ABSTRACT
Optical vortex beams that carry orbital angular momentum (OAM), also known as OAM modes, have attracted considerable interest in recent years as they can comprise an additional degree of freedom for a variety of advanced classical and quantum optical applications. While canonical methods of OAM mode generation are effective, a method that can simultaneously generate and multiplex OAM modes with low loss and over broad spectral range is still in great demand. Here, via novel design of an optical fiber device referred to as a photonic lantern, where the radial mode index ("m") is neglected, for the first time we demonstrate the simultaneous generation and multiplexing of OAM modes with low loss and over the broadest spectral range to date (550 nm). We further confirm the potential of this approach to preserve the quality of studied OAM modes by fusion splicing the end-facet of the fabricated device to a delivery ring-core fiber (RCF).
ABSTRACT
We present a randomly disordered silica-air optical fiber featuring a 28.5% air filling fraction in the structured region, and low attenuation below 1 dB per meter at visible wavelengths. The quality of images transported through this fiber is shown to be comparable to, or even better than, that of images sent through commercial multicore imaging fiber. We demonstrate robust high-quality optical image transfer through 90 cm-long fibers with disordered silica-air structure, more than an order of magnitude improvement compared to previous disordered fiber imaging distances. The effects of variations of wavelength and feature size on transported image quality are investigated experimentally.
ABSTRACT
The fibre-optic microwave photonic link has become one of the basic building blocks for microwave photonics. Increasing the optical power at the receiver is the best way to improve all link performance metrics including gain, noise figure and dynamic range. Even though lasers can produce and photodetectors can receive optical powers on the order of a Watt or more, the power-handling capability of optical fibres is orders-of-magnitude lower. In this paper, we propose and demonstrate the use of few-mode fibres to bridge this power-handling gap, exploiting their unique features of small acousto-optic effective area, large effective areas of optical modes, as well as orthogonality and walk-off among spatial modes. Using specially designed few-mode fibres, we demonstrate order-of-magnitude improvements in link performances for single-channel and multiplexed transmission. This work represents the first step in few-mode microwave photonics. The spatial degrees of freedom can also offer other functionalities such as large, tunable delays based on modal dispersion and wavelength-independent lossless signal combining, which are indispensable in microwave photonics.
