Excitation of higher-order modes in optofluidic photonic crystal fiber
Andrei Ruskuc,
Philipp Koehler,
Marius A. Weber,
Ana Andres-Arroyo,
Michael H. Frosz,
Philip St. J. Russell,
Tijmen G. Euser
Optics Express
26
(23)
30245-30254
(2018)
| Journal
| PDF
Higher-order modes up to LP33 are controllably excited in water-filled kagomé- and bandgap-style hollow-core photonic crystal fibers (HC-PCF). A spatial light modulator is used to create amplitude and phase distributions that closely match those of the fiber modes, resulting in typical launch efficiencies of 10–20% into the liquid-filled core. Modes, excited across the visible wavelength range, closely resemble those observed in air-filled kagomé HC-PCF and match numerical simulations. Mode indices are obtained by launching plane-waves at specific angles onto the fiber input-face and comparing the resulting intensity pattern to that of a particular mode. These results provide a framework for spatially-resolved sensing in HC-PCF microreactors and fiber-based optical manipulation.
Strong circular dichroism for the HE11 mode in twisted single-ring hollow-core photonic crystal fiber
Paul Roth,
Yang Chen,
Mehmet Can Günendi,
Ramin Beravat,
Nitin N. Edavalath,
Michael H. Frosz,
Goran Ahmed,
Gordon K. L. Wong,
Philip St. J. Russell
We report a series of experimental, analytical, and numerical studies demonstrating strong circular dichroism for the HE11-like core mode in helically twisted hollow-core single-ring photonic crystal fiber (SR-PCF), formed by spinning the preform during fiber drawing. In the SR-PCFs studied, the hollow core is surrounded by a single ring of nontouching capillaries. Coupling between these capillaries results in the formation of helical Bloch modes carrying orbital angular momentum. When twisted, strong circular birefringence appears in the ring, so that coupling to the core mode is possible for only one circular polarization state. The result is a SR-PCF that acts as a circular polarizer, offering 1.4 dB/m for the low-loss polarization state and 9.7 dB/m for the high-loss state over a 25 nm band centered at 1593 nm wavelength. In addition, we report for the first time that the vector fields of the helical Bloch modes are perfectly periodic when evaluated in cylindrical coordinates. Such fibers have many potential applications, such as generating circularly polarized light in gas-filled SR-PCF and realizing polarizing elements in the deep and vacuum ultraviolet.
Three-dimensional holographic optical manipulation through a high-numerical-aperture soft-glass multimode fibre
Ivo T. Leite,
Sergey Turtaev,
Xin Jiang,
Martin Siler,
Alfred Cuschieri,
Philip St. J. Russell,
Tomas Cizmar
Holographic optical tweezers (HOT) hold great promise for many applications in biophotonics, allowing the creation and measurement of minuscule forces on biomolecules, molecular motors and cells. Geometries used in HOT currently rely on bulk optics, and their exploitation in vivo is compromised by the optically turbid nature of tissues. We present an alternative HOT approach in which multiple three-dimensional (3D) traps are introduced through a high-numerical-aperture multimode optical fibre, thus enabling an equally versatile means of manipulation through channels having cross-section comparable to the size of a single cell. Our work demonstrates real-time manipulation of 3D arrangements of micro-objects, as well as manipulation inside otherwise inaccessible cavities. We show that the traps can be formed over fibre lengths exceeding 100 mm and positioned with nanometric resolution. The results provide the basis for holographic manipulation and other high-numerical-aperture techniques, including advanced microscopy, through single-core-fibre endoscopes deep inside living tissues and other complex environments.
Contact
TDSU Fibre Fabrication & Glass Studio Michael Frosz
Max Planck Institute for the Science of Light Staudtstr. 2 91058 Erlangen, Germany
