This letter describes an approach for recording three-dimensional (3D) periodic structures in a photosensitive polymer using a single diffraction element mask. The mask has a central opening surrounded by three diffraction gratings oriented $\text{120°}$ relative to one another such that the three first order diffracted beams and the nondiffracted laser beam give a 3D spatial light intensity pattern. Structures patterned in this polymer using 1.0 and 0.56 μm grating periods have hexagonal symmetry with micron- to submicron-periodicity over large substrate area. Band structure calculations of these low index contrast materials predict photonic gaps in certain high symmetry directions.

Antiresonant hollow-core fibers (AR-HCFs) have opened up exciting possibilities for high-energy and high-power laser delivery because of their exceptionally low nonlinearities and high damage thresholds. While these fiber designs offer great potential for handling kilowatt-class powers, it is crucial to investigate their performance at multi-kW power levels. Until now, transmission of narrow-linewidth single-mode lasers at multi-kW power levels through a HCF has not been demonstrated, to our knowledge. Here, we present the delivery of a record 2.2 kW laser power with an input spectral linewidth of 86 GHz, centered at 1080 nm, while maintaining 95% transmission efficiency and beam quality (M²) of 1.03. This was achieved via a 104.5 m single-mode five-tube nested AR-HCF with 0.79 dB/km loss. Furthermore, we show power delivery of 1.7 kW with a spectral linewidth as narrow as 38 GHz through the same fiber. Our results could lead to a new generation of fiber-based laser beam delivery systems with applications in precision machining, nonlinear science, directed energy, and power beaming over fiber.

This letter describes a simple synthetic approach to fabricate two-dimensional midinfrared CdSe photonic crystals (PC) by electrodeposition of CdSe in a polymer template defined using interference lithography. Characterization of the transmission spectra of CdSe PCs with a hexagonal array of 1.3 μm diameter and 2.7 μm pitch air voids showed a well-defined drop in transmission at 4.23 μm. The drop in transmission increased with incident angle, reaching a maximum of approximately 2.6 dB at 40° relative to the surface normal. This two-step synthetic approach can be used to incorporate photonic crystals onto arbitrary substrates for integration into future advanced optical circuits.

Surface plasmon excitation using resonant metal nanoparticles is studied experimentally. Geometry dependent reflection measurements reveal the existence of several optical resonances. Strong coupling of the in-plane nanoparticle plasmon resonance and propagating plasmons is evident from clear anticrossing behavior. Reflection measurements at high numerical aperture demonstrate the excitation of surface plasmons via out-of-plane particle polarization. The thus excited plasmons do not exhibit anticrossing in the considered frequency range. The results are explained in terms of the known surface plasmon dispersion relation and the anisotropic frequency dependent nanoparticle polarizability. These findings are important for applications utilizing surface-coupled nanoparticle plasmon resonances.

We have introduced line defects into a three-dimensional (3D) photonic crystal by combining the techniques of optical photolithography, self-assembly, and template replication. The template is a colloidal crystal film that is grown on a silicon or glass substrate patterned with photoresist lines, and the 3D photonic crystal with air-core line defects is obtained by infiltrating the colloidal crystal film with silica and removing the template by calcination. SEM and optical transmission spectra show that the resulting 3D PC structure has high structural integrity and crystalline quality. This approach can introduce defects at the desired places of 3D photonic crystals, which may be useful in making 3D photonic crystal-based air-core waveguides.