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.

Photonic molecules with a tunable inter-cavity gap

Optical micro-resonators have broad applications.They are used,for example,to enhance light–matter interactions in optical sensors or as model systems for investigating fundamental physical mechanisms in cavity quantum electrodynamics.Coupling two or more micro-cavities is particularly interesting as it enlarges the design freedom and the field of application.In this context,achieving tunability of the coupling strength and hence the inter-cavity gap is of utmost importance for adjusting the properties of the coupled micro-resonator system.In this paper,we report on a novel coupling approach that allows highly precise tuning of the coupling gap of polymeric micro-resonators that are fabricated side by side on a common substrate.We structure goblet-shaped whispering-gallery-mode resonators on an elastic silicone-based polymer substrate by direct laser writing.The silicone substrate is mechanically stretched in order to exploit the lateral shrinkage to reduce the coupling gap.Incorporating a laser dye into the micro-resonators transforms the cavities into micro-lasers that can be pumped optically.We have investigated the lasing emission by micro-photoluminescence spectroscopy,focusing on the spatial localization of the modes.Our results demonstrate the formation of photonic molecules consisting of two or even three resonators,for which the coupling strengths and hence the lasing performance can be precisely tuned.Flexibility and tunability are key elements in future photonics,making our approach interesting for various photonic applications.For instance,as our coupling approach can also be extended to larger cavity arrays,it might serve as a platform for tunable coupled-resonator optical waveguide devices.