We report on the first demonstration of near-infrared dark-soliton Kerr microcombs in silicon microresonators. Leveraging reverse-biased p-i-n junctions to remove free carriers, our comb covers a spectral span exceeding 40 nm in the telecommunication C-band.

Previously, frequencies in the range f = (0.1.10) THz found mostly applications in molecular biology, medical imaging, security screening, and particle accelerators. Meanwhile, also terrestrial wireless THz communications has gained interest. The non-regulated frequency spectrum beyond 0.275 THz has atmospheric transmission windows with a power attenuation of 2 dB/km @ 0.2 THz, 5 dB/km @ 0.3 THz, 20 dB/km @ 0.4 THz, and 70 dB/km @ 0.9 THz. The unity-gain free-space propagation loss over a distance of L = 100 m amounts to a(dB) = 120 dB at lambda = 1 mm (f = 0.3 THz). In this case, and with a point-to-point link having an antenna gain of about 100 d(Bi), atmospheric losses are of secondary importance. To generate 16QAM signals at carrier frequencies f = 0.3 THz, we use optical-to-terahertz conversion by photomixing in a unitravelling-carrier photodiode (UTC). At the receiver side, a simple Schottky-barrier diode (SBD) directly detects the signal's intensity, from which the optical phase can be retrieved according to the Kramers-Kronig scheme. We demonstrate data transmission at a rate of 115 Gbit/s over a distance of 110 m, and we discuss the complexity of the Kramers-Kronig receiver. In a lecture-hall point-to-multipoint demonstration, we use a frequency-steered leaky-wave antenna, and transmit with 16QAM signaling a total of 80 Gbit/s over 16 m to a maximum number of four simultaneous users. For two users spaced 3.4 m apart, we transmit 40 Gbit/s per user. A monolithic microwave integrated circuit (MMIC) serves as the IQ receiver.

We successfully demonstrated a new WGM laser-based approach for detecting the HER2 cancer biomarker on extracellular vesicles (EVs), enabling accurate quantification that outperforms the current gold standard in sensitivity.

Kerr soliton microcombs have the potential to disrupt a variety of applications such as ultra-high-speed optical communications, ultra-fast distance measurements, massively parallel light detection and ranging (LiDAR) or high-resolution optical spectroscopy. Similarly, ultra-broadband photonic-electronic signal processing could also benefit from chip-scale frequency comb sources that offer wideband optical emission along with ultra-low phase noise and timing jitter. However, while photonic analogue-to-digital converters (ADC) based on femtosecond lasers have been shown to overcome the jitter-related limitations of electronic oscillators, the potential of Kerr combs in photonic-electronic signal processing remains to be explored. In this work, we demonstrate a microcomb-based photonic-electronic ADC that combines a high-speed electro-optic modulator with a Kerr comb for spectrally sliced coherent detection of the generated optical waveform. The system offers a record-high acquisition bandwidth of 320 GHz, corresponding to an effective sampling rate of at least 640 GSa/s. In a proof-of-concept experiment, we demonstrate the viability of the concept by acquiring a broadband analogue data signal comprising different channels with centre frequencies between 24 GHz and 264 GHz, offering bit error ratios (BER) below widely used forward-error-correction (FEC) thresholds. To the best of our knowledge, this is the first demonstration of a microcomb-based ADC, leading to the largest acquisition bandwidth demonstrated for any ADC so far.

To sustain the persistent traffic growth in optical networks, symbol rates are continuously increasing, in particular in long-haul and submarine systems, where efficient exploitation of the installed fiber infrastructure is key. However, while commercial long-haul transceivers already offer symbol rates of 200 GBd, exploring the potential of transmission at symbol rates beyond this landmark still represents a challenge. One of the main difficulties is to reliably generate and analyze high-quality quadrature amplitude modulation (QAM) signals at bandwidths of more than 200 GHz, exceeding the capabilities of available test and measurement instrumentation. In this paper, we demonstrate the potential of high-symbol-rate transmission at 300 GBd over trans-oceanic distances, exploiting the concepts of optical arbitrary waveform generation (OAWG) and optical arbitrary waveform measurement (OAWM) for synthesizing and analyzing the associated data signals. Using dual-polarization probabilistic-constellation-shaped (PCS) 36QAM signals, we achieve net bit rates of 2.45 Tbit/s over 1 815 km. For PCS-16QAM signals, the transmission distance is extended to 9 680 km while supporting a net bit rate of 1.63 Tbit/s. In the back-to-back setup, the net bit rate is increased to 2.88 Tbit/s using 64QAM signals. To the best of our knowledge, our experiments achieve the highest symbol rate so far transmitted over a distance exceeding 100 km. Furthermore, the demonstrated distances for target net bit rates of 1.6 Tbit/s and 2.4 Tbit/s surpass previous demonstrations by more than an order of magnitude.

We demonstrate an optically packaged silicon-organic hybrid (SOH) Mach-Zehnder modulator operating at PAM4 data rates of up to 112 Gbit/s. The device is directly driven by a CMOS SerDes chip without additional optical or RF amplifiers.

Generation of electrical waveforms with bandwidths of 100 GHz or more is key to many applications in science and industry, comprising high-speed communications, radar, or test and measurement equipment. However, while conventional digital-to-analog converters based on electronic circuits still represent the technological mainstay for broadband waveform generation, further bandwidth scaling comes with a series of challenges related to circuit design and implementation, packaging, and system integration. In this paper, we show that photonic-electronic signal-processing techniques may overcome these limitations. We demonstrate a photonic-electronic waveform generator that exploits quadrature multiplexing in the optical domain in combination with phase-stabilized coherent down-conversion to the electrical domain. In a proof-of-concept experiment, we generate electrical multi-level data signals at symbol rates up to 200 GBd at quality levels that can already compete with best-in-class electronic systems. We believe that our concept opens an attractive path to waveforms generation at bandwidths beyond the limitations of current microelectronics, leveraging advanced photonic integration technologies that are currently being developed.

We leverage dark-soliton microcombs to demonstrate optical arbitrary waveform generation (OAWG) at unprecedented bandwidths of more than 400 GHz. We use the scheme for 16QAM and 32QAM transmission at 400 GBd - a record-high symbol rate for fully coherent QAM signalling. (c) 2025 The Author(s)

Electro-optic modulators are key for advanced functionalities of photonic integrated circuits (PIC) which are preferably fabricated on silicon using CMOS processing. However, silicon lacks a second-order nonlinear susceptibility (Pockels effect), and this prevents a native implementation of modulators. This deficiency can be overcome when employing the plasma dispersion effect by injecting or depleting carriers in a waveguide section. It is technically more favourable to complement silicon with a Pockels-type organic electro-optic material which fills the slot of a silicon slot waveguide. An applied voltage then changes the refractive index and thereby the phase of a propagating optical slot mode. Such siliconorganic hybrid (SOH) phase shifters form the arms of a Mach-Zehnder modulator (MZM). We discuss the design of SOH MZM, define performance metrics for comparing different modulator realizations, and address strategies for the long-term stability of the organic material. Besides providing data for modulators used in the area of communications, we also refer to an unconventional application, namely to the optical read-out of cryoelectronic circuits.

The conventional way of generating optical waveforms relies on in-phase and quadrature (IQ) modulation of a continuous-wave (CW) laser tone. In this case, the bandwidth of the resulting optical waveform is limited by the underlying electronic components, in particular by the digital-to-analog converters (DACs) generating the drive signals for the IQ modulator. This bandwidth bottleneck can be overcome by using a concept known as optical arbitrary waveform generation (OAWG), where multiple IQ modulators and DACs are operated in parallel to first synthesize individual spectral slices, which are subsequently combined to form a single ultra-broadband arbitrary optical waveform. However, targeted synthesis of arbitrary optical waveforms from multiple spectral slices has so far been hampered by difficulties to maintain the correct optical phase relationship between the slices. In this paper, we propose and demonstrate spectrally sliced OAWG with active phase stabilization, which permits targeted synthesis of truly arbitrary optical waveforms. We demonstrate the viability of the scheme by synthesizing optical waveforms with record-high bandwidths of up to 325 GHz from four individually generated optical tributaries. In a proof-of-concept experiment, we use the OAWG system to generate 32QAM data signals at symbol rates of up to 320 GBd, which we transmit over 87 km of single-mode fiber and receive by a two-channel non-sliced optical arbitrary waveform measurement (OAWM) system, achieving excellent signal quality. We believe that our scheme can unlock the full potential of OAWG and disrupt a wide range of applications in high-speed optical communications, photonic-electronic digital-to-analog conversion, as well as advanced test and measurement in science and industry.

We demonstrate PAM4, PAM6, and PAM8 signaling using a 280 µm-long SOH Mach-Zehnder modu-lator (MZM). We achieve PAM4 symbol rates of 204 GBd and PAM8 line rates of 528 Gbit/s (412.5 Gbit/s net data rate) – record-high values for devices on the silicon photonic platform.

We demonstrate a homodyne cryogenic optical egress link utilizing a silicon-organic hybrid (SOH) phase modulator. With our approach, we achieve a record-low total net energy dissipation of less than 10 fJ/bit per net bit at a temperature of 3.6 K and a data rate of 40 Gbit/s. (c) 2025 The Author(s)

We demonstrate piezo-tunable hybrid integrated lasers offering linewidths below 100 Hz along with highly linear and fast frequency tuning. For a tuning range of 1 GHz, residual nonlinearities are below 0.07 %, allowing for 5 cm ranging precision in an FMCW LiDAR demonstration.

Silicon-organic hybrid (SOH) integration can complement intrinsically scalable silicon photonic circuits by novel functionalities, obtained through theory-guided material engineering. This presentation will give an overview of our recent progress in exploring the potential of the SOH platform and in bringing the technology from laboratory demonstrations to industrial applications. Full-text article not available; see video presentation

Silicon photonic integrated circuits comprising electro-optic modulators are key to a broad spectrum of applications. However, while the silicon photonics platform takes advantage of the well-established complementary metal-oxide-semiconductor (CMOS) processing technology for fabricating silicon-on-insulator (SOI) waveguides with high reproducibility, crystalline silicon lacks a second-order nonlinear susceptibility, which limits the functionality of the entire integration platform. The plasma dispersion effect provides an alternative means to change the refractive index by injection or depletion of carriers, but this approach has some disadvantages with respect to speed, efficiency, and footprint. Complementing silicon with Pockels-type organic electro-optic materials (silicon-organic hybrid, SOH) can overcome these limitations. In this review, we describe state-of-the-art organic electro-optic materials, address promising strategies to resolve stability concerns, discuss fabrication technologies, and we elaborate on the design of SOH Mach-Zehnder modulators (MZM). Our discussion on performance and applications of SOH MZM starts with the definition of metrics by which various modulator realizations can be compared. Beyond the standard use of SOH MZM, we draw attention to unconventional applications like optical read-out of cryoelectronic circuits and other emerging areas in metrology and sensing which are so far not in the primary focus of the community.

We exploit high-resolution multi-photon lithography for fabricating 3D-freeform millimeter-wave and THz structures that overcome the limitations of conventional planar architectures. We demonstrate THz probes, suspended antennas, and ultra-broadband chip-chip interconnects offering bandwidths in excess of 0.3 THz.

We demonstrate an optically and electrically packaged silicon photonic receiver system for non-sliced optical arbitrary waveform measurement (OAWM). The OAWM engine is used for high-speed data transmission and for photonic-electronic analog-to-digital conversion at bandwidths of up to 320 GHz.

Direct-write multi-photon laser lithography (MPL) combines highest resolution on the nanoscale with essentially unlimited 3D design freedom. Over the previous years, the groundbreaking potential of this technique has been demonstrated in various application fields, including micromechanics, material sciences, microfluidics, life sciences as well as photonics, where in-situ printed optical coupling elements offer new perspectives for package-level system integration. However, millimeter-wave (mmW) and terahertz (THz) devices could not yet leverage the unique strengths of MPL, even though the underlying devices and structures could also greatly benefit from 3D freeform microfabrication. One of the key challenges in this context is the fact that functional mmW and THz structures require materials with high electrical conductivity and low dielectric losses, which are not amenable to structuring by multi-photon polymerization. In this work, we introduce and experimentally demonstrate a novel approach that allows to leverage MPL for fabricating high-performance mmW and THz structures with hitherto unachieved functionalities. Our concept exploits in-situ printed polymer templates that are selectively coated through highly directive metal deposition techniques in combination with precisely aligned 3D-printed shadowing structures. The resulting metal-coated freeform structures offer high surface quality in combination with low dielectric losses and conductivities comparable to bulk material values, while lending themselves to fabrication on planar mmW/THz circuits. We experimentally show the viability of our concept by demonstrating a series of functional THz structures such as THz interconnects, probe tips, and suspended antennas. We believe that our approach offers disruptive potential in the field of mmW and THz technology and may unlock an entirely new realm of laser-based 3D manufacturing.

An efficient numerical algorithm is developed to model wave propagation in 3D-printed freeform waveguides, so-called photonic wire bonds (PWBs). The method utilizes transformation-optics (TO) in combination with curvilinear meshing to transform the original 3D-freeform PWB into a straight waveguide with anisotropic material properties. This waveguide is then modeled using an anisotropic full-vectorial beam propagation method (BPM). We demonstrate the viability of our TO-BPM algorithm and benchmark its performance against a finite-difference-time-domain (FDTD) method. Our approach shows a 600-fold reduction of the computation time in combination with a mean percentage error of 3.2