Wenqi Yu

A photonic instantaneous microwave frequency measurement scheme based on frequency-to-time mapping and channelization is proposed. An unknown signal is divided into four channels and mixed with a broadband linear frequency-modulated signal. The frequency information is converted to the time domain, and the frequency measurement range has been expanded due to channelization. A simulation system has been constructed to demonstrate the effectiveness of the proposed method. A proof-of-concept experimental result shows that the frequency measurement errors can be kept in 20 MHz with a 10 MHz resolution, and the frequency measurement range is 1 GHz to 39 GHz.

We proposed a compact and efficient polarization rotator (PR) based on an asymmetric hybrid plasmonics waveguide (HPW) on the lithium-niobate-on-insulator (LNOI) platform. We focus on the design of rotation angle and balance between the two hybrid modes. The presented device exhibits a polarization extinction ratio as high as 59.58 dB and an insertion loss of 1.44 dB with the rotation length of only 13.7 μm. The fabrication tolerances and a suitable process are also discussed to meet the state-of-art technology.

We proposed a design of a fundamental TM mode waveguide optical isolator using lithium niobate on insulator (LNOI) and deposited magneto-optical film. The optical isolator adopts an asymmetric Mach-Zehnder interferometer (MZI) structure composed of two 12 MMIs, non-reciprocal and reciprocal waveguides. We used three methods to calculate the non-reciprocal phase shift (NRPS) of the lithium niobate (LN)/ Ce: YIG composite waveguide and got similar results. The device shows about 51.98 nm 30 dB isolation bandwidth and 1.20 dB simulated insertion loss at the wavelength of 1550 nm. The fabrication tolerances and a suitable process are also discussed to meet the state-of-art technology and material properties.

A broadband and compact TE-pass/TM-stop polarizer is presented based on hybrid plasmonic grating (HPG) on an x-cut Lithium-Niobate-on-isolator (LNOI) platform. By comprehensively analyzing the effects of metal width on mode effective index, mode similarity, and mode conversion, we demonstrate the structure with a narrower metal width. The simulation results indicate that the polarizer with a compact length of 9 μm achieves an extinction ratio over 20 dB within the wavelength range from 1470 nm to 1700 nm. The insertion loss is below 2.3 dB in C-band. Furthermore, the polarizer exhibits large fabrication tolerance to current fabrication technology.

A novel non-planar coding metasurface optimized by discrete particle swarm algorithm (DPSO) is proposed in terms of the property of wideband radar cross-section (RCS) and diffuse scattering. The design consists of two unit cells, “0” and “1”, which have a 180° ± 37° phase difference for phase interference cancellation. The 10 dB monostatic RCS reduction frequency range of the metasurface is from 6.4 to 29.6 GHz, and its bandwidth ratio is 4.62:1, under normal incidence of the two polarizations. Compared to the planar surface, the non-planar surface has a greater bandwidth with respect to the monostatic and bistatic RCS reduction. The results declare its properties of ultra-wideband, angle insensitivity, and polarization insensitivity. Finally, the theoretical analysis, simulation, and experimental results match perfectly, indicating that the metasurface can be used in the RCS reduction or other microwave applications with wider RCS reduction and diffuse scattering.

An all-pass racetrack-resonator-Bragg gratings (APRR-BG) on thin-film lithium niobate on insulator (LNOI) based coupling resonant system is proposed to generate tunable electromagnetically induced transparency (EIT)-like transmission. The structure is a normal all-pass racetrack-resonator with two Bragg gratings inscribed within the straight waveguides, which introduces two different optical pathways in essence, inducing EIT-like spectrum as a result. We investigate the linewidth, and tunability of the EIT-like spectrum, and manufacturing tolerance of the resonant system by utilising the transfer matrix method. The simulation results indicate an extremely narrow linewidth of several picometers, and a high voltage sensitivity of $0.338\ GHz/V@1550\,nm$ , which indicates potential for optical filter, optical switching, and sensing of the system.

Radar warning receiver (RWR) plays a significant role in detecting weapon radar. The instantaneous frequency measurement (IFM) section with fast measuring response, large measurement bandwidth, moderate accuracy, and sensitivity is important for an all-threat-covered RWR. In this IFM method, a phase modulator (PM) in combination with a differentiation structure is employed to get rid of the DC drifting and makes the power response is a strict monotonous function of the input frequency. Therefore, the unambiguous determination can be made in a very large range, which guarantees the fast measuring response. According to the theoretical analysis, a strict monotonous amplitude comparison function (ACF) with the covering range higher than 40 GHz can be achieved. Besides, no filter or dispersion elements (DE) such as optical fibers are required, which makes the structure be very concise to meet the potential for integration in any receiving systems. Due to the limit operation range of the PM, only the range from 0.1 GHz to 25 GHz is demonstrated. The measurement error can be lower than 3%. Especially, benefited by the balance photo-diode (BPD), the sensitivity is good without any noise cancellation processing. The error of lower than 10% will be promised when the RF power level is - 40 dBm.