We introduce a novel example of space-time analogy, where a dissipative soliton microcomb generates a traveling-wave temporal Fabry-Perot for trapping a bichromatic dispersive comb, generated at the second-harmonic of the pump laser. The fundamental frequency comb is generated in the anomalous dispersion regime, whereas the dispersive comb is generated in the normal dispersion regime. Direct numerical simulations are in excellent agreement with an analytical model.

This paper presents a novel sub-THz high-gain cascaded-lens antenna design approach that employs Gaussian beam propagation combined with low-cost dielectric materials and standard manufacturing techniques. The proposed lens antenna, solely designed based on a Gaussian beam model, achieves a maximum measured peak gain of 51.1 dBi across a broad sub-THz frequency range from 220 to 330 GHz, demonstrated for the first time, to the best of the authors’ knowledge. The antenna comprises a WR3.4 diagonal horn as the primary radiator and a cascaded pair of dielectric lenses, comprising a double-concave lens followed by a double-convex lens. This cascaded configuration effectively controls beam divergence, increases the effective aperture, and enables higher gain with a more compact horn-to-lens spacing than conventional single-lens designs. An analytical model based on Gaussian-beam propagation is developed to predict the antenna’s radiation characteristics, thereby reducing the need for time- and memory-intensive full-wave electromagnetic simulations in e.g., CST Microwave Studio Suite. The model’s accuracy is validated through comparison with both simulations and measurements for a single-lens configuration at 240 GHz, 280 GHz, and 320 GHz. The predicted results show excellent agreement with the measured radiation patterns and realized gain. For the cascaded-lens antenna, the theoretical and experimental peak-gain values agree closely across the entire operating band from 220 to 330 GHz. The proposed cascaded-lens antenna features a compact form factor, a high gain-to-aperture ratio of $\mathrm {13.01~mm ^{2}}$ , a low sidelobe level of −40 dBc, and an aperture efficiency of 66%. These results highlight the cascaded-lens approach as an efficient and scalable solution for next-generation sub-THz high-gain antenna systems.

The conversion between electrical and optical signals underpins modern optical communication systems and increasingly requires tight co-integration with electronics at short length scales. Photonic integrated circuits based on thin-film lithium tantalate has emerged as a promising electro-optic platform due to its large Pockels coefficient, low birefringence, low bias drift, and high power handling, yet its integration with standardized microelectronic processes remains limited. Here we show that incorporating the copper Damascene process into thin-film lithium tantalate modulators enables a scalable, electronics-compatible fabrication approach. The resulting devices exhibit approximately 10% lower microwave loss than conventional gold-electrode designs, while simultaneously supporting watt-level on-chip optical power handling and maintaining a stable quasi-static half-wave voltage from 1 Hz to 1 MHz, with a bias point drift of only 0.4 dB over a 15-hour period when operated at 1.75 mW on-chip optical power. High-speed transmission experiments demonstrate line rates of 416 Gbit/s (PAM4) and 540 Gbit/s (PAM8) below the 25% soft-decision forward-error-correction threshold. These results establish a practical route toward scalable chip-on-wafer integration of electro-optic modulators with microelectronic circuits.

We demonstrate a fully integrated photonic IMDD transmitter on a monolithic thin-film lithium tantalate platform, achieving an aggregate net data rate of 1.6 Tbit/s using wavelength-division multiplexing (WDM) with PAM-4 and PAM-8 modulation formats.

Thin-film lithium tantalate photonic integrated circuits have recently been demonstrated as a promising next-generation electro-optic platform, offering favorable properties including reduced DC drift, higher optical power handling, and lower birefringence compared to lithium niobate. However, high-speed LiTaO3 modulators reported to date have predominantly relied on silicon substrates, whose large dielectric constant compromises microwave velocity matching and imposes RF conductor losses that limit the achievable electro-optic bandwidth. Here, we implement a silicon substrate undercut technique to suspend the electrode region of lithium-tantalate-on-insulator (LTOI) Mach-Zehnder modulators (MZMs), effectively decoupling the traveling-wave electrodes from the high-permittivity silicon handle wafer, thereby reducing microwave losses. In addition, the undercut removes any susceptibility to parasitic surface conductance (PSC) induced losses of the oxide-silicon interface. The fabricated MZM achieves a 3 dB electro-optic bandwidth of 110 GHz, with a half-wave voltage of 5.1 V for an 8 mm-long device. Exploiting the extended bandwidth, we demonstrate a high single-lane intensity-modulation and direct-detection (IMDD) net data rate of 460 Gbit/s using PAM8 signaling. These results establish silicon substrate undercut as an effective and process-compatible pathway to unlock the full electro-optic potential of lithium tantalate on its native silicon-based wafer platform.

We report on the long-term optical performance of a two-photon polmerized microlens ring tip-tilt sensor. The study is backed by repeated measurements over the last six years, since the sensor was first tested in the sky at the Large Binocular Telescope. The goal of the study is to assess the feasibility of the underlying technology of two-photon polymerization for future instrumentation in the realistic environments experienced at astronomical telescopes.

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.

We demonstrate the lithium-tantalate-on-fused silica (LT-on-FS) Mach-Zehnder modulator manufactured in 4-inch wafer-scale. The modulator features a 3 dB electro-optic bandwidth of 67 GHz and a modulation efficiency of 1.6 V. We achieve net data rates of 437 Gbit/s with PAM8 signaling. © 2025 The Author(s)

Modern communication networks demand ever-increasing transmission bandwidth, placing stringent requirements on low-cost, high-performance electro-optic modulators. Substantial advances have been made in integrated photonics employing lithium niobate on insulator. In contrast, photonic integrated circuits based on lithium tantalate – a material already commercially adopted for wireless filters – have been developed, offering reduced DC drift, higher optical power handling, and lower birefringence. These advantages enable more complex and dense photonic integrated circuits, and make lithium tantalate a promising material platform for next-generation integrated electro-optic modulators. However, in contrast to the extensively studied thin-film lithium niobate platform, thin-film lithium tantalate modulators have only been explored on silicon substrates. Here, we report the first fabrication and characterization of thin-film lithium tantalate electro-optic modulators manufactured on a 4-inch (100 mm) fused-silica substrate for adapting a low-loss slow-wave microwave electrode to improve the electro-optic bandwidth. By employing a slow-wave electrode design to achieve velocity matching between microwave and optical signals, the demonstrated modulator achieves a 3-dB electro-optic bandwidth of 64 GHz with a low half-wave voltage of 1.53 V, with potential to operate at the measured 100 GHz electrical bandwidth, if the employed spectral biasing is removed. The modulator moreover exhibits low bias drift, with a constant switching voltage down to 10 mHz. This performance enables high-speed data transmission comparable to state-of-the-art lithium niobate modulators fabricated on quartz substrates. Using the fabricated devices, a net single lane data rate of 440.6 Gbps is achieved using PAM8 signaling.

Ultrabroadband integrated modulators involving materials beyond those available in silicon manufacturing increasingly rely on the Pockels effect. Among electro-optic materials, lithium tantalate offers comparable Pockels coefficients to lithium niobate but with significantly improved photostability, lower birefringence, higher optical damage threshold, and enhanced DC bias stability. Here we demonstrate wafer-scale heterogeneous integration of lithium tantalate films on low-loss silicon nitride photonic integrated circuits, achieving low optical losses ( ~ 14.2 dB/m) while combining the mature processing of silicon nitride waveguides with the ultrafast electro-optic response of thin-film lithium tantalate. The resulting devices achieve a 6 V half-wave voltage, and support modulation bandwidths of up to 100 GHz. We use single intensity modulators and in-phase/quadrature (IQ) modulators to transmit PAM4 and 16-QAM signals reaching up to 333 and 581 Gbit/s net data rates, respectively. Our results establish lithium tantalate-on-silicon nitride as a viable platform for RF photonics, interconnects, and analog signal processing.

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.

This paper presents the analysis of the inter-user interference (IUI) in a multiuser wireless link operating in the sub-THz frequency range of 270 GHz to 330 GHz. The link utilizes an optoelectronic transmitter (Tx) comprising two integrated external cavity lasers with a wide tuning range, a broadband electro-optic modulator, and a uni-traveling carrier photodiode with a WR3.4 output. A conformal lens-integrated WR3.4 frequency beam-steering antenna transmits the signal to seven users distributed in space. At the user side, an electronic sub-THz receiver is used for the wireless link. A finite portion of the Rx bandwidth (270 GHz to 330 GHz) is allocated to each user. The power ratio between the individual user channels is experimentally evaluated in three different test scenarios, operating at carrier frequencies of 290 GHz, 300 GHz, and 310 GHz, respectively. This evaluation is based on the frequency response analysis of the optoelectronic Tx, the electronic Rx, and the radiation characteristics of the frequency beam-steering antenna. To the best of our knowledge, this work presents the first IUI analysis in a sub-THz wireless link operating over a distance of 10 m, with a record high gross aggregated data rate of 140 Gbps across seven users. A worst-case power ratio of -2.5 dB between adjacent channels and an average power ratio of -11.3 dB is observed, highlighting the potential of sub-THz communication for high-data-rate multiuser networks.

This paper presents a novel sub-THz high-gain cascaded-lens antenna design approach that employs Gaussian beam propagation combined with low-cost dielectric materials and standard manufacturing techniques. The proposed lens antenna, solely designed based on a Gaussian beam model, achieves a maximum measured peak gain of 51.1 dBi across a broad sub-THz frequency range from 220 to 330 GHz, demonstrated for the first time, to the best of the authors' knowledge. The antenna comprises a WR3.4 diagonal horn as the primary radiator and a cascaded pair of dielectric lenses, comprising a double-concave lens followed by a double-convex lens. This cascaded configuration effectively controls beam divergence, increases the effective aperture, and enables higher gain with a more compact horn-to-lens spacing than conventional single-lens designs. An analytical model based on Gaussian-beam propagation is developed to predict the antenna's radiation characteristics, thereby reducing the need for time- and memory-intensive full-wave electromagnetic simulations in e.g., CST Microwave Studio Suite. The model's accuracy is validated through comparison with both simulations and measurements for a single-lens configuration at 240 GHz, 280 GHz, and 320 GHz. The predicted results show excellent agreement with the measured radiation patterns and realized gain. For the cascaded-lens antenna, the theoretical and experimental peak-gain values agree closely across the entire operating band from 220 to 330 GHz. The proposed cascaded-lens antenna features a compact form factor, a high gain-to-aperture ratio of 13.01 mm(-2) , a low sidelobe level of -40 dBc, and an aperture efficiency of 66%. These results highlight the cascaded-lens approach as an efficient and scalable solution for next-generation sub-THz high-gain antenna systems.

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.

In recent years, space-division multiplexing (SDM) has been proposed as a technique to cope with the increasing demand for higher per-fiber capacity in optical networks by modulating multiple independent signals onto multiple spatial paths. This can be accomplished by using specialized fibers that carry multiple signals in a number of fiber cores, fiber modes, or a combination of both types. In such fibers, strong spatial coupling of the signals requires for a joint digital signal processing (DSP) at the receiver. While research has mainly focused on system performance and multiple-input multiple-output (MIMO) equalizers, a reliable joint clock recovery tolerant to spatial-and-polarization-mode dispersion is an active field of research with recent progress. In this paper, we present a novel digital non-data-aided joint clock recovery that is tolerant to polarization-and-spatial-mode dispersion. The joint clock recovery is implemented in a feedforward architecture, which allows simple implementation. We provide a detailed analysis of the algorithm complexity for hardware implementation. In simulations, we show low clock phase jitter for fiber lengths up to 10,000$\,$km. Finally, we demonstrate clock recovery for a 90-GBd 16-QAM signal over a 150-km randomly-coupled 4-core fiber (RC-4CF) resulting in a total data rate of 2.88$\,$Tbit/s per wavelength and analyze equalizer convergence using a dedicated joint clock recovery.

We demonstrate the first high-speed lithium-tantalate-on-insulator (LTOI) Mach-Zehnder modulator (MZM) manufactured by highly scalable UV wafer-stepper lithography. 75 GHz 3-dB bandwidth electro-optical response and 528 Gbit/s line rates of P AM8 signaling is achieved. © 2024 The Author(s)

By incorporating additive manufacturing into the production of quasi-planar RF components, designers gain greater geometric freedom, enabling the fabrication of complex three-dimensional mmW components. The suitability of a standard 3D printing resin as substrate material is evaluated up to 220 GHz. To manufacture RF structures on this substrate, a combined laser structuring and wet etching process with an extremely low feature size and high dimensional accuracy is developed. The demonstrated 1 mm CPW lines show low losses of -2.3 dB at 220 GHz.

Driven by the prospects of higher bandwidths for optical interconnects, integrated modulators involving materials beyond those available in silicon manufacturing increasingly rely on the Pockels effect. For instance, wafer-scale bonding of lithium niobate films onto ultralow loss silicon nitride photonic integrated circuits provides heterogeneous integrated devices with low modulation voltages operating at higher speeds than silicon photonics. However, in spite of its excellent electro-optic modulation capabilities, lithium niobate suffers from drawbacks such as birefringence and long-term bias instability. Among other available electro-optic materials, lithium tantalate can overcome these shortcomings with its comparable electro-optic coefficient, significantly improved photostability, low birefringence, higher optical damage threshold, and enhanced DC bias stability. Here, we demonstrate wafer-scale heterogeneous integration of lithium tantalate films on low-loss silicon nitride photonic integrated circuits. With this hybrid platform, we implement modulators that combine the ultralow optical loss (∼ 14.2 dB/m), mature processing and wide transparency of silicon nitride waveguides with the ultrafast electro-optic response of thin-film lithium tantalate. The resulting devices achieve a 6 V half-wave voltage, and support modulation bandwidths of up to 100 GHz. We use single intensity modulators and in-phase/quadrature (IQ) modulators to transmit PAM4 and 16-QAM signals reaching up to 333 and 581 Gbit/second net data rates, respectively. Our results demonstrate that lithium tantalate is a viable approach to broadband photonics sustaining extended optical propagation, which can uniquely contribute to technologies such as RF photonics, interconnects, and analog signal processors.

This work describes the design process, manufacturing, and measurement of an antenna system consisting of an on-chip feeding element enhanced by 3D printed parasitic resonators operating around 246 GHz. The antennas are intended to be fed by the differential output of a wideband binary phase shift keying (BPSK) transmitter. The state-of-the-art is evaluated, and multiple possible complementary metal-oxide-metal (CMOS) back-end of line (BEOL) antenna structures are identified and compared against each other. The best option, in the form of a shorted bow-tie antenna, is selected. A parasitic resonator structure based on 3D printing and metallization is designed and improved using common mode analysis. The design and optimization process is detailed and explained. The realized designs are measured and compared against a similar concept using metallic resonators on a glass substrate as parasitic resonators. This is the first demonstration of a direct 3D printed structure on a CMOS antenna operating around 246 GHz.