Formation of collimated beams behind the woodpile photonic crystal

Trull, J.; Maigytė, Lina; Mizeikis, Vygantas; Malinauskas, Mangirdas; Juodkazis, Saulius; Cojocaru, C.; Rutkauskas, Marius; Peckus, M.; Sirutkaitis, Valdas; Staliūnas, Kęstutis

doi:10.1103/physreva.84.033812

Cited by 50 publications

(22 citation statements)

References 25 publications

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“…They are well-known due to their temporal dispersion and photonic band-gaps, but also for the spatial dispersion properties, allowing the management of spatial propagation properties of light. For particular geometries due to spatial dispersion modification PhCs may provide many interesting effects like spatial filtering [1][2][3], negative refraction [4], flat PhC lensing [5], collimation behind the PhC [6] and superlensing effect [7]. Most of these effects are due to reducing diffraction to zero, or due to negative diffraction.…”

Section: Indroductionmentioning

confidence: 97%

Focusing by a flat woodpile 3D photonic crystal

Maigytė

Cojocaru

Purlys

et al. 2013

2013 15th International Conference on Transparent Optical Networks (ICTON)

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We investigate spatial propagation effect behind the Photonic Crystal under particular dispersion conditions, which lead to a near field focusing. We analyze and experimentally demonstrate full two-dimensional near field focusing of light beams at visible frequencies behind the flat three-dimensional woodpile photonic crystal. Experimental results correspond well with numerical FDTD calculations as well as with the mode expansion studies. The focusing distance of 50 -70 µm behind the crystal is obtained. INDRODUCTIONPhotonic crystals (PhCs) are materials with spatially modulated refraction index on a wavelength scale. They are well-known due to their temporal dispersion and photonic band-gaps, but also for the spatial dispersion properties, allowing the management of spatial propagation properties of light. For particular geometries due to spatial dispersion modification PhCs may provide many interesting effects like spatial filtering [1-3], negative refraction [4], flat PhC lensing [5], collimation behind the PhC [6] and superlensing effect [7]. Most of these effects are due to reducing diffraction to zero, or due to negative diffraction. The negative diffraction inside PhC can be compensated by beam propagation in front and behind the crystal, which is the mechanism of flat-lens focusing, studied here.So far, most of studies of the flat lens focusing have been done with 2D PhCs, because they are less complicated to fabricate. However, to achieve full control over the beam propagation the 3D PhCs must be used. Some investigation of spatial effects with 3D modulated structures has been done, for example: self-collimation at visible frequencies in 3D PhCs [8,9], as well as at microwave frequencies [10] and in sound waves (sonic crystals) [11]. It is more easy to fabricate 3D structures for microwave and acoustic regimes as the high resolution for the structures is not required and they can be prepared by mechanical machining.In this work we concentrate on experimental demonstration of focusing by a 3D woodpile PhC. It's a first demonstration of full 2D focusing in the visible frequency regime, as even 1D focusing/imaging by PhC slabs has been so far experimentally demonstrated only in the near-infrared frequency range [12]. Full 2D focusing has been demonstrated experimentally in microwaves [13] and acoustics [14]. Moreover, we demonstrate FDTD simulations and calculations with simplified paraxial theory. We note a good agreement between experiment, theory and numerics. PARAXIAL APPROXIMATION, MODE EXPANSION and FDTDFigure 1: a) Illustration of the architecture of the woodpile PhC; b) Spatial dispersion curves of Bloch modes where the 'upper' branch shows convex segment (indicated by red arrow) which is the cause of focusing effect; c) Convex spatial dispersion surface in 3D.Negative spatial dispersion inside the PhC can compensate the diffractive broadening of the beams in free space in front and behind the PhC. For that reason we were looking for particular parameters of the PhC to obtain the negative dispersion...

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Section: Indroductionmentioning

confidence: 97%

Focusing by a flat woodpile 3D photonic crystal

Maigytė

Cojocaru

Purlys

et al. 2013

2013 15th International Conference on Transparent Optical Networks (ICTON)

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“…[15][16][17][19][20][21][22] Figure 1 shows images of the PhC patterns of different pitch, hence with different volume filling factor. Such woodpile structures are expected to have a reflectivity at wavelengths approximately twice the period.…”

Section: Experimental: Samples and Proceduresmentioning

confidence: 98%

Optical and thermal characterization on micro-optical elements made by femtosecond laser writing

et al. 2013

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Femtosecond laser polymerization of photonic crystals (PhCs) and diffractive micro-optical elements which can be easily integrated into complex 3D geometries of micro-fluidic chips is analysed in IR spectral domain. Thermal properties of such 3D optical elements and patterns were investigated by thermal imaging, IR spectroscopy and a heat-wave method using absorption-heating with visible light. Thermal imaging allows a simple in situ judgement on a 3D fabrication quality of photonic crystals and is simpler compared with scanning electron imaging. Photonic stop gaps at IR spectral range were clearly observed and IR mapping at the specific spectral wavelength reveals spatial uniformity of PhCs. Potential to use IR imaging with spectral IR plasmonic filters for sensor applications is discussed.

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“…[42][43][44][45][46][47][48][49][50] It should be mentioned that such structures can serve as 3D templates for infiltration of another media with desired properties which cannot be nanofabricated in 3D by DLW. [51][52][53] Lastly, usage of ultrashort pulses enables avoidance of photosensitization [54][55][56] which is an arising issue and might be limiting factor to optical and biological applications due to its light absorption and toxicity. Currently there are ultrashort pulsed DLW 3D lithography setups commercially available on the market by brand names Altechna R&D or Nanoscribe.…”

Section: Introductionmentioning

confidence: 99%

Employment of fluorescence for autofocusing in direct laser writing micro-/nano-lithography

2014

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Herein we present the implementation of autofocusing in multi-photon Direct Laser Writing (DLW) lithography. It is based on fluorescence occurring within the confined volume of a photopolymer/photoresin excitation resulting to a voxel generation. The proposed method is further successfully employed for the nanofabrication of large scale (500 nm in height, up to 25 mm 2 in area) Diffractive Optical Elements (DOE). The produced structures are characterized using Scanning Electron Microscope (SEM) and confocal optical profilometry. The introduced technique is potential for a simple, price and effort efficient upgrade of currently existing DLW micro-/nano-lithography setups.

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Formation of collimated beams behind the woodpile photonic crystal

Cited by 50 publications

References 25 publications

Focusing by a flat woodpile 3D photonic crystal

Focusing by a flat woodpile 3D photonic crystal

Optical and thermal characterization on micro-optical elements made by femtosecond laser writing

Employment of fluorescence for autofocusing in direct laser writing micro-/nano-lithography

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