Forced air cooling of volume Bragg gratings for spectral beam combination

Anderson, Brian; Kaim, Sergiy; Venus, George; Lumeau, Julien; Smirnov, Vadim; Zel'dovich, Boris Ya; Glebov, Leonid

doi:10.1117/12.2005951

Cited by 4 publications

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“…Such thermal effect was not observed when combining only reflected beams because they penetrated the MVBG significantly less and therefore much less of their power was absorbed and dissipated as heat into the glass. Using better cooling techniques such as surface air-flow can eliminate the thermal effect and the resulting beam quality degradation observed [17]. In conclusion, the use of multiplexed volume Bragg gratings for spectral beam combining is excellent alternative and addition to the current state of the art combining techniques.…”

Section: Spectral and Coherent Laser Beam Combining By Volume Bragg Gmentioning

confidence: 96%

“…Another PTR advantage is its very low losses-on the order of 10 −5 cm −1 . Testing of VBG recorded in the PTR glass performed under irradiation of 9 kW CW with a 6-mm-diameter spot showed heating that did not exceed 15 K [17]. Even though small heating effects lead to thermal variations of the refractive index of the glass (dn/dt = 5 × 10…”

Section: Recording Materialsmentioning

confidence: 99%

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Volume Bragg Gratings: Fundamentals and Applications in Laser Beam Combining and Beam Phase Transformations

Divliansky¹

2017

Holographic Materials and Optical Systems

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Two major volume Bragg grating (VBG) applications will be presented and in particular laser beam combining and holographically encoded phase masks. Laser beam combining is an approach where multiple lasers are combined to produce more power. Spectral beam combining is a technique in which different wavelengths are superimposed spatially (combined) using a dispersive element such as a volume Bragg grating. To reduce the complexity of such combining system instead of multiple individual VBGs, it will be demonstrated that a single holographic element with multiple VBGs recorded inside could be used for the same purpose. Similar multiplex volume holographic elements could be used for coher ent beam combining. In this case, the gratings operate at the same wavelength and have degenerate output. Such coherent combining using gratings written in photothermorefractive (PTR) glass will be discussed. The chapter also demonstrates that binary phase profiles may be encoded into volume Bragg gratings, and that for any probe beam capable of satisfying the Bragg condition of the hologram, this phase profile will be present in the diffracted beam. A multiplexed set of these holographic phase masks (HPMs) can simultaneously combine beams while also performing mode conversion. An approach for making HPMs fully achromatic by combining them with a pair of surface gratings will be outlined.Keywords: holography, volume Bragg gratings, beam combining, phase plates, photothermo refractive glass, multiplexed volume gratings © 2017 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Volume Bragg gratings Description and propertiesVolume grating as its name suggest is a grating that occupies the volume of a medium. Typically, for such gratings the term volume Bragg gratings (VBGs) is used in relation to Sir William Bragg who in 1915 used diffraction of light propagating through a crystal to determine the crystal's lattice structure [1]. What he found was that at certain conditions the light is strongly diffracted by the crystal. Such condition is called "resonant condition" or also "Bragg condition." Here is also the place to make the distinction between surface and volume Bragg gratings. If we start with a surface grating and start increasing its thickness at some point the different diffraction orders will reduce to a moment where there will be only one order. This defines the transition to a volume grating behavior [2].There are two basic types of VBGs which is shown in Figure 1. The first one is a transmission Bragg grating (TBG) for which if the incident light satisfies the Bragg condition it is not transmitted but also diffracted. The second type is a reflection Bragg grating (RBG) which behaves like a mirror for incoming light that matches the Bragg condition.For simplicity, in Figure 1, fo...

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Section: Spectral and Coherent Laser Beam Combining By Volume Bragg Gmentioning

confidence: 96%

Section: Recording Materialsmentioning

confidence: 99%

Volume Bragg Gratings: Fundamentals and Applications in Laser Beam Combining and Beam Phase Transformations

Divliansky¹

2017

Holographic Materials and Optical Systems

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“…Further detriment to beam quality occurs from higher order aberrations which will affect the M 2 of single beams interacting with the heated VBG. Such effects have been quantified in [11]. At much higher optical power densities, or for VBGs with higher levels of absorption, the analysis of thermal effects from transmitted and reflected beams requires more in depth analysis techniques [12].…”

Section: Three Channel High Power Beam Combiningmentioning

confidence: 99%

Scaling the spectral beam combining channels in a multiplexed volume Bragg grating

Ott¹,

Divliansky²,

Anderson³

et al. 2013

Opt. Express

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In order to generate high power laser radiation it is often necessary to combine multiple lasers into a single beam. The recent advances in high power spectral beam combining using multiplexed volume Bragg gratings recorded in photo-thermo-refractive glass are presented. The focus is on using multiple gratings recorded within the same volume to lower the complexity of the combining system. Combining of 420 W with 96% efficiency using a monolithic, multiplexed double grating recorded in PTR glass is demonstrated. A multiplexed quadruple grating that maintains high efficiency and good beam quality is demonstrated to pave a way for further scaling of combining channels.

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“…affecting the transmitted beam [19]. Here we record phase masks in the bulk of the glass by utilizing the contact-copy method and a specialized amplitude mask.…”

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confidence: 99%

Beam shaping by volume phase structures in photo-thermo-refractive glass

et al. 2013

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We demonstrate the recording of volume phase masks in the bulk of photo-thermo-refractive glass. Recording was produced by exposing the glass to UV radiation through binary amplitude masks. Depending on the profile of the amplitude mask either a binary volume phase mask or a grayscale phase mask may be produced. Volume phase masks have been used to generate Fresnel lenses, convert a Gaussian beam into higher order Hermite-Gauss and LaguerreGauss modes, to produce optical vortices, and to create aberration-correcting optical components.Phase masks have been used for decades for a variety of applications, including improving the depth of field [1-3], manufacture of electronics [4], encryption [5][6][7][8], and coronagraphy [9][10][11]. Conventional fixed phase masks are generally produced by either sculpting the surface of a thin film such as PMMA or by recording it in the bulk of a photosensitive material such as DCG or lithium niobate. Active phase masks may also be produced using spatial light modulators. In either case these masks may be used effectively in low power systems as they can be designed to have nearly any phase profile. However, such elements have several drawbacks as well. Absorption in these materials prevents them from being used in high power systems, and thin film and SLM phase masks may also be damaged from mishandling or by placement in high temperature conditions. In order to have a robust phase mask suitable for use in such systems it is therefore necessary to utilize a low-absorption substrate with the phase mask recorded in the bulk to prevent damage via mishandling. Here we present a method for recording volume phase masks (VPMs) in the bulk of photo-thermo-refractive (PTR) glass.PTR glass is a sodium-potassium-zinc-aluminum-fluorine-bromine-silicate glass doped with cerium, antimony, tin, and silver, with a region of transparency from 350 nm to 2700 nm and a damage threshold of 40 J/cm 2 [12,13]. Due to this wide transparency window, PTR glass is used to produce volume Bragg gratings for the visible and infrared regions, which have found applications in pulse stretching and compression [14], beam combining [15,16], and ultra-narrow spectral filtering [17,18]. In the near IR region PTR glass has an absorption coefficient of ~10 -4 cm -1 , which, coupled with its glass transition temperature of ~460 o C [12], makes a suitable substrate for high power and high temperature systems. In addition, forced air cooling can be applied to the sample without degrading the recorded profile or seriously Mask PTR Sample f z Fiber delivery from UV lamp Fig. 1: Recording geometry for producing a phase mask using the contact-copy technique.

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Forced air cooling of volume Bragg gratings for spectral beam combination

Cited by 4 publications

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Volume Bragg Gratings: Fundamentals and Applications in Laser Beam Combining and Beam Phase Transformations

Volume Bragg Gratings: Fundamentals and Applications in Laser Beam Combining and Beam Phase Transformations

Scaling the spectral beam combining channels in a multiplexed volume Bragg grating

Beam shaping by volume phase structures in photo-thermo-refractive glass

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