Refractive index measurements of photo-resists for three-dimensional direct laser writing

Gissibl, Timo; Wagner, Sebastian; Sýkora, Jáchym; Schmid, M.; Gießen, Harald

doi:10.1364/ome.7.002293

Cited by 134 publications

(79 citation statements)

References 14 publications

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“…While microspheres reported in literature have generally demonstrated values of >10 3 , traditionally microspheres reported in literature are much larger, herein our microspheres have a diameter of only 3.6 µm, the smaller the microsphere the larger the optical losses . In addition, the composition of the microsphere is silica with a refractive index of 1.46, the template in which the microsphere is embedded has a refractive index of 1.52, that could also result in some leakage/scattering losses at points where the microsphere is in contact with the template. Comparatively, Kushida et al studied conjugated polymer microspheres with similar sizes to what is being studied herein, one major difference was the refractive index for their polymer was significantly higher ( n = 1.8–2.0).…”

Section: Introductionmentioning

confidence: 76%

Coupled Whispering Gallery Mode Resonators via Template‐Assisted Assembly of Photoluminescent Microspheres

Smith

Zeng

Lafalce

et al. 2019

Adv Funct Materials

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This study reports a facile method for the assembly of large, array style, coupled dye-doped microsphere resonators by template-assisted, in which an aqueous suspension of colloidal microspheres assemble on a patterned template. By exploiting the high resolution of 3D (two-photon) lithography derived templates, closely packed large arrays, hundreds to thousands of dimers with controlled gap spacing, only limited by the size of the substrate can be achieved. Dye-doped emissive microspheres with Q-factors >2.5 × 10 2 can be achieved and trapped into predetermined cavity positions, thereby controlling the distance between adjacent microspheres. This design allows to scale down dimer spacing from usual 400 nm for traditional photolithography to very small spacing of 50 nm. It is found that exciting individual microspheres in the ensemble shows intense optical cavity modes, whereas closely coupled pairs show controlled mode splitting. Coupling between photoluminescent microspheres is strongly influenced by the gap distance, with strong coupling, equating to normal mode splitting, arising as the gap distance is reduced below traditional sub-micrometer scale. The coupled dimer assemblies are promising candidates for advancing the development of largearea coupled nanophotonic structures, beyond the spatial resolution-limited photolithographical derived arrays.

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Section: Introductionmentioning

confidence: 76%

Coupled Whispering Gallery Mode Resonators via Template‐Assisted Assembly of Photoluminescent Microspheres

Smith

Zeng

Lafalce

et al. 2019

Adv Funct Materials

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“…For the polymer and the laminate metamaterial refractive indices, Cauchy's equation was used with parameters as determined for the photoresist IP‐L (Nanoscribe GmbH, Germany) in refs. and , respectively.…”

Section: Methodsmentioning

confidence: 98%

“…To connect to our experiments, we search for Bragg‐diffracted eigenmodes with k x = k y = N 2π/ a and integer N . The refractive index of the polymer, the photonic crystal is made of, is n polymer = 1.51 . We fix the ellipticity of the polymer rods (compare Figure ) typical for 3D direct laser writing to the ratio of rod semiaxes r z / r x = 2.5, with r x = r y .…”

mentioning

confidence: 99%

Second‐Harmonic Generation by 3D Laminate Metacrystals

Wickberg

Abass

Hsiao

et al. 2019

Advanced Optical Materials

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generation (SHG) or large linear electrooptic coefficients. [5][6][7][8] The entries of the second-order nonlinear optical susceptibility tensor have become comparable to and even larger than those of established crystalline materials such as KDP (monopotassium phosphate). [9] In sharp contrast to such crystals, laminate metamaterials can be deposited conformally onto any kind of amorphous surface by atomiclayer deposition (ALD), enabling the integration into various systems. [10] In this Communication, we investigate the possibility of enhancing the secondorder frequency-conversion efficiency by bringing together the ideas of 3D dielectric photonic crystals and dielectric laminate metamaterials. Due to their hybrid nature, we refer to these structures as "3D laminate metacrystals" (see Figure 1a).An obvious advantage of this hybrid approach is based on the fact that ALD is a conformal process. Therefore, the overall amount of material grown after some time in a structure with N inner surfaces is N-times larger than that grown on a single planar surface during the same time. This is a relevant aspect, because ALD does not allow for growing films with thicknesses of tens of micrometers on planar surfaces within reasonable time. Originally, we anticipated two further advantages of this hybrid approach: nonlinear optical phase matching by the dispersion relation of photonic crystals and enhanced nonlinearities by small group velocities ("slow light") near the extrema of photonic bands. [11][12][13][14][15][16][17] However, these aspects turned out to be of minor importance for the understanding of the resonances observed in this report.The samples have been fabricated as follows. We start by manufacturing 3D woodpile polymer templates on glass substrate by using a home-built setup for 3D direct laser writing. [18,19] Ordinarily, one uses photoinitiator molecules in a monomer to support efficient two-photon absorption required in the direct laser writing process. [20] However, the photoinitiator molecules lead to two-photon-induced fluorescence in the final structures. This fluorescence can largely obscure the SHG measurements. Therefore, we use an acrylate resist without any additional photoinitiator and directly excite optical transitions in the monomer by tightly focused femtosecond laser pulses centered at 405 nm wavelength (see the Experimental Section for further details). Despite the absence of a photoinitiator, we will still report on remaining polymer autofluorescence below.We have varied the rod spacing, a, the axial lattice constant, c, and the rod cross section of the resulting woodpile photonic crystals. A ratio of = / 2 c a leads to a face-centered cubic diamond-like lattice, a ratio of c/a = 1 to a body-centered cubic 3D dielectric woodpile photonic crystals, which are conformally coated with locally noninversion-symmetric dielectric laminate metamaterials, are discussed. These "3D laminate metacrystals" are fabricated by 3D direct laser writing of an acrylate without photoinitiator to reduce two-photo...

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“…The laser beam is focused by a 63× objective through immersion oil and glass substrate into the photoresist (IP‐L 780, Nanoscribe). After polymerization the photoresist has a refractive index of around n = 1.51 at 780 nm . To improve the adhesion of the woodpile structures, the glass substrates are silanized prior to dropcasting the photoresist.…”

Section: Methodsmentioning

confidence: 99%

Polarization Conversion Effect in Biological and Synthetic Photonic Diamond Structures

Rodríguez-Gallegos

Heep

et al. 2018

Advanced Optical Materials

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Polarization of light is essential for some living organisms and many optical applications. Here, an orientation dependent polarization conversion effect is reported for light reflected from diamond‐structure‐based photonic crystals (D‐structure) inside the scales of a beetle, the weevil Entimus imperialis. When linearly polarized light propagates along its 〈100〉 directions, the D‐structure behaves analogous to a half‐wave plate in reflection but based on a different mechanism. The D‐structure rotates the polarization direction of linearly polarized light, and reflects circularly polarized light of both handednesses without changing it. This polarization effect is different from circular dichroism occurring in chiral biological photonic structures discovered before. The structural origin of this effect is symmetry breaking inside D‐structure's unit cell. This finding demonstrates that natural photonic structures can exploit multiple functionalities inherent to the design principles of their structural organization. Aiming at transferring the inherent polarization effect of the biological D‐structure to technically realizable materials, three simplified biomimetic structural models are derived and it is theoretically demonstrated that they retain the effect. Out of these structures, functioning woodpile structure prototypes are fabricated.

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Refractive index measurements of photo-resists for three-dimensional direct laser writing

Cited by 134 publications

References 14 publications

Coupled Whispering Gallery Mode Resonators via Template‐Assisted Assembly of Photoluminescent Microspheres

Coupled Whispering Gallery Mode Resonators via Template‐Assisted Assembly of Photoluminescent Microspheres

Second‐Harmonic Generation by 3D Laminate Metacrystals

Polarization Conversion Effect in Biological and Synthetic Photonic Diamond Structures

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