High-performance and compact integrated photonics platform based on silicon rich nitride-lithium niobate on insulator APL Photonics 6, 116102 (2021);

Growing global data traffic requires high-performance modulators with a compact size, a large bandwidth, a low optical loss, and a small power consumption. A careful trade-off among these parameters usually has to be made when designing such a device. Here, we propose and demonstrate an electro-optic ring modulator on the thin-film lithium niobate platform without compromising between any performances. The device exhibits a low on-chip loss of about 0.15 dB with a high intrinsic quality-factor (Q-factor) of 7.7 × 10 5 . Since a pure coupling modulation is employed, the photon lifetime is no longer a limiting factor for the modulation speed. A large electro-optic bandwidth is obtained without any roll-off up to 67 GHz. The device, with a footprint of 3.4 m m × 0.7 m m , also exhibits a low half-wave voltage of 1.75 V, corresponding to a half-wave voltage length product of 0.35 V ⋅ c m considering the 2-mm-long modulation section. Driverless data transmission up to 240 Gb/s is also demonstrated with a peak-to-peak driving voltage of 0.75 V.

Electro-optic (EO) modulators with a high modulation bandwidth are indispensable parts of an optical interconnect system. A key requirement for an energy-efficient EO modulator is the low drive voltage, which can be provided using a standard complementary metal oxide semiconductor circuity without an amplifying driver. Thin-film lithium niobate has emerged as a new promising platform, and shown its capable of achieving driverless and high-speed EO modulators. In this paper, we report a compact high-performance modulator based on the thin-film lithium niobate platform on a silicon substrate. The periodic capacitively loaded travelling-wave electrode is employed to achieve a large modulation bandwidth and a low drive voltage, which can support a driverless single-lane 100Gbaud operation. The folded modulation section design also helps to reduce the device length by almost two thirds. The fabricated device represents a large EO bandwidth of 45GHz with a half-wave voltage of 0.7V. The driverless transmission of a 100Gbaud 4-level pulse amplitude modulation signal is demonstrated with a power consumption of 4.49fj/bit and a bit-error rate below the KP4 forward-error correction threshold of 2.4×10−4.

Silicon nitride (SiN) emerges as an important platform for ultralow loss photonic integrations with complementary metal‐oxide‐semiconductor compatibility. However, active devices, such as modulators, are difficult to realize on pure SiN due to the lack of any electro‐optic (EO) properties of the material. Here, an SiN and lithium niobate (LN) heterogenous integration platform supporting high‐performance EO modulators on SiN waveguide circuits is introduced. An efficient evanescent coupling structure is realized for low‐loss light transitions between the SiN waveguide and the LN ridge waveguide with a measured mode transition loss of only 0.4 dB. Based on this heterogeneous platform, an EO Mach–Zender interference modulator on SiN is built with unprecedented loss, efficiency, and bandwidth performances. A half‐wave voltage of 4.3 V with a modulation bandwidth of 37 GHz and an overall insertion loss of 1 dB is measured for a 7‐mm long device. Data transmission up to 128 Gb s−1 with a bit‐error‐rate of <2.4 × 10‐4 is also demonstrated.

High-performance silicon and thin-film lithium niobate hybrid electro-optic modulators are demonstrated. In order to break the voltage–bandwidth limit in a normal traveling-wave modulator, a periodic capacitively loaded traveling-wave electrode is employed in this hybrid platform. The silicon substrate is undercut-etched to achieve index matching of the optical wave and microwave. A hybrid waveguide with a lithium niobate thin film bonded on a silicon wire is employed. Lithium niobate etching is not required for making the hybrid optical waveguides. We realize an intensity modulator of 12.5 mm long modulation section, which exhibits a low half-wave voltage of 1.7 V and a large 3 dB modulation bandwidth of >70 GHz. Data transmissions with various modulation formats beyond 100 Gbit/s are successfully achieved with dynamic extinction ratios of >8 dB. Combining the advantages of the silicon and thin-film lithium niobate platforms, a compact dual polarization coherent modulator is also experimentally demonstrated, on which 96 Gbaud 16-level quadrature amplitude modulation signals in both polarizations are successfully transmitted.