Erbium-doped fiber amplifiers revolutionized long-haul optical communications and laser technology. Erbium ions could provide a basis for efficient optical amplification in photonic integrated circuits but their use remains impractical as a result of insufficient output power. We demonstrate a photonic integrated circuit–based erbium amplifier reaching 145 milliwatts of output power and more than 30 decibels of small-signal gain—on par with commercial fiber amplifiers and surpassing state-of-the-art III-V heterogeneously integrated semiconductor amplifiers. We apply ion implantation to ultralow–loss silicon nitride (Si 3 N 4 ) photonic integrated circuits, which are able to increase the soliton microcomb output power by 100 times, achieving power requirements for low-noise photonic microwave generation and wavelength-division multiplexing optical communications. Endowing Si 3 N 4 photonic integrated circuits with gain enables the miniaturization of various fiber-based devices such as high–pulse-energy femtosecond mode-locked lasers.

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We study the molecular structure of one monolayer of picene on a Ag(100) surface. Low energy electron diffraction and scanning tunneling microscopy experiments show that the molecules arrange in a highly ordered manner exhibiting a point-on-line epitaxy with two differently arranged molecules per unit cell. Comparing measured and simulated photoelectron momentum maps allows further conclusions about the composition of the unit cell. The structural basis consists of two parallel molecules; one molecule lies face-on and the other is tilted by ≈45° around its long axis with respect to the surface normal.

Active optical metasurfaces with dynamic switchable, tunable, and reconfigurable optical functionalities are an emerging field in photonics and optoelectronics. Especially, chalcogenide-based phase-change materials, such as Ge2Sb2Te5 (GST), can be fast and repeatedly switched by external stimuli between crystalline and amorphous states, typically accompanied by a tremendous difference of the electronic and photonic properties. Here, we demonstrate that focused ion beam-induced disorder in highly confined regions can transform phase-change materials in active optical metasurfaces by locally adjusting the phase. A careful control of the amount of disorder can locally tailor the effective refractive index in GST films on the nanometer scale, which is highly promising for multilevel switching applications. In contrast to direct laser writing, focused ion beam irradiation enables the fabrication of subwavelength-scaled, planar, nonvolatile, and reconfigurable optical metasurfaces, with pattern sizes clearly below the diffraction limit of common laser light sources.