Three‐dimensional optical laser lithography beyond the diffraction limit

Abstract

Direct laser writing has become a versatile and routine tool for the mask-free fabrication of polymer structures with lateral linewidths down to less than 100 nm. In contrast to its planar counterpart, electron-beam lithography, direct laser writing also allows for the making of three-dimensional structures. However, its spatial resolution has been restricted by diffraction. Clearly, linewidths and resolutions on the scale of few tens of nanometers and below are highly desirable for various applications in nanotechnology. In visible-light far-field fluorescence microscopy, the concept of stimulated emission depletion (STED) introduced in 1994 has led to spectacular record resolutions down to 5.6 nm in 2009. This review addresses approaches aiming at translating this success in optical microscopy to optical lithography. After explaining basic principles and limitations, possible depletion mechanisms and recent lithography experiments by various groups are summarized. Today, Abbe's diffraction barrier as well as the generalized two-photon Sparrow criterion have been broken in far-field optical lithography. For further future progress in resolution, the development of novel tailored photoresists in combination with attractive laser sources is of utmost importance.

3D nano-architected metallic glass: Size effect suppresses catastrophic failure

“…We chose to work with sputter-deposited Zr-NiAl as the thin film metallic glass "coating" for the nanolattices based on this material's substantial tensile ductility at dimensions up to ~150 nm [11]. Nanolattices, or architected structural metamaterials, exhibit hierarchical ordering ranging from nanometer length scales in wall thickness to micron length scales in defining unit cells and beyond millimeter scales in the overall macroscale architecture, with many nano-architectures produced by using direct-laser-writing two-photon lithography [14][15][16][17]. Existing work on nanolattices has primarily focused on hollow ceramic nanolattices [18][19][20][21][22], due to the ease of depositing conformal coatings of ceramic materials by atomic layer deposition (ALD) and the M A N U S C R I P T 4 inertness of these ceramic materials to oxygen plasma, which has thus far been the plasma of choice for etching away the internal polymer scaffold to produce nanolattices.…”

Direct laser writing of three-dimensional network structures as templates for disordered photonic materials

“…Since the probability for two-photon absorption scales quadratically with laser intensity, the process is highly selective both laterally and axially, providing submicron resolution. The technique has been extended lately towards subdiffraction limited resolution [31], imitating the concept of stimulated emission depletion (STED) known from super-resolution scanning fluorescence microscopy [32,33].…”

Light polarization management via reflection from arrays of sub-wavelength metallic twisted bands

“…Single TB consisted of several rods, each rod having 1 × 0.3 µm cross section, which results from the two-photon laser writing with a tightly focused laser beam. These dimensions are limited by the polymerization threshold of the resist and the laser power [21]. Following the standard procedure of 3D laser writing [22], the structure was fabricated by photopolymerization of a liquid polymer photoresist (IP-L, Nanoscribe GmbH) on a microscope cover glass surface using a photolithographic workstation (Photonic Professional, Nanoscribe GmbH).…”