Abstract
Nanophotonic waveguides are the building blocks of integrated photonics. To date, while quarter-wave plates (QWPs) are widely used as common components for a wide range of applications in free space, there are almost no reports of Integratable QWPs being able to manipulate the angular momentum (AM) of photons inside nanophotonic waveguides. Here, we demonstrate two kinds of Integratable QWPs respectively based on the concept of abrupt phase change and birefringence effect. The orientation of the equivalent optical axis of an Integratable QWP is designable. Remarkably, a combination of two integratable QWPs with different equivalent optical axes leads to an integrated system that performances one-way AM conversion. Moreover, this system can be used as a point source that can excite different patterns on a metal surface via directional excitation of surface plasmon polaritons (SPP). These results allow for the control of AM of light in nanophotonic waveguides, which are crucial for various applications with limited physical space, such as on-chip bio-sensing and integrated quantum information processing.
Highlights
Via near-field excitation of surface plasmon polaritons (SPP) in thin metallic films
When light travels from port A to port B, a fundamental quasi-TM mode, whose predominant polarization component points along the x-axis, transforms into another quasi-linearly polarized mode with the dominant polarization component orienting along (φ = − π/4)-direction, where φ is the angle down from the positive x-axis
On the other hand, when light travels in the opposite direction (B to A), the same quasi-TM mode transforms into a novel quasi-circularly polarized mode with a longitudinal optical vortex component
Summary
Via near-field excitation of surface plasmon polaritons (SPP) in thin metallic films. On the other hand, when light travels in the opposite direction (B to A), the same quasi-TM mode transforms into a novel quasi-circularly polarized mode with a longitudinal optical vortex component.
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