With the rapid development of integrated optics, bulky and curved traditional lenses cannot meet the requirements of on-chip optical systems. Alternatively, the metalenses based on the artificial subwavelength structure possess ultra-thin and lightweight characteristics, providing a potential candidate for on-chip optical systems. Nonetheless, most metalenses have a limited field-of-view (FOV) due to the prevalence of severe off-axis aberrations. In this work, we propose and design an on-chip metalens with wide FOV based on the quadratic phase. The metalens modulates the phase of the incident light with different lengths of gold nano-bands placed on the silicon-on-insulator substrate; thus, the quadratic distribution of the phase of the output light can be achieved by shifting the lengths of gold nano-bands and the output light is focused. The metalens can be focused on a large angle (∼120°, ranging from −60° to +60°). Furthermore, the metallic strips in the metalens are very thin with a thickness of 50 nm, which can be easily integrated into a chip. The monolithic metalens of broad FOV and ultrathin thickness will have great potential for applications in areas of sensing, imaging, and on-chip information processing.
Efficient directional excitation of planar surface plasmon polaritons (SPPs) has important and wide applications in micro-nano photonic technology. Recently, by using geometric phase and spin-orbit interaction, catenary structures have been...
With the rapid development of on-chip optics, integrated optical devices with better performance are desirable. Waveguide couplers are the typical integrated optical devices, allowing for the fast transmission and conversion of optical signals in a broad working band. However, traditional waveguide couplers are limited by the narrow operation band to couple the spatial light into the chip and the fixed unidirectional transmission of light flow. Furthermore, most of the couplers only realize unidirectional transmission under the illumination of the linear polarized light. In this work, a broadband polarization directional coupler based on a metallic catenary antenna integrated on a silicon-on-insulator (SOI) waveguide has been designed and demonstrated under the illumination of the circularly polarized light. By applying the genetic algorithm to optimize the multiple widths of the metallic catenary antenna, the numerical simulation results show that the extinction ratio of the coupler can be maintained larger than 18 dB in a wide operation band of 300 nm (from 1400 to 1700 nm). Moreover, the coupler can couple the spatial beam into the plane and transmit in the opposite direction by modulating the rotation direction of the incident light. The broadband polarization directional coupler might have great potential in integrated optoelectronic devices and on-chip optical devices.
Vortex lights with optical orbital angular momentum (OAM) have shown great promise in the areas of optical communication, optical manipulation and quantum optics. However, traditional methods for detecting the topological charge of vortex beams, such as interference and diffraction, are still challenging in miniaturization of the detection system and perfect matching of wave vectors. Here, a detection approach is proposed for measuring the topological charge of Laguerre-Gaussian (LG) vortex beam based on a catenary grating metasurface. According to the wave vector matching principle, the LG vortex beam can be coupled into surface plasmon polaritons (SPPs) waves propagating in different directions by using the well-designed catenary grating structure. The positive and negative of the topological charge can be distinguished by different arrangement of the catenary gratings. Besides, the propagation angle of the launched SPPs waves increases with the value of the topological charge. We believe that the proposed device would have a broader application prospect in high compact photonic integrated circuits.
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