Scalable and controlled self-assembly of aluminum-based random plasmonic metasurfaces

Subwavelength metal-dielectric plasmonic metasurfaces enable light management beyond the diffraction limit.However,a costeffective and reliable fabrication method for such structures remains a major challenge hindering their full exploitation.Here,we propose a simple yet powerful manufacturing route for plasmonic metasurfaces based on a bottom-up approach.The fabricated metasurfaces consist of a dense distribution of randomly oriented nanoscale scatterers composed of aluminum(Al)nanohole-disk pairs,which exhibit angle-independent scattering that is tunable across the entire visible spectrum.The macroscopic response of the metasurfaces is controlled via the properties of an isolated Al nanohole-disk pair at the nanoscale.In addition,the optical field confinement at the scatterers and their random distribution of sizes result in a strongly enhanced Raman signal that enables broadly tunable excitation using a single substrate.This unique combination of a reliable and lithography-free methodology with the use of aluminum permits the exploitation of the full potential of random plasmonic metasurfaces for diagnostics and coloration.

Hybrid multi-chip assembly of optical communication engines by in situ 3D nanolithography

Three-dimensional(3D)nano-printing of freeform optical waveguides,also referred to as photonic wire bonding,allows for efficient coupling between photonic chips and can greatly simplify optical system assembly.As a key advantage,the shape and the trajectory of photonic wire bonds can be adapted to the mode-field profiles and the positions of the chips,thereby offering an attractive alternative to conventional optical assembly techniques that rely on technically complex and costly high-precision alignment.However,while the fundamental advantages of the photonic wire bonding concept have been shown in proof-of-concept experiments,it has so far been unclear whether the technique can also be leveraged for practically relevant use cases with stringent reproducibility and reliability requirements.In this paper,we demonstrate optical communication engines that rely on photonic wire bonding for connecting arrays of silicon photonic modulators to InP lasers and single-mode fibres.In a first experiment,we show an eight-channel transmitter offering an aggregate line rate of 448 Gbit/s by low-complexity intensity modulation.A second experiment is dedicated to a four-channel coherent transmitter,operating at a net data rate of 732.7 Gbit/s-a record for coherent silicon photonic transmitters with co-packaged lasers.Using dedicated test chips,we further demonstrate automated mass production of photonic wire bonds with insertion losses of(0.7±0.15)dB,and we show their resilience in environmental-stability tests and at high optical power.These results might form the basis for simplified assembly of advanced photonic multi-chip systems that combine the distinct advantages of different integration platforms.

Enhanced photoluminescence of a microporous quantum dot color conversion layer by inkjet printing

Owing to their high color purity,tunable bandgap,and high efficiency,quantum dots(QDs)have gained significant attention as color conversion materials for high-end display applications.Moreover,inkjet-printed QD pixels show great potential for realizing full-color mini/micro-light emitting diode(micro-LED)-based displays.As a color conversion layer,the photoluminescence intensity of QDs is limited by the insufficient absorptance of the excitation light due to the lack of scattering.Conventional scatterers,such as titanium dioxide microparticles,have been applied after additional surface engineering for sufficient dispersity to prevent nozzle clogging in inkjet printing process.In our work,as an alternative approach,we use inkjet printing for depositing a phase separating polymer ink based on polystyrene(PS)and polyethylene glycol(PEG).QD/polymer composite pixels with scattering micropores are realized.The morphology of the micropores can be tailored by the weight ratio between PS and PEG which enables the manipulation of scattering capability.With the presence of the microporous structure,the photoluminescence intensity of the QD film is enhanced by 110%in drop-cast films and by 35.3%in inkjet-printed QD pixel arrays compared to the reference samples.