Thin‐film lithium niobate on insulator (LNOI) is a promising platform for optical communications, microwave photonics, and quantum technologies. While many high‐performance devices like electro‐optic modulators and frequency comb sources have been achieved on LNOI platform, it remains challenging to realize photodetectors (PDs) on LNOI platform using simple and low‐cost fabrication techniques. 2D materials are excellent candidates to achieve photodetection since they feature strong light‐matter interaction, excellent mechanical flexibility, and potential large‐scale complementary metal–oxide–semiconductor‐compatible fabrication. Herein, this demand is addressed using an LNOI‐2D material platform, and two types of high‐performance LNOI waveguide‐integrated 2D material PDs, namely graphene and tellurium (Te), are addressed. Specifically, the LNOI‐graphene PDs feature broadband operations at telecom and visible wavelengths, high normalized photocurrent‐to‐dark current ratios up to 3 × 10⁶ W⁻¹, and large 3‐dB photoelectric bandwidths of ≈40 GHz, simultaneously. The LNOI‐Te PDs on the other hand provide ultrahigh responsivities of 7 A W⁻¹ under 0.5 V bias for telecom signals while supporting GHz frequency responses. The results show that the versatile properties of 2D materials and their excellent compatibility with LNOI waveguides could provide important low‐cost solutions for system operating point monitoring and high‐speed photoelectric conversion in future LNOI photonic integrated circuits.

We report a photonic radio frequency (RF) self-interference cancellation (SIC) and harmonic down-conversion (HDC) scheme based on a dual-parallel dual-drive Mach-Zehnder modulator (DDMZM). The proposed scheme can eliminate the chromatic-dispersion induced power fading (CDIP) effect and thus is very suitable for in-band full-duplex (IBFD) radio-over-fiber (ROF) system. The self-interference RF signal is directly cancelled in optical domain, which overcomes the electronics bottleneck limitation of electrical SIC. Moreover, the HDC allows us to use a cost-effective low frequency local oscillation (LO) source to down-convert a high-frequency RF signal into an intermediate frequency (IF) band. In addition, the harmonic odd-order single-sideband (SSB) down-conversion is naturally free from the CDIP effect. The proposed photonic SIC+HDC system is theoretically analyzed and experimentally verified.

We report a polarization manipulated Fourier domain mode-locked optoelectronic oscillator (FDML-OEO) using a polarization modulator (PolM). Frequency and bandwidth doubling linearly chirped microwave waveforms (LCMWs) are generated from a PolM-based FDML-OEO. The multiplying operation is capable of increasing the frequency and bandwidth of LCMWs, which doubles the time-bandwidth product of the LCMWs and makes it possible to increase the center frequency of the LCMWs beyond the bandwidth of the optical modulator. Moreover, by simply adding the other laser diode, it is also possible to generate a dual-chirp LCMW. The polarization manipulated of two optical signals avoids the undesired beating signals from optical carriers. Thus, an electrical bandpass filter which is essential in previous work is no longer required. To the best of our knowledge, this is the first time that polarization manipulation is used in FDML-OEO, which can further satisfy the demands of modern radars in terms of improved range-Doppler resolution, higher carrier frequency, and larger bandwidth.

The terahertz (THz) range, bridging microwave and infrared frequencies, enables advanced imaging, sensing, communications, and spectroscopy. Analogous to microwave photonics, terahertz photonics offers a promising optical solution to critical THz challenges-THz-optical interfacing, including THz-optic modulation and optical generation of THz waves. We address these with a monolithic integrated photonic chip enabling efficient THz-optical bidirectional interaction. Leveraging strong second-order optical nonlinearity and optical/THz confinement in thin-film lithium niobate on quartz, the chip supports efficient THz-optic modulation and continuous THz generation up to 500 GHz. The measured continuous wave THz generation efficiency of 4.8 × 10⁻⁶/W at 500 GHz also marks a tenfold improvement over existing lithium niobate-based tunable THz generation devices. We further leverage the coherent nature of the optical THz generation process and on-chip modulators to realize 65 GHz high-speed electro-THz modulation. The chip-scale THz-photonic platform enables more compact, efficient, and cost-effective THz systems for communications, sensing, and spectroscopy.

We propose a photonic scheme to generate dual-chirp microwave waveforms based on a widely tunable optoelectronic oscillator (OEO) using a dual-polarization dual-drive Mach-Zehnder modulator (DP-DDMZM). The upper DDMZM is properly biased to serve as a phase modulator and further constructs OEO loop to generate radio frequency (RF). The lower DDMZM injected by the combination of the RF and a single-chirp signal is utilized to generate a dual-chirp microwave waveform with an arbitrarily tunable central frequency. The RF from the OEO replaces external millimeter-wave source in our scheme, which improves the phase noise performance of RF in high-frequency range, alleviates the complexity of the system, and increases the possibility of integration. Dual-chirp microwave waveforms centered at 10 GHz with a bandwidths of 0.4 GHz and 1 GHz, and centered at 15 GHz with a bandwidth of 0.4 GHz are successfully generated. The proposed scheme is theoretically analyzed and experimentally demonstrated.