Design of high-bandwidth, low-voltage and low-loss hybrid lithium niobate electro-optic modulators

Abstract

The past decade has seen significant growth in the field of thin film lithium niobate electro-optic modulators, which promise reduced voltage requirements and higher modulation bandwidths on a potentially integrated platform. This article discusses the state-of-the-art in thin film modulator technology and presents a simplified simulation technique for quickly optimizing a hybrid silicon- or silicon nitride-lithium niobate modulator. Also discussed are the feasibility of creating a 1 V half-wave voltage, 100 GHz bandwidth modulator, and the design specifications for a single hybrid silicon-lithium niobate platform optimized to operate across all telecommunication bands (between 1260 and 1675 nm wavelengths).

A modular fabrication process for thin-film lithium niobate modulators with silicon photonics

“…This is a factor of 1.6 times lower (better) than our previously reported hybrid bonded LN modulator [33] due to the reduced electrode gap (g) from 12 to 8 µm. The measured V π L is in good agreement with the calculated V π L = (n eff λg)/(2n 4 e r 33 Γ mo ), where λ, n e , r 33 , n eff and Γ mo are the optical wavelength, extra-ordinary refractive index of LN, EO coefficient of LN, the effective refractive index of the hybrid mode and the RF-to-optical mode overlap, respectively [34]. The EO coefficient (r 33 ) is 30.8 pm V −1 , while n eff and Γ mo values are extracted from eigenmode simulations (using Lumerical MODE Solutions).…”

“…Bonding of thin-film LN to patterned Si or silicon nitride (Si 3 N 4 ) waveguides offers a site-specific, modular, and scalable approach for realizing hybrid photonic circuits. Our integration process requires minimal processing of the EO material and provides additional optical functionality by integration with a mature Si photonics process [26,33,34]. A truly modular process that benefits small-volume end users would enable most of the critical steps that require the highest precision and sophistication to be performed at the foundry level, perhaps leveraging a multi-project wafer for cost reduction, and then the wafers can be diced into smaller sections and distributed to end users for final-stage customization (typically, electrode design and end facet polishing, etc).…”

Design Optimization of Silicon and Lithium Niobate Hybrid Integrated Traveling-Wave Mach-Zehnder Modulator

“…For this optimized structure, the width of the LN ridge waveguide is > 4 µm, which is already in the multimode regime, and the V π L product is not necessarily the smallest in these cases. This is different from common practices [16]. The design discussed in this paper is rather conservative, as the metal induced loss was theoretically kept below 0.01 dB/cm.…”

“…The EO frequency response m(ω) of such a TW EO MZI modulator described above can be expressed as [16]:…”

“…Yet, other optical functional devices, e.g. splitters and routing waveguides, can be fabricated on other matured material platforms, such as SOI or silicon nitride [4], [5], [7], [8], [10], [16]. This type of hybrid integrated modulators has been demonstrated with even better performances, e.g., more stable operating point control, as compared to the ones on monolithic LNOI [17].…”