100 GHz silicon–organic hybrid modulator

Electro-optic modulation at frequencies of 100 GHz and beyond is important for photonic-electronic signal processing at the highest speeds.To date,however,only a small number of devices exist that can operate up to this frequency.In this study,we demonstrate that this frequency range can be addressed by nanophotonic,silicon-based modulators.We exploit the ultrafast Pockels effect by using the silicon–organic hybrid(SOH)platform,which combines highly nonlinear organic molecules with silicon waveguides.Until now,the bandwidth of these devices was limited by the losses of the radiofrequency(RF)signal and the RC(resistor-capacitor)time constant of the silicon structure.The RF losses are overcome by using a device as short as 500 μm,and the RC time constant is decreased by using a highly conductive electron accumulation layer and an improved gate insulator.Using this method,we demonstrate for the first time an integrated silicon modulator with a 3dB bandwidth at an operating frequency beyond 100 GHz.Our results clearly indicate that the RC time constant is not a fundamental speed limitation of SOH devices at these frequencies.Our device has a voltage–length product of only V_(π)L=11 V mm,which compares favorably with the best silicon-photonic modulators available today.Using cladding materials with stronger nonlinearities,the voltage–length product is expected to improve by more than an order of magnitude.

Femtojoule electro-optic modulation using a silicon– organic hybrid device

Energy-efficient electro-optic modulators are at the heart of short-reach optical interconnects,and silicon photonics is considered the leading technology for realizing such devices.However,the performance of all-silicon devices is limited by intrinsic material properties.In particular,the absence of linear electro-optic effects in silicon renders the integration of energy-efficient photonic–electronic interfaces challenging.Silicon–organic hybrid(SOH)integration can overcome these limitations by combining nanophotonic silicon waveguides with organic cladding materials,thereby offering the prospect of designing optical properties by molecular engineering.In this paper,we demonstrate an SOH Mach–Zehnder modulator with unprecedented efficiency:the 1-mm-long device consumes only 0.7 fJ bit^(-1) to generate a 12.5 Gbit s^(-1) data stream with a bit-error ratio below the threshold for hard-decision forward-error correction.This power consumption represents the lowest value demonstrated for a non-resonant Mach–Zehnder modulator in any material system.It is enabled by a novel class of organic electro-optic materials that are designed for high chromophore density and enhanced molecular orientation.The device features an electro-optic coefficient of r33<180 pm V^(-1) and can be operated at data rates of up to 40 Gbit s^(-1).

Biophotonic sensors with integrated Si_(3)N_(4)-organic hybrid (SiNOH) lasers for point-of-care diagnostics

Early and efficient disease diagnosis with low-cost point-of-care devices is gaining importance for personalized medicine and public health protection.Within this context,waveguide-(WG)-based optical biosensors on the siliconnitride(Si_(3)N_(4))platform represent a particularly promising option,offering highly sensitive detection of indicative biomarkers in multiplexed sensor arrays operated by light in the visible-wavelength range.However,while passive Si_(3)N_(4)-based photonic circuits lend themselves to highly scalable mass production,the integration of low-cost light sources remains a challenge.In this paper,we demonstrate optical biosensors that combine Si_(3)N_(4)sensor circuits with hybrid on-chip organic lasers.These Si_(3)N_(4)-organic hybrid(SiNOH)lasers rely on a dye-doped cladding material that are deposited on top of a passive WG and that are optically pumped by an external light source.Fabrication of the devices is simple:The underlying Si_(3)N_(4)WGs are structured in a single lithography step,and the organic gain medium is subsequently applied by dispensing,spin-coating,or ink-jet printing processes.A highly parallel read-out of the optical sensor signals is accomplished with a simple camera.In our proof-of-concept experiment,we demonstrate the viability of the approach by detecting different concentrations of fibrinogen in phosphate-buffered saline solutions with a sensor-length(L-)-related sensitivity of S/L=0.16 rad nM^(-1)mm^(-1).To our knowledge,this is the first demonstration of an integrated optical circuit driven by a co-integrated low-cost organic light source.We expect that the versatility of the device concept,the simple operation principle,and the compatibility with cost-efficient mass production will make the concept a highly attractive option for applications in biophotonics and point-of-care diagnostics.

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.

3D-printed facet-attached microlenses for advanced photonic system assembly

Wafer-level mass production of photonic integrated circuits(PIC)has become a technological mainstay in the field of optics and photonics,enabling many novel and disrupting a wide range of existing applications.However,scalable photonic packaging and system assembly still represents a major challenge that often hinders commercial adoption of PIC-based solutions.Specifically,chip-to-chip and fiber-to-chip connections often rely on so-called active alignment techniques,where the coupling efficiency is continuously measured and optimized during the assembly process.This unavoidably leads to technically complex assembly processes and high cost,thereby eliminating most of the inherent scalability advantages of PIC-based solutions.In this paper,we demonstrate that 3D-printed facet-attached microlenses(FaML)can overcome this problem by opening an attractive path towards highly scalable photonic system assembly,relying entirely on passive assembly techniques based on industry-standard machine vision and/or simple mechanical stops.FaML can be printed with high precision to the facets of optical components using multi-photon lithography,thereby offering the possibility to shape the emitted beams by freely designed refractive or reflective surfaces.Specifically,the emitted beams can be collimated to a comparatively large diameter that is independent of the device-specific mode fields,thereby relaxing both axial and lateral alignment tolerances.Moreover,the FaML concept allows to insert discrete optical elements such as optical isolators into the free-space beam paths between PIC facets.We show the viability and the versatility of the scheme in a series of selected experiments of high technical relevance,comprising pluggable fiber-chip interfaces,the combination of PIC with discrete micro-optical elements such as polarization beam splitters,as well as coupling with ultra-low back-reflection based on non-planar beam paths that only comprise tilted optical surfaces.Based on our results,we believe that the FaML concept opens an attractive path towards novel PIC-based system architectures that combine the distinct advantages of different photonic integration platforms.

Ultra-broadband polarisation beam splitters and rotators based on 3D-printed waveguides

Multi-photon lithography has emerged as a powerful tool for photonic integration,allowing to complement planar photonic circuits by 3D-printed freeform structures such as waveguides or micro-optical elements.These structures can be fabricated with a high precision on the facets of optical devices and enable highly efficient package-level chip-chip connections in photonic assemblies.However,plain light transport and efficient coupling is far from exploiting the full geometrical design freedom offered by 3D laser lithography.Here,we extended the functionality of 3D-printed optical structures to manipulation of optical polarisation states.We demonstrate compact ultra-broadband polarisation beam splitters(PBSs)that can be combined with polarisation rotators and mode-field adapters into a monolithic 3D-printed structure,fabricated directly on the facets of optical devices.In a proof-of-concept experiment,we demonstrate measured polarisation extinction ratios beyond 11 dB over a bandwidth of 350 nm at near-infrared telecommunication wavelengths around 1550 nm.We demonstrate the viability of the device by receiving a 640 Gbit/s dual-polarisation data signal using 16-state quadrature amplitude modulation(16QAM),without any measurable optical-signal-to-noise-ratio penalty compared to a commercial PBS.