This paper presents the design, optimization, fabrication, and characterization of a dual-output, wideband, thin-film lithium niobate Mach-Zehnder Modulator (TFLN-MZM). The device is designed with ridge etched waveguides for operation at a 1.55 $\mu$ m wavelength. The dual-output is achieved using a 2×2 multi-mode interference (MMI) splitter with an extinction ratio (ER) of over 40 dB. The measured DC half-wave voltage (V $_\pi$ ) is 1.02 V. To achieve wideband operation, segmented electrodes are optimized to provide both wideband index matching and low loss. Accordingly, the measured 3 dB bandwidth is 95 GHz and the radio-frequency (RF) electrode loss is 0.24 dB/(cm $\cdot$ GHz $^{1/2}$ ). The motivation for this device is in balanced microwave photonic links (MPLs) for Radio-Frequency-over-Fiber (RFoF) applications.

As the demand for data capacity in wireless networks and mobile communications continues to grow, they are moving toward higher carrier frequencies and wider modulation bandwidths. Unfortunately, electronic device performance degrades in association with increased frequency and modulation bandwidths, which inhibits the application of conventional microwave architectures, particularly in the millimeter wave and terahertz regimes. Alternatively, microwave photonic systems address these challenges by offering device and system performance with exceptionally higher operational bandwidths. The challenge, however, is the ability to monolithically integrate both electronic and photonic devices into functional components that provide ultra-wideband performance up into the millimeter wave and terahertz regions. In particular, such integration remains a major technical challenge due to the high dielectric permittivity of commonly used material platforms for photonic integrated circuits, such as silicon, indium phosphide, and lithium niobate. In this paper, we present a photonic receiver consisting of a broadband antenna and a low-drive-voltage modulator monolithically integrated on thin-film lithium niobate with a quartz handle. A free-space data link is demonstrated, achieving data rates up to 2.7 Gbps using quadrature amplitude modulation, with error vector magnitude as low as 3%. This work demonstrates the potential of thin-film lithium niobate for high-frequency, monolithically integrated radiofrequency and photonic devices to enable ultra-wideband millimeter wave-to-terahertz communication systems.

This work reports a sub-1 volt drive voltage (V_π) folded phase modulator utilizing capacitor-loaded traveling wave electrodes (CLTWEs). The implementation employs a low-loss CLTWE on a quartz (Qz) substrate, facilitating both broadband index matching and minimal RF loss. A series of phase modulators of varying lengths have been fabricated and subjected to experimental characterization. The measured loss for straight CLTWEs is 0.21 dB/(cm·GHz^1/2). The experimentally determined DC V_π is 0.52 V for a modulation length of 7.5 cm.

This letter presents low-loss monolithic Barium Titanium Oxide (BaTiO3), hereafter referred to as BTO, waveguides fabricated on a Silicon-on-insulator (SOI) platform, using a novel measurement approach based on optical back-scattering reflectometry (OBR). Utilizing this method, a low average propagation loss of 0.7 dB/cm was achieved for a straight waveguide which, to our knowledge, is the lowest propagation loss reported to date based on long BTO ridge-waveguides. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) highlight the smooth sidewalls responsible for lowering the waveguide loss. Design simulations and fabrication processes are presented, followed by optical characterization.

In this manuscript, we demonstrate the first phase modulator using titanium dioxide as a strip loaded waveguide on thin-film lithium niobate. The amorphous titanium dioxide was fabricated using RF reactive sputtering followed by a dielectric lift-off process. Two gold electrodes were deposited next to the waveguide by using the same process. This process eliminates the need for plasma etching or high-temperature vapor deposition methods, opening the door to fabrication on sensitive material systems. A propagation loss of 0.156 dB/mm and V π of 3.2 V at 1550 nm were experimentally measured and reported.