arXiv subjects

Camiel Op de Beeck

Publications and source records attributed to Camiel Op de Beeck.

5 recordsLinked to original sources

arXiv2026

$f$-2$f$ self-referencing for silicon nitride photonics via a heterogeneously integrated lithium niobate layer

Heterogeneous integration combines complementary material properties in a single photonic platform. Here, we demonstrate on-chip $f$-2$f$ self-referencing in a heterogeneously integrated Si$_3$N$_4$/LiNbO$_3$ platform, in which supercontinuum generation in a Si$_3$N$_4$ waveguide and second-harmonic generation in a LiNbO$_3$ layer are spatially separated and linked by adiabatic escalator couplers. Pumped by a 1560 nm mode-locked laser with 75 pJ on-chip pulse energy, we detect the carrier-envelope offset frequency with 30 dB signal-to-noise ratio in 300 kHz resolution bandwidth. A comparative measurement confirms that the second harmonic originates in the LiNbO$_3$ layer and indicates opportunity for further improvements through periodic poling. These results establish heterogeneous Si$_3$N$_4$/LiNbO$_3$ integration as a viable building block for self-referenced ultrafast pulse sources in low-loss Si$_3$N$_4$ photonics.

physics.optics↗

arXiv2025

Breaking the bandwidth-efficiency trade-off in soliton microcombs via mode coupling

Dissipative Kerr solitons in optical microresonators have emerged as a powerful tool for compact and coherent frequency comb generation. Advances in nanofabrication have allowed precise dispersion engineering, unlocking octave-spanning soliton combs that are essential for applications such as optical atomic clocks, frequency synthesis, precision spectroscopy, and astronomical spectrometer calibration. However, a key challenge hindering their practical deployment is the intrinsic bandwidth-efficiency trade-off: achieving broadband soliton generation requires large pump detuning, which suppresses power coupling and limits pump-to-comb conversion efficiencies to only a few percent. Recent efforts using pulsed pumping or coupled-resonator architectures have improved efficiency to several tens of percent, yet their bandwidths remain below one-tenth of an octave, inadequate for applications demanding wide spectral coverage. Here, we overcome this limitation by harnessing mode interactions between spatial modes within a single microresonator. The mode hybridization creates an additional power-transfer channel that supports large pump detuning while maintaining strong pump-to-resonator coupling, enabling broadband soliton formation at substantially reduced pump power. Using this approach, we demonstrate an octave-spanning soliton microcomb with a record pump-to-comb conversion efficiency exceeding 50%. These results resolve the fundamental bandwidth-efficiency dilemma in soliton microcombs and paves the way toward fully-integrated, high-efficiency, ultrabroad comb sources for next-generation photonic systems.

physics.optics↗

arXiv2025

High-performance Hybrid Lithium Niobate Electro-optic Modulators Integrated with Low-loss Silicon Nitride Waveguides on a Wafer-scale Silicon Photonics Platform

Heterogeneously-integrated electro-optic modulators (EOM) are demonstrated using the hybrid-mode concept, incorporating thin-film lithium niobate (LN) by bonding with silicon nitride (SiN) passive photonics. At wavelengths near 1550 nm, these EOMs demonstrated greater than 30 dB extinction ratio, 3.8 dB on-chip insertion loss, a low-frequency half-wave voltage-length product ($V_πL$) of 3.8 $V.{}cm$, and a 3-dB EO modulation bandwidth exceeding 110 GHz. This work demonstrates the combination of multi-layer low-loss SiN waveguides with high-performance LN EOMs made in a scalable fabrication process using conventional low-resistivity silicon (Si) wafers.

physics.optics↗

arXiv2024

Integrated resonant electro-optic comb enabled by platform-agnostic laser integration

The field of integrated photonics has significantly impacted numerous fields including communication, sensing, and quantum physics owing to the efficiency, speed, and compactness of its devices. However, the reliance on off-chip bulk lasers compromises the compact nature of these systems. While silicon photonics and III-V platforms have established integrated laser technologies, emerging demands for ultra-low optical loss, wider bandgaps, and optical nonlinearities necessitate other platforms. Developing integrated lasers on less mature platforms is arduous and costly due to limited throughput or unconventional process requirements. In response, we propose a novel platform-agnostic laser integration technique utilizing a singular design and process flow, applicable without modification to a diverse range of platforms. Leveraging a two-step micro-transfer printing method, we achieve nearly identical laser performance across platforms with refractive indices between 1.7 and 2.5. Experimental validation demonstrates strikingly similar laser characteristics between devices processed on lithium niobate and silicon nitride platforms. Furthermore, we showcase the integration of a laser with a resonant electro-optic comb generator on the thin-film lithium niobate platform, producing over 80 comb lines spanning 12 nm. This versatile technique transcends platform-specific limitations, facilitating applications like microwave photonics, handheld spectrometers, and cost-effective Lidar systems, across multiple platforms.

physics.optics↗

arXiv2021

Hybrid integrated mode-locked laser diodes with a silicon nitride extended cavity

Integrated semiconductor mode-locked lasers have shown promise in many applications and are readily fabricated using generic InP photonic integration platforms. However, the passive waveguides offered in such platforms have relatively high linear and nonlinear losses that limit the performance of these lasers. By extending such lasers with, for example, an external cavity the performance can be increased considerably. In this paper, we demonstrate for the first time that a high-performance mode-locked laser can be achieved with a butt-coupling integration technique using chip scale silicon nitride waveguides. A platform-independent SiN/SU8 coupler design is used to couple between the silicon nitride external cavity and the III/V active chip. Mode-locked lasers at 2.18 GHz and 15.5 GHz repetition rates are demonstrated with Lorentzian RF linewidths several orders of magnitude smaller than what has been demonstrated on monolithic InP platforms. The RF linewidth was 31 Hz for the 2.18 GHz laser.

physics.optics↗