We propose and demonstrate an integrated microwave photonic sideband selector based on the thin-film lithium niobate (TFLN) platform by integrating an electro-optic Mach–Zehnder modulator (MZM) and a thermo-optic tunable flat-top microring filter. The sideband selector has two functions: electro-optic modulation of wideband RF signal and sideband selection. The microwave photonic sideband selector supports processing RF signals up to 40 GHz, with undesired sidebands effectively suppressed by more than 25 dB. The demonstrated device shows great potential for TFLN integrated technology in microwave photonic applications, such as mixing and frequency measurement.

Large-bandwidth, high-sensitivity, and large dynamic range electric field sensors are gradually replacing their traditional counterparts. The lithium-niobate-on-insulator (LNOI) material has emerged as an ideal platform for developing such devices, owing to its low optical loss, high electro-optical modulation efficiency, and significant bandwidth potential. In this paper, we propose and demonstrate an electric field sensor based on LNOI. The sensor consists of an asymmetric Mach–Zehnder interferometer (MZI) and a tapered dipole antenna array. The measured fiber-to-fiber loss is less than -6.7 dB, while the MZI structure exhibits an extinction ratio of greater than 20 dB. Moreover, 64-QAM signals at 2 GHz were measured, showing an error vector magnitude (EVM) of less than 8%.

Multispectral and polarized focusing and imaging are key functions that are vitally important for a broad range of optical applications. Conventional techniques generally require multiple shots to unveil desired optical information and are implemented via bulky multi-pass systems or mechanically moving parts that are difficult to integrate into compact and integrated optical systems. Here, a design of ultra-compact transversely dispersive metalens capable of both spectrum and polarization ellipticity recognition and reconstruction in just a single shot is demonstrated with both coherent and incoherent light. Our design is well suited for integrated and high-speed optical information analysis and can significantly reduce the size and weight of conventional devices while simplifying the process of collecting optical information, thereby promising for various applications, including machine vision, minimized spectrometers, material characterization, remote sensing, and other areas which require comprehensive optical analysis.

Lithium niobate on insulator (LNOI) is rising as one of the most promising platforms for integrated photonics due to the high-index-contrast and excellent material properties of lithium niobate, such as wideband transparency from visible to mid-infrared, large electro-optic, piezoelectric, and second-order harmonic coefficients. The fast-developing micro- and nano-structuring techniques on LNOI have enabled various structure, devices, systems, and applications. In this contribution, we review the latest developments in this platform, including ultra-high speed electro-optic modulators, optical frequency combs, opto-electro-mechanical system on chip, second-harmonic generation in periodically poled LN waveguides, and efficient edge coupling for LNOI.

The real-time measurement of the polarization and phase information of light is very important and desirable in optics. Metasurfaces can be used to achieve flexible wavefront control and can therefore be used to replace traditional optical elements to produce a highly integrated and extremely compact optical system. Here, we propose an efficient and compact optical multiparameter detection system based on a Hartmann–Shack array with 2×2 subarray metalenses. This system not only enables the efficient and accurate measurement of the spatial polarization profiles of optical beams via the inspection of foci amplitudes, but also measures the phase and phase-gradient profiles by analyzing foci displacements. In this work, details of the design of the elliptical silicon pillars for the metalens are described, and we achieve a high average focusing efficiency of 48% and a high spatial resolution. The performance of the system is validated by the experimental measurement of 22 scalar polarized beams, an azimuthally polarized beam, a radially polarized beam, and a vortex beam. The experimental results are in good agreement with theoretical predictions.

We have developed a cost-effective and highly compact 100-Gb/s coarse wavelength division multiplexing (CWDM) transmitter optical subassembly (TOSA) using lens-free hybrid integration. To achieve large alignment tolerances, distributed feedback laser diodes (DFB-LDs) are butt-coupled to a four-channel silica-based planar lightwave circuit (PLC) arrayed waveguide grating, with the silicon sub-mounts and PLC adhesively bonded. Then, a flexible printed circuit is employed to connect the internal DFB-LDs and the exterior of the TOSA package for radiofrequency signal transmission, eliminating the expensive ceramic feed-through. The packaged CWDM TOSA, which is 15.8mm×7.0mm×6.0mm in size, shows a side-mode suppression ratio of >40dB, a 3 dB bandwidth of >18GHz, and error-free transmission with an average optical output power of >0dBm and dynamic extinction ratio of >4.0dB at 25.78125 Gb/s over a 10 km single-mode fiber for all four lanes.

We have designed and realized an athermal 4-channel wavelength (de-)multiplexer in silicon nitride (SiN). Minimized thermal sensitivity is achieved in a wide wavelength range by using wide and narrow waveguides with low and different thermal-optic coefficients in the two arms of Mach–Zehnder interferometers (MZIs). The SiN core layer and SiO2 cladding layers are deposited by a low-temperature plasma-enhanced chemical vapor deposition process. The fabricated MZI filter exhibits a thermal sensitivity within ±2.0 pm/°C in a wavelength range of 55 nm to near 1300 nm. Then, an athermal (de-)multiplexer based on cascaded MZIs has been demonstrated with a crosstalk ≤ 22 dB and a thermal sensitivity <4.8 pm/°C for all four channels, reduced by 77% compared to a conventional SiN (de-)multiplexer. Owing to the passive operation and compatibility with the CMOS backend process, our devices have potential applications in 3D integration of photonics and electronics.