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Low noise, high power single-frequency lasers and amplifiers are key components of interferometric gravitational wave detectors. One way to increase the detector sensitivity is to increase the power injected into the interferometers. We developed a fiber amplifier engineering prototype with a pump power limited output power of 200 W at 1064 nm. No signs of stimulated Brillouin scattering are observed at 200 W. At the maximum output power the polarization extinction ratio is above 19 dB and the fractional power in the fundamental transverse mode (TEM 00) was measured to be 94.8 %. In addition, measurements of the frequency noise, relative power noise, and relative pointing noise were performed and demonstrate excellent low noise properties over the entire output power slope. In the context of single-frequency fiber amplifiers, the measured relative pointing noise below 100 Hz and the higher order mode content is, to the best of our knowledge, at 200 W the lowest ever measured. A long-term test of more than 695 h demonstrated stable operation without beam quality degradation. It is also the longest single-frequency fiber amplifier operation at 200 W ever reported.

In this paper, approaches for the realization of high-resolution periodic structures with gap sizes at sub-100 nm scale by two-photon polymerization (2PP) are presented. The impact of laser intensity on the feature sizes and surface quality is investigated. The influence of different photosensitive materials on the structure formation is compared. Based on the elliptical geometry character of the voxel, the authors present an idea to realize high-resolution structures with feature sizes less than 100 nm by controlling the laser focus position with respect to the glass substrate. This investigation covers structures fabricated respectively in the plane along and perpendicular to the major axis of voxel. The authors also provide a useful approach to manage the fabrication of proposed periodic structure with a periodic distance of 200 nm and a gap size of 65 nm.

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Abstract-Optical interconnects are the key components for integrated optics to link photonic integrated circuits or to connect external elements such as light sources and detectors. However, misalignment of the optical elements contained and its compensation is a remaining challenge for integrated optical devices. We present a novel method to establish rigid interconnects based on a 2-wavelength self-written waveguide process which automatically compensates for misalignment. We exemplarily demonstrate the capability of our process by writing interconnects between two multimode fibers as well as hot-embossed integrated polymer waveguides and a bare laser diode chip. The coupling efficiency of the interconnects obtained is analyzed with respect to misalignment. We found that coupling losses are as low as 1.3 dB if a lateral misalignment lies within a 10 µm interval, which is achieved by commercially available pick-and-place machines. Our approach is easily combined with high-throughput techniques such as hot embossing and enables low-cost production of interconnects even for mass fabrication in future applications.

Optical waveguides were fabricated on flexible foil substrates by ink-jet printing, to complement and enhance printed flexible electronics with optical networks. The 145 μm wide and 20 μm high transparent polymer tracks were created by printing subsequent tracks of an acrylate ink on polymer foil. A printable, optically transparent material was prepared by a combination of an acrylate resin with a low-viscosity, co-polymerising acrylate. This solved the problem of solvent evaporation for substrates with low heat tolerance. Thermally induced pinning, used to prevent the ink from spreading out on the substrate was achieved by heating the substrate to 60 °C, and found to be strongly affected by the time lapse between deposition of the individual layers. This tool allowed to increase the aspect ratio of the printed tracks from 0.07 to 0.17, and the contact angle of the printed tracks from 15°to 37°. After completion of the deposition step, the waveguides were polymerised under UV light, and covered by a printed upper cladding layer. In the optical evaluation, transmission could be demonstrated with an attenuation in the range of 1.4 dB cm −1 for a wavelength of 785 nm, with a significant portion of material attenuation.

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