In-band full-duplex (IBFD) technology can double the spectrum utilization efficiency for wireless communications, and increase the data transmission rate of B5G and 6G networks and satellite communications. RF self-interference is the major challenge for the application of IBFD technology, which must be resolved. Compared with the conventional electronic method, the photonic self-interference cancellation (PSIC) technique has the advantages of wide bandwidth, high amplitude and time delay tuning precision, and immunity to electromagnetic interference. Integrating the PSIC system on chip can effectively reduce the size, weight, and power consumption and meet the application requirement, especially for mobile terminals and small satellite payloads. In this paper, the silicon integrated PSIC chip is presented first and demonstrated for IBFD communication. The integrated PSIC chip comprises function units including phase modulation, time delay and amplitude tuning, sideband filtering, and photodetection, which complete the matching conditions for RF self-interference cancellation. Over the wide frequency range of C, X, Ku, and K bands, from 5 GHz to 25 GHz, a cancellation depth of more than 20 dB is achieved with the narrowest bandwidth of 140 MHz. A maximum bandwidth of 630 MHz is obtained at a center frequency of 10 GHz. The full-duplex communication experiment at Ku-band by using the PSIC chip is carried out. Cancellation depths of 24.9 dB and 26.6 dB are measured for a bandwidth of 100 MHz at central frequencies of 12.4 GHz and 14.2 GHz, respectively, and the signal of interest (SOI) with 16-quadrature amplitude modulation is recovered successfully. The factors affecting the cancellation depth and maximum interference to the SOI ratio are investigated in detail. The performances of the integrated PSIC system including link gain, noise figure, receiving sensitivity, and spurious free dynamic range are characterized.

Electrically connected optical metasurfaces with high efficiencies are crucial for developing spatiotemporal metadevices with ultrahigh spatial and ultrafast temporal resolutions. While efficient metal–insulator–metal (MIM) metasurfaces containing discretized meta-atoms require additional electrodes, Babinet-inspired slot-antenna-based plasmonic metasurfaces suffer from low efficiencies and limited phase coverage for copolarized optical fields. Capitalizing on the concepts of conventional MIM and slot-antenna metasurfaces, we design and experimentally demonstrate a new type of optical reflective metasurfaces consisting of mirror-coupled slot antennas (MCSAs). By tuning the dimensions of rectangular-shaped nanoapertures atop a dielectric-coated gold mirror, we achieve efficient phase modulation within a sufficiently large range of 320 deg and realize functional phase-gradient metadevices for beam steering and beam splitting in the near-infrared range. The fabricated samples show (22 % ± 2 % ) diffraction efficiency for beam steering and (17 % ± 1 % ) for beam splitting at the wavelength of 790 nm. The considered MCSA configuration, dispensing with auxiliary electrodes, offers an alternative and promising platform for electrically controlled reflective spatiotemporal metasurfaces.

Noble metallic nanostructures with strong electric near-field enhancement can significantly improve nanoscale light–matter interactions and are critical for high-sensitivity surface-enhanced Raman spectroscopy (SERS). Here, we use an azimuthal vector beam (AVB) to illuminate the plasmonic tips circular cluster (PTCC) array to enhance the electric near-field intensity of the PTCC array, and then use it to improve SERS sensitivity. The PTCC array was prepared based on the self-assembled and inductive coupled plasmon (ICP) etching methods. The calculation results show that, compared with the linearly polarized beam (LPB) and radial vector beam excitations, the AVB excitation can obtain stronger electric near-field enhancement due to the strong resonant responses formed in the nanogap between adjacent plasmonic tips. Subsequently, our experimental results proved that AVB excitation increased SERS sensitivity to 10^-13 mol/L, which is two orders of magnitude higher than that of LPB excitation. Meanwhile, the PTCC array had excellent uniformity with the Raman enhancement factor calculated to be ∼2.4×108. This kind of vector light field enhancing Raman spectroscopy may be applied in the field of sensing technologies, such as the trace amount detection.

We present the generation of the nanosecond cylindrical vector beams (CVBs) in a two-mode fiber (TMF) and its applications of stimulated Raman scattering. The nanosecond (1064 nm, 10 ns, 10 Hz) CVBs have been directly produced with mode conversion efficiency of ～18 dB (98.4%) via an acoustically induced fiber grating, and then the stimulated Raman scattering signal is generated based on the transmission of the nanosecond CVBs in a 100-m-long TMF. The transverse mode intensity and polarization distributions of the first-order Stokes shift component (1116.8 nm) are consistent with the nanosecond CVBs pump pulse.

Surface-enhanced Raman spectroscopy (SERS) with high-sensitivity performance is a very necessary detection technology. Here, we present a method for increasing the performance of SERS based on silver triangular nanoprism arrays (ATNAs) vertically excited via a focused azimuthal vector beam (AVB). The ATNA substrates with different structural parameters are prepared based on the traditional self-assembled and modified film lift-off technique. Based on a theoretical model established adopting the structural parameters of the ATNA substrates, theoretical simulation results show that AVB excitation can achieve greater electric-field enhancement than linearly polarized beam (LPB) excitation. Experimental result indicates that SERS sensitivity obtained via AVB excitation is 10 13M (1 M = 1 mol/L) using rhodamine 6G (R6G) as the target analyte, which is 2 orders of magnitude lower than that of LPB excitation (10 11M). Meanwhile, the uniformity and reproducibility of the ATNA substrates are examined using Raman mapping and batch-to-batch measurement, respectively, and the Raman enhancement factor is calculated to be ～3.3×107. This method of vector light field excitation may be used to improve the SERS performance of the substrates in fields of ultra-sensitive Raman detection.