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A novel compact left-handed delay line using four-cell of complementary split-ring resonators (CSRRs) has been designed, fabricated and characterised. It is found that the cell separation of CSRRs has significant effects on time delay. To obtain maximum time delay, each cell separation must be individually tuned and optimised. The results show that cell separation optimisation can prolong the delay time from 0.6 to 6.08 ns, increased by more than 90%. Furthermore, varactor diodes were embedded in the delay line to provide tunability. It is verified experimentally that the delay time can be tuned from 0.08 to 5.6 ns by varying DC bias from 0 to −20 V. In addition, a new equivalent circuit model has been developed and verified both numerically and experimentally, to take into account of the magnetic coupling between the rings in the adjacent cells, which has been neglected so far in published works. The proposed analysis reveals that such magnetic coupling can be sometimes very strong and has significant effects on circuit performance.

Integrated lithium niobate (LN) photonics is a promising platform for future chip-scale microwave photonics systems owing to its unique electro-optic properties, low optical loss and excellent scalability. A key enabler for such systems is a highly linear electro-optic modulator that could faithfully covert analog electrical signals into optical signals. In this work, we demonstrate a monolithic integrated LN modulator with an ultrahigh spurious-free dynamic range (SFDR) of 120.04 dB Hz4/5 at 1 GHz, using a ring-assisted Mach-Zehnder interferometer configuration. The excellent synergy between the intrinsically linear electro-optic response of LN and an optimized linearization strategy allows us to fully suppress the cubic terms of third-order intermodulation distortions (IMD3) without active feedback controls, leading to ~ 20 dB improvement over previous results in the thin-film LN platform. Our ultra-high-linearity LN modulators could become a core building block for future large-scale functional microwave photonic integrated circuits, by further integration with other high-performance components like low-loss delay lines, tunable filters and phase shifters available on the LN platform.