Since the emergence of optical fiber communications, lithium niobate (LN) has been the material of choice for electro-optic modulators, featuring high data bandwidth and excellent signal fidelity. ...Conventional LN modulators however are bulky, expensive and power hungry, and cannot meet the growing demand in modern optical data links. Chip-scale, highly integrated, LN modulators could offer solutions to this problem, yet the fabrication of low-loss devices in LN thin films has been challenging. Here we overcome this hurdle and demonstrate monolithically integrated LN electro-optic modulators that are significantly smaller and more efficient than traditional bulk LN devices, while preserving LN's excellent material properties. Our compact LN electro-optic platform consists of low-loss nanoscale LN waveguides, micro-ring resonators and miniaturized Mach-Zehnder interferometers, fabricated by directly shaping LN thin films into sub-wavelength structures. The efficient confinement of both optical and microwave fields at the nanoscale dramatically improves the device performances featuring a half-wave electro-optic modulation efficiency of 1.8 V∙cm while operating at data rates up to 40 Gbps. Our monolithic LN nanophotonic platform enables dense integration of high-performance active components, opening new avenues for future high-speed, low power and cost-effective communication networks.
Microresonator Kerr frequency combs could provide miniaturised solutions for a wide range of applications. Many of these applications however require further manipulation of the generated frequency ...comb signal using photonic elements with strong second-order nonlinearity (χ
). To date these functionalities have largely been implemented as discrete components due to material limitations, which comes at the expense of extra system complexity and increased optical losses. Here we demonstrate the generation, filtering and electro-optic modulation of a frequency comb on a single monolithic integrated chip, using a nanophotonic lithium-niobate platform that simultaneously possesses large electro-optic (χ
) and Kerr (χ
) nonlinearities, and low optical losses. We generate broadband Kerr frequency combs using a dispersion-engineered high-Q lithium-niobate microresonator, select a single comb line using an electrically programmable add-drop filter, and modulate the intensity of the selected line. Our results pave the way towards monolithic integrated frequency comb solutions for spectroscopy, data communication, ranging and quantum photonics.
Thin-film lithium niobate (LN) photonic integrated circuits (PICs) could enable ultrahigh performance in electro-optic and nonlinear optical devices. To date, realizations have been limited to ...chip-scale proof-of-concepts. Here we demonstrate monolithic LN PICs fabricated on 4- and 6-inch wafers with deep ultraviolet lithography and show smooth and uniform etching, achieving 0.27 dB/cm optical propagation loss on wafer-scale. Our results show that LN PICs are fundamentally scalable and can be highly cost-effective.
Electro-optic modulators (EOMs) convert signals from the electrical to the optical domain. They are at the heart of optical communication, microwave signal processing, sensing, and quantum ...technologies. Next-generation EOMs require high-density integration, low cost, and high performance simultaneously, which are difficult to achieve with established integrated photonics platforms. Thin-film lithium niobate (LN) has recently emerged as a strong contender owing to its high intrinsic electro-optic (EO) efficiency, industry-proven performance, robustness, and, importantly, the rapid development of scalable fabrication techniques. The thin-film LN platform inherits nearly all the material advantages from the legacy bulk LN devices and amplifies them with a smaller footprint, wider bandwidths, and lower power consumption. Since the first adoption of commercial thin-film LN wafers only a few years ago, the overall performance of thin-film LN modulators is already comparable with, if not exceeding, the performance of the best alternatives based on mature platforms such as silicon and indium phosphide, which have benefited from many decades of research and development. In this mini-review, we explain the principles and technical advances that have enabled state-of-the-art LN modulator demonstrations. We discuss several approaches, their advantages and challenges. We also outline the paths to follow if LN modulators are to improve further, and we provide a perspective on what we believe their performance could become in the future. Finally, as the integrated LN modulator is a key subcomponent of more complex photonic functionalities, we look forward to exciting opportunities for larger-scale LN EO circuits beyond single components.
Electro-optic phase modulators are critical components in modern communication, microwave photonic, and quantum photonic systems. Important for these applications is to achieve modulators with low ...half-wave voltage at high frequencies. Here, we demonstrate an integrated phase modulator, based on a thin-film lithium niobite platform, which simultaneously features small on-chip loss (~1 dB) and low half-wave voltage over a large spectral range (3.5-4.5 V at 5-40 GHz). By driving the modulator with a strong 30-GHz microwave signal corresponding to around four half-wave voltages, we generate an optical frequency comb consisting of over 40 sidebands spanning 10 nm in the telecom L-band. The high-electro-optic performance combined with the high-RF power-handling ability (3.1 W) of our integrated phase modulator is crucial for future photonics and microwave systems.
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