Haijin Huang

High efficiency and a compact footprint are desired properties for electro-optic modulators. In this paper, we propose, theoretically investigate, and experimentally demonstrate a recirculating phase modulator, which increases the modulation efficiency by modulating the optical field several times in a non-resonant waveguide structure. The “recycling” of light is achieved by looping the optical path that exits the phase modulator back and coupling it to a higher order waveguide mode, which then repeats its passage through the phase modulator. By looping the light back twice, we were able to demonstrate a recirculating phase modulator that requires nine times lower power to generate the same modulation index of a single pass phase modulator. This approach to modulation efficiency enhancement is promising for the design of advanced tunable electro-optical frequency comb generators and other electro-optical devices with defined operational frequency bandwidths.

Lithium niobate on insulator (LNOI) has been demonstrated as a promising platform for photonic integrated circuits (PICs), thanks to its excellent properties such as strong electro-optic effect, low material loss and wide transparency window. In this paper, we propose and demonstrate a monolithic PIC for high-speed data communication application on a lithium-niobate-etchless platform with silicon nitride (Si3N4) as a loading material. The fabricated PIC consists of four racetrack resonator modulators and a pair of four-channel mode (de)multiplexers, which shows high data modulation rate of 70 Gbps for single channel and the total data throughput reaches up to 280 Gbps. To the best of our knowledge, this is the first demonstration of PIC consisting of high-speed electro-optical modulators and (de)multiplexers with such high data capacity on Si3N4-LNOI hybrid platform, which opens up new avenues for achieving large-scale monolithic integration on LNOI platform in future.

Electro-optic (EO) modulators, which convert signals from the electrical to optical domain plays a key role in modern optical communication systems. Lithium niobate on insulator (LNOI) technology has emerged as a competitive solution to realize high-performance integrated EO modulators. In this Letter, we design and experimentally demonstrate a Mach–Zehnder interferometer-based modulator on a silicon nitride loaded LNOI platform, which not only takes full advantage of the excellent EO effect of L i N b O 3 , but also avoids the direct etching of L i N b O 3 thin film. The measured half-wave voltage length product of the fabricated modulator is 2.24 V·cm, and the extinction ratio is ∼ 20 d B . Moreover, the 3 dB EO bandwidth is ∼ 30 G H z , while the modulated data rate for on–off key signals can reach up to 80 Gbps.