPT.2010.2046633

Laser smoothing of binary gratings and multilevel etched structures in fused silica

Author(s): Krystian L. Wlodarczyk; Enrique Mendez; Howard J. Baker; Roy McBride; Denis R. Hall

Abstract: We describe a promising approach to the processing of micro-optical components, where CO2 laser irradiation in raster scan is used to generate localized surface melting of binary or multilevel structures on silica, fabricated by conventional reactive-ion etching. The technique is shown to provide well-controlled local smoothing of step features by viscous flow under surface tension forces, relaxing the scale length of etch steps controllably between 1 and 30 μm . 

2010. Optical Society of America
doi: 10.1364/AO.49.001997

Low-loss wavelength locking of a 49-element single mode diode laser bar with phase-plate beam correction

Author(s): Trela, N.; Baker, H.J.; McBride, R; Hall, D.R.

Abstract: The paper reports on the use of dual-axis correction for a full-length diode laser bar from Bookham, with 49 single mode emitters and 30 W cw output at 975 nm. Fast-axis smile and lens error correction is combined with laser-cut slow axis collimation to give highly parallel beams with far-field divergence of 2.6 mrad (fast axis) and 13 mrad (slow-axis). Result shows the improvement in fast-axis divergence, in the form of far-field pattern vs. emitter number.

2009. IEEE
doi: 10.1109/CLEOE-EQEC.2009.5192658

Beam shapers for high power lasers, fabricated by laser micro-machining

Author(s): Baker, H.J; Ott, C.; McBride, R.M; Wendland, J.J.; Hall, D.R.

Abstract: Beam shaping by arbitrary shaped refractive surfaces is achieved with laser micro-machined and smoothed silica. The technique provides custom circular and rectangular flat-tops beams suitable for high intensity, modern fibre lasers. 2009. IEEE

Beam conditioning of high power diode lasers

Author(s): McBride, R.

Abstract: PowerPhotonic's fabrication process allows the economic manufacture of application-specific and devicespecific micro-optics without incurring high tooling costs. The flexibility of this process allows a wide range of optical functions to be implemented, including wavefront compensators, slow-axis collimators and beam transformers. The process allows multiple functions to be integrated into a single optic, resulting in a simpler system design and a reduced bill of materials.

2009. IEEE
doi:
10.1109/HPD.2009.5362876

External cavity phase-locked semiconductor tapered lasers

Author(s): Hassiaoui; N. Michel; M. Lecomte; O. Parillaud; M. Calligaro; M. Krakowski; R. McBride; G. Bourdet; J.-P. Huignard

Abstract: This work relates to combining a phase corrected array of tapered laser diodes, emitting at λ = 975 nm, coherently using the Talbot effect. Diffractive coupling of semiconductor lasers by use of the Talbot effect provides a means for coherent beam addition of multiple elements in laser diode arrays and makes possible a very compact external cavity. We have used, in this work, fully index guided tapered laser diodes.

2008. SPIE
doi:10.1117/12.763398

1.8kW diode laser system for fibre-delivery using brightness-enhanced diode stacks and a novel final beam-shaper

Author(s):H. J. Baker; J. F. Monjardin; P. Kneip; D. R. Hall; R. McBride

Abstract: A 1.8kW diode laser source made up of 100 W diode bars is designed for fibre delivery, using two new techniques to enhance the delivered brightness and equalise the beam-parameter product. Custom corrective phase plates in laser-cut silica are attached permanently to the two stacks of ten bars, correcting bar smile and restoring a factor of 2.5 in lost brightness. 2008. SPIE
doi: 10.1117/12.762786

A high-brightness QCW pump source using a pre-aligned GRIN lens array with refractive beam correction

Author(s): Roy McBride; Howard Baker; Jean-Luc Neron; Sead Doric; Cristina Mariottini; Enzo Nava; Emanuele Stucchi; Paolo Milanesi

Abstract: We demonstrate a technique for collimating conduction-cooled QCW diode laser stacks that achieves very high brightness in a compact and robust package. First we collimate the bars in the fast-axis using a pre-aligned array of Doric GRIN cylindrical lenses, where each lens is oriented to correct the gross positioning errors of each bar. We then measure the residual beam errors using a proprietary wavefront mapping system, and fabricate a refractive wavefront correction phaseplate to effectively flatten the wavefront. The type of lens used exhibits particularly low aberration in the presence of misalignment, ensuring that the resultant wavefront can be effectively corrected.

2008. SPIE.
doi: 10.1117/12.765485

Diffraction coupling of semiconductor tapered lasers in a very compact external Talbot cavity 

Author(s): I. Hassiaoui; N. Michel; M. Lecomte; O. Parillaud; M. Calligaro; M. Krakowski; R. McBride; G. Bourdet; J.-P. Huignard 

Abstract: This work relates to combining a phase corrected array of tapered laser diodes, emitting at λ = 975 nm, coherently using the Talbot effect. Diffractive coupling of semiconductor lasers by use of the Talbot effect provides a means for coherent beam addition of multiple elements in laser diode arrays and makes possible a very compact external cavity. We have used, in this work, fully index guided tapered laser diodes. They contain a ridge waveguide, which acts as a modal filter, and a tapered section of increasing width, which provides high power. 2008. SPIE
doi: 10.1117/12.781132

Micro-Optical Fabrication Based on Laser Smoothing of Etched Structures 

Author(s): Krystian L. Wlodarczyk; Enrique Mendez; Howard J. Baker; Mohammad Taghizadeh; Roy McBride; Denis R. Hall 

Abstract: CO2 laser smoothing of reactive-ion-etched silica structures is shown to provide controlled relaxation of sharp step features. The process is promising for low light scatter microoptics production using binary or multi-level etched structures as precursors. 2008. Optical Society of America
doi:10.1364/OFT.2008.OWC2

A high-brightness QCW pump source using a pre-aligned 
GRIN lens array with refractive beam correction

Author(s): Roy McBride; Howard Baker; Jean-Luc Neron; Sead Doric; Cristina Mariottini; Enzo Nava; Emanuele Stucchi; Paolo Milanesi

Abstract: We demonstrate a technique for collimating conduction-cooled QCW diode laser stacks that achieves very high brightness in a compact and robust package. First we collimate the bars in the fast-axis using a pre-aligned array of Doric GRIN cylindrical lenses, where each lens is oriented to correct the gross positioning errors of each bar. We then measure the residual beam errors using a proprietary wavefront mapping system, and fabricate a refractive wavefront correction phaseplate to effectively flatten the wavefront. 2008. SPIE
doi: 10.1117/12.765485

1.8kW diode laser system for fibre-delivery using brightness-enhanced diode stacks and a novel final beam-shaper 

Author(s): H. J. Baker; J. F. Monjardin; P. Kneip; D. R. Hall; R. McBride 

Abstract: A 1.8kW diode laser source made up of 100 W diode bars is designed for fibre delivery, using two new techniques to enhance the delivered brightness and equalise the beam-parameter product. Custom corrective phase plates in laser-cut silica are attached permanently to the two stacks of ten bars, correcting bar smile and restoring a factor of 2.5 in lost brightness.

2008. SPIE
doi: 10.1117/12.762786

High-power, low-divergence, linear array of quasi-diffraction-limited beams supplied by tapered diodes 

Author(s): Gilbert L. Bourdet; Imen Hassiaoui; Roy McBride; J. F. Monjardin; Howard Baker; Nicolas Michel; Michel Krakowski. 

Abstract: We describe for the first time to our knowledge the performance for a linear array of tapered laser diodes with both fast- and slow-axis collimation using a microlens for fast-axis collimation and a laser-written phase plate for slow-axis collimation and correction of the residual fast-axis errors from lens aberrations, thermal lensing, astigmatism, pointing errors, and other wavefront distortions. The phase plate leads to M 2 factor reductions of 1.5 for the lensed array following the fast axis and 2.6 for the whole bar following the slow axis. 2007. Optical Society of America.
doi: 10.1364/AO.46.006297