Abstract:We introduce optically clear and resilient free-form micro-optical components of pure (non-photosensitized) organic-inorganic SZ2080 material made by femtosecond 3D laser lithography (3DLL). This is advantageous for rapid printing of 3D micro-/nano-optics, including their integration directly onto optical fibers. A systematic study of the fabrication peculiarities and quality of resultant structures is performed. Comparison of microlens resiliency to continuous wave (CW) and femtosecond pulsed exposure is determined. Experimental results prove that pure SZ2080 is ∼20 fold more resistant to high irradiance as compared with standard lithographic material (SU8) and can sustain up to 1.91 GW/cm 2 intensity. 3DLL is a promising manufacturing approach for high-intensity micro-optics for emerging fields in astro-photonics and atto-second pulse generation. Additionally, pyrolysis is employed to homogeneously shrink structures up to 40% by removing organic SZ2080 constituents. This opens a promising route towards downscaling photonic lattices and the creation of mechanically robust glass-ceramic microstructures.

An approach enabling nanoscale-additive manufacturing of inorganics based on phase transition via calcination of laser structured hybrid resin is proposed.

3D meso scale structures that can reach up to centimeters in overall size but retain micro-or nano-features, proved to be promising in various science fields ranging from micro-mechanical metamaterials to photonics and bio-medical scaffolds. In this work, we present synchronization of the linear and galvanometric scanners for efficient femtosecond 3D optical printing of objects at the meso-scale (from sub-µm to sub-cm spanning five orders of magnitude). In such configuration, the linear stages provide stitch-free structuring at nearly limitless (up to tens-of-cm) working area, while galvo-scanners allow achieving translation velocities in the range of mm/s-cm/s without sacrificing nano-scale positioning accuracy and preserving the undistorted shape of the final print. The principle behind this approach is demonstrated, proving its inherent advantages in comparison to separate use of only linear stages or scanners. The printing rate is calculated in terms of voxels/s, showcasing the capability to maintain an optimal feature size while increasing throughput. Full capabilities of this approach are demonstrated by fabricating structures that reach millimeters in size but still retain sub-µm features: scaffolds for cell growth, microlenses, and photonic crystals. All this is combined into a benchmark structure: a meso-butterfly. Provided results show that synchronization of two scan modes is crucial for the end goal of industrial-scale implementation of this technology and makes the laser printing well aligned with similar approaches in nanofabrication by electron and ion beams.

A pilot study on laser 3D printing of inorganic free-form micro-optics is experimentally validated. Ultrafast laser direct-write (LDW) nanolithography is employed for structuring hybrid organic-inorganic material SZ2080TM followed by high-temperature calcination post-processing. The combination allows the production of 3D architectures and the heat-treatment results in converting the material to inorganic substances. The produced miniature optical elements are characterized and their optical performance is demonstrated. Finally, the concept is validated for manufacturing compound optical components such as stacked lenses. This is an opening for new directions and applications of laser-made micro-optics under harsh conditions such as high intensity radiation, temperature, acidic environment, pressure variations, which include open space, astrophotonics, and remote sensing.

COMMUNICATIONand as self-organized nanopatterns induced on a surface, [ 30 ] are among other polarization-related phenomena demonstrated recently.The infl uence of beam polarization orientation on laser processing has been thoroughly studied in the cases of conductive and dielectric solid targets. [ 31,32 ] There are known effects of polarization on the scalar parameters of laser-matter interaction, such as absorption coeffi cient and ionization rate. [33][34][35][36] It is also known that heat conduction fl ux (vector) in plasma might be dependent on the direction of the imposed fi eld. [ 37 ] In what follows, these effects are considered in succession: (i) accumulation from multiple pulses, (ii) effects of polarization under high-numerical aperture (NA) focusing, and (iii) the infl uence of the external high-frequency electric fi eld on electronic heat conduction. The latter contribution has not yet been considered in laser fabrication under tight focusing. All these photomodifi cation mechanisms occur simultaneously and affect polymerization, which takes approximately a millisecond for common photoresists [ 38 ] at a >90% voxel overlap at typical writing velocity of 100 µm s -1 for widespread laser 3D nanolithography. [ 39 ] In this paper, a systematic analysis via modeling and experiments is presented in order to reveal polarization effects, their infl uence on the feature size (resolution), and the coupling between thermal gradient and polarization in DLW.To study and demonstrate the polarization effects, 3D suspended resolution bridges at various angles, α , between the linear polarization and scanning direction were fabricated on a glass substrate ( Figure 1 inset in (a); see details in the Experimental Section). The line-width difference was 10%-20% (varying exposure) under typical polymerization conditions for the linearly polarized pulses. The largest width of a 3D bridge was observed when the scan direction was perpendicular to the orientation of linear polarization, α = π / 2 ( E ⊥ v s ). The heightto-width ratio of the suspended lines was dependent on the orientation of linear polarization and changed between 3.07 and 3.44; self-focusing was not present under our experimental conditions. [ 40 ] Detailed analysis of polarization, threshold, and heat accumulation effects, which are all important, are discussed next.For the experimental conditions used, the focal spot diameter (at 1/ e 2 ) can be calculated as d f = 1.22 λ /NA = 898 nm assuming, for simplicity, a Gaussian intensity profi le. However, at such tight focusing it is necessary to use the vectorial Debye theory (specifi cs [ 41 ] can be found in Section A, Supporting Information), which predicts an ellipsoidal focal spot with two lateral cross sections: W l = 790 nm and W s = 572 nm for long and short cross sections, respectively (or 500 and 360 nm at full width at half maximum (FWHM)) for the actual experimental