For many of the developing applications, characterization requires the availability of multiple wavelengths, the source often ideally fiber coupled.
The Ren Group – a research team at the School of Physics and Astronomy, Monash University – has developed a broadband achromatic metafiber and used a SuperK FIANIUM supercontinuum white light laser to characterize it.
Meta-optics 101
Meta-optics[1] makes use of an array of meta-atoms a.k.a. artificial antennas to manipulate optical responses such as the amplitude, phase, and polarization of incident em-radiation, including light. They additionally possess unique physical characteristics of being flat, ultrathin, lightweight, and compact.
Compact non-conventional metalenses or even metastructures can thus be designed to achieve a complex suite of task-specific optical functions that is simply not possible using classical approaches. These functions include – broadly – diffraction-limited focusing, high focusing efficiency, beam steering, polarization control, and dispersion engineering. The primary overarching application areas are imaging and sensing.
Metafibers for telecoms and imaging
Meta-optics can be fabricated onto or into a surface using nanoimprint lithography techniques[2]. 3D laser nanoprinting based on 2-photon polymerization allows minute optical structures to be engineered onto any optical facet, even the output of a fiber tip[3]. This enables the functionalization of, for example, single-mode fibers for different photonic applications.
Ren et al[4] demonstrate a 3D achromatic diffractive metalens on the end face of a single-mode telecommunications fiber. Through appropriate engineering of the minute structures comprising the meta-optic, achromatic, and polarization-insensitive focusing is achieved across the entire near-infrared telecommunication wavelength band ranging from 1250 to 1650 nm.
Characterization at multiple wavelengths
The authors characterize their design and illustrate the resulting achromatic behavior at up to 8 different (equally spaced) wavelength channels spanning the entire 1250 to 1650 nm communications spectrum.
To do this they use an NKT Photonics supercontinuum white light fiber laser, the SuperK FIANIUM.
By coupling it with a wavelength selector, the authors were able to freely select the desired wavelengths for characterization, each with approximately 10 to 20 nm linewidth.
Summary
The key take-away is the capability for sharp achromatic imaging across broadband illumination via fiber.
By modifying this achievement to other wavelengths, the authors envisage multiple applications in femtosecond laser-assisted treatments, fiber sensing, hyperspectral endoscopic imaging, and more.
A broadband white light fiber-coupled source serves as an ideal characterization tool for achromacity performance in such cases, providing predictable optical characteristics at all wavelengths to be tested, and in turn ensuring the validity of the results.
References
[1] Principles, Functions, and Applications of Optical Meta-Lens
[2] Nanoimprint lithography, Wikipedia
[3] Optical Fiber-Integrated Metasurfaces: An Emerging Platform for Multiple Optical Applications
[4] An achromatic metafiber for focusing and imaging across the entire telecommunication range
The SuperK advantages
Our SuperK supercontinuum white light lasers are ideal for the characterization of advanced optical components, metamaterials, plasmonics, etc.
They are as broad as a lamp and as bright as a laser. They deliver high-brightness diffraction-limited light across the entire 390-2400 nm region. You can turn it into an ultra-tunable laser by adding one of our filters.
They are maintenance-free and the monolithic fiber architecture ensures excellent reliability and a lifetime of thousands of hours.
