Achieving beyond-100-GHz large-signal modulation bandwidth in hybrid silicon photonics Mach Zehnder modulators using thin film lithium niobate

Abstract

Mach-Zehnder electro-optic modulators (EOM) based on thin-film lithium niobate bonded to a silicon photonic waveguide circuit have been shown to achieve very high modulation bandwidths. Open eye-diagram measurements made in the time domain of beyond-small-signal modulation are used to support the modulation-sideband measurements in showing that such EOM’s can support high-frequency modulations well beyond 100 GHz.

Rejuvenating a Versatile Photonic Material: Thin‐Film Lithium Niobate

“…One of the main advantages of this method is the ease of processing. Several materials have been pursued in this regard, such as tantalum pentoxide (Ta 2 O 5 ), [29] chalcogenide glass (ChG), [70] silicon nitride (SiN, Si 3 N 4 ), [41,71,72,81,85,100,101,124] and titanium dioxide (TiO 2 ), [40] with reported propagation loss values as low as ∼1 dB cm −1 for plasma-enhanced chemical-vapor deposition Figure 3a), [71] dry-etched ( Figure 3b), [75,78] and SOI-bonded ( Figure 3d) [76,77,80,84] methods, while for nonlinear devices, rib-loaded [100,101] and dry-etched [102,105] have been the most commonly employed platforms. In comparison to platforms (a)-(c), platform (d) requires additional bonding and TFLN substrate removal steps.…”

“…[38,125] Figure 3d depicts such a structure. Common types of bonding are direct-bonding using SiO 2 , [76,77,80] or by using an adhesive polymer like BCB. [37,38,[67][68][69] However, directbonding is usually preferred due to stability and reliability issues with BCB, as previously pointed out in Section 2.1.…”

“…As a result of this Si waveguide narrowing, a disadvantage is the more interaction of optical mode with Si waveguide sidewalls . Fabrication steps for bonded-SOI TFLN platform [76,77,80,125] : a) Patterned SOI structure; b) TFLN (see Figure 2d) bonding onto the SOI wafer using SiO 2 or BCB; c) TFLN substrate removal; d) Prepared structure and associated optical mode simulation. At this step, metallic electrodes can be deposited on top in order to form LN photonic devices such as EOM and PPLN waveguides.…”

“…The same group has recently showed 20 Gbit s −1 data modulation with eye-diagrams and signal-to-noise ratio measurements up to 102 GHz. [77] In another TFLN EOM demonstration in 2018, Mercante et al [78] demonstrated a direct-etched TFLN phase modulator on quartz substrate. The devices exhibited ∼7-dB cm −1 propagation loss, and were characterized up to 500 GHz by optically-assisted methods.…”

“…In recent years, based on this rapidly-growing technology, a plethora of ultracompact integrated photonic devices and circuits, such as microdisk [59][60][61][62] and microring [46,[63][64][65][66] resonators, EO modulators, [67][68][69][70][71][72][73][74][75][76][77][78][79][80][81][82][83][84][85] acousto-optic modulators, [86][87][88][89] photodetector, [90] integrated single-photon detector, [91] grating couplers, [92][93][94][95][96] fiber-to-chip edge couplers, [97][98][99] wavelength Figure 2. Summary of the steps for fabrication of TFLN on Si wafers.…”