Modelling the formation of optical waveguides produced in LiNbO3 by laser induced thermal diffusion of lithium ions

Muir, A.C.; Daniell, G.J.; Please, Colin P.; Wellington, I.T.; Mailis, S.; Eason, R.W.

doi:10.1007/s00339-006-3493-4

Cited by 28 publications

(23 citation statements)

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“…UV illumination leads to photoexcitation of charges and heating of the crystal. 16 A pyroelectric field is formed which drives electrons into the bulk of the crystal and holes toward the surface, producing a short range dipolar electric field distribution, which increases the coercive field locally. When a domain nucleates on the −z face and propagates toward +z face, inversion will not occur in this region where the coercive field is increased and domain propagation will be impeded, leaving a +z surface domain island on a −z background.…”

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Precision nanoscale domain engineering of lithium niobate via UV laser induced inhibition of poling

Sones

Muir

Ying

et al. 2008

Applied Physics Letters

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Continuous wave ultraviolet laser irradiation at = 244 nm on the +z face of undoped and MgO doped congruent lithium niobate single crystals has been observed to inhibit ferroelectric domain inversion. The inhibition occurs directly beneath the illuminated regions, in a depth greater than 100 nm during subsequent electric field poling of the crystal. Domain inhibition was confirmed by both differential domain etching and piezoresponse force microscopy. This effect allows the formation of arbitrarily shaped domains in lithium niobate and forms the basis of a high spatial resolution microstructuring approach when followed by chemical etching. © 2008 American Institute of Physics. ͓DOI: 10.1063/1.2884185͔ Domain engineering 1,2 of lithium niobate ͑LN͒ is a subject of extensive research and a simple, cheap, and robust method of fabrication of well-defined periodic domaininverted structures on submicron scales is highly desirable. Spatial domain engineering is used for many optical processes in bulk crystals and waveguides and can also allow for the creation of both freestanding 3 and surface relief structures 4 through the differential etching characteristics of the polar z faces of the crystal. If achievable on the submicron scale, surface structuring through differential etching will allow the implementation of a range of interesting applications such as tunable photonic crystals, ridge waveguide lasers, and multifunctional micromachines.Previous work has shown that ultraviolet ͑UV͒ and visible laser light can either directly invert 5 or assist the domain inversion process in LN. [6][7][8][9] In this paper, however, a different effect is presented whereby illumination of the +z face with UV light at = 244 nm ͑with photon energy greater than the LN band gap͒ inhibits domain inversion in illuminated areas during subsequent electric field poling ͑EFP͒. Of major importance, the inhibited domains are not restricted in their shape or alignment with the crystal x or y axes, hence, arbitrarily shaped domains can be formed. Some initial results of this effect and its applicability in the creation of micro/nano structures in LN are presented.A beam from a frequency-doubled Ar-ion laser was focused to a spot size of ϳ2.5 m on the +z or −z face of either an undoped congruent or 5 mol % MgO-doped LN crystal. Positioning and exposure control of the crystal was achieved by a computer-controlled, three-axis stage system coupled with a mechanical shutter.For dynamic exposures, sets of parallel lines were drawn on the z faces of the crystals along the crystallographic x or y directions by moving the stages at speeds ranging from 0.05 to 0.3 mm s −1 . For static exposures, arrays of illuminated spots with identical exposure times, ranging from a few milliseconds to a few tens of seconds, were formed. The separation between the edges of adjacent illuminated spots in the arrays varied from 0 to 6 m which permitted us to verify if any proximity effect existed such as that observed in pulsed laser direct poling 5 where the closest approa...

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Precision nanoscale domain engineering of lithium niobate via UV laser induced inhibition of poling

Sones

Muir

Ying

et al. 2008

Applied Physics Letters

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“…After an intense 250-kHz femtosecond laser is tightly focused in a glass sample, glass network modifiers, such as alkaline ions and alkaline-rare-earth ions, are proved to migrate away from the centre of the focal point in a range of a few tens of micrometers. Investigation of the behaviour of ion migration is important for theoretical understanding the change of refractive index inside glasses, which is essential to the laser-writing waveguides [6,9,10]. At present, there are different types of waveguides in various transparent materials [11][12][13].…”

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Elemental redistribution in glass induced by a 250-kHz femtosecond laser

Luo¹,

Geng²,

Pan³

et al. 2011

Journal of Non-Crystalline Solids

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“…The short absorption depth suggests that the optical waveguide formation cannot be explained by a direct optical photorefractive effect as the volume where a refractive index change occurs in order to support a waveguide mode should be much larger that the volume where the light is absorbed. However, the model which was presented in [21] suggests that the heated volume, due to the UV laser irradiation, is much larger as compared to the UV radiation absorption depth. This prediction offers the alternative route of a heat driven mechanism that could be responsible for the observed refractive index change.…”

Section: Uv Laser Induced Effectsmentioning

confidence: 99%

“…The diffusion of heat after UV laser irradiation and the formation of temperature gradients has been studied in [21] in an attempt to explain the observation that optical waveguides could be directly written in LN by UV laser irradiation at 244 nm [22]. The literature value for the absorption depth at 244 nm radiation is of order ~30 nm.…”

Section: Uv Laser Induced Effectsmentioning

confidence: 99%

“…Additionally, the pulsed lasers which were used in these experiments could only operate at repetition rates up to 100 Hz. According to [21] the duration of the full heat/cooling cycle can be much faster than the 10 ms, which is the minimum time interval between subsequent pulses, hence no cumulative heat effects were expected. This prediction is in accordance with the experimental observation.…”

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confidence: 99%

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UV laser induced ferroelectric domain inversion in lithium niobate single crystals

Mailis

2010

J. Opt.

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Abstract. UV radiation in the spectral region beyond ~320 nm is strongly absorbed by lithium niobate single crystals. The strong absorption and the consequent localized heating of the crystal triggers physical processes which can affect the state of the material not only by changing the refractive index, as shown in the past, but also by changing its ferroelectric disposition. UV laser irradiation of the polar surfaces in particulars can induce or inhibit the inversion of ferroelectric domains. A summary of these UV light induced effects and their utility in the micro-structuring of this very important optical ferroelectric crystal will be presented here.

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Modelling the formation of optical waveguides produced in LiNbO3 by laser induced thermal diffusion of lithium ions

Cited by 28 publications

References 10 publications

Precision nanoscale domain engineering of lithium niobate via UV laser induced inhibition of poling

Precision nanoscale domain engineering of lithium niobate via UV laser induced inhibition of poling

Elemental redistribution in glass induced by a 250-kHz femtosecond laser

UV laser induced ferroelectric domain inversion in lithium niobate single crystals

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