We propose a novel polarization-maintaining index-guiding photonic crystal fiber (PCF). It is composed of a solid silica core and a cladding with squeezed-hexagonal-lattice elliptical air holes. Using a full-vector finite-element method, we study the modal birefringence of the fundamental modes in such PCFs. Numerical result shows that very high modal birefringence with a magnitude of the order of ${10}^{-2}$ around $1550\mathrm{nm}$ has been obtained. Furthermore, large normal dispersion appears over a wide range of wavelengths in both orthogonal polarizations.

A radio frequency memory (RFM) based on microwave photonic mixing and digital RFM is proposed and demonstrated. By introducing the microwave photonic mixing, the operational frequency range is largely extended. Besides, the mixing spurs are effectively suppressed, which is important to guarantee the system efficiency and avoid generating significant feature for the jamming recognition. Meanwhile, by applying the digital RFM, flexible modulation and reconstruction are achieved. A proof-of-concept experiment is carried out. The wide working frequency range from C- to Ka- bands is achieved. The mixing spurs over the 0–40 GHz frequency range are experimentally suppressed. Radar imaging is successfully deceived. A radar waveform with a bandwidth of 500 MHz in the K band is successfully received and reconstructed. Two false targets are added. To the best of our knowledge, it is the first time that a photonics-assisted RFM is reported to have the functions of storage, flexible modulation, and reconstruction with wideband RF signals at a high frequency. The proposed scheme shows the great potential to be applied in electronic warfare, electronic environment simulation and testing, and so on.

Vertical slots are used to reduce the nonlinearity of silicon-on-insulator waveguides. In properly designed slot waveguides, approximately 50% of the optical power can be confined in the air-slot and air-cladding region. Compared with a strip waveguide, a factor greater than 15 times more reduction in the real part of nonlinear coefficient can be achieved in the 100-nm wavelength range. In addition, vertical-slot waveguides exhibit large negative chromatic dispersion, which will induce phase mismatch and further suppress nonlinear parametric effects.

We report greatly enhanced transmission distance of multimode vertical-cavity surface-emitting lasers (MM-VCSELs) over standard single-mode fiber using optical injection locking. Transmission distance as high as 90 km is achieved at 10 Gb/s by frequency chirp inversion and higher order transverse mode suppression.