The design of a dynamically tunable, dual-axicon beam expander for coupling into higher order modes in standard, large core step-index fiber is presented. A single mode of the optical fiber is excited, allowing bend-resistant propagation and efficient perseveration of brightness for a variety of applications. The coupling from the dual-axicon system is shown to be equivalent to utilizing the standard single axicon coupling system, with improved ease of use. The described optical train utilizes all high-purity fused silica optical components to allow very high peak and average powers for fiber coupling.
The phrase "fiber laser" is a ubiquitous but insufficiently detailed description, as powers can range from microwatts to kilowatts. Fiber core diameters can vary from 3-micron core diameter ultra-high NA fibers for supercontinuum generation to 85 micron or greater PCF fibers to generate high pulse energies. With appropriate nonlinear optics, fiber lasers can reach wavelengths ranges from the UV to the LWIR and pulse widths can range from ultrafast femtosecond lasers to continuous output. The appropriate selection of laser can minimize cost, maximize efficiency, and ease assembly challenges in biomedical systems. The advantages and design limitations of single-mode, LMA, and PCF fiber lasers, as necessary to understand the available system impact of fiber laser source selection and including methods to reach directly inaccessible wavelength ranges, maximize net efficiency, or shape the light inside of a fiber are discussed.
Recent experiments have generated great interest in combined wavlength (WDM) and spatial
(SDM) divison multiplexing using optical angular momentum (OAM) at data rates orders of magnitude
better than current telecommunication standards. We discuss here a class of novel fiber optic
devices that induce mode coupling along the optical axis of the fiber by sinusoidally varying the
refractive index. Using the analogy between the wave equation for weakly guiding fibers and the
paraxial equation, we review fibers that support Laguerre-Gauss modes and, motivated by these
works, demonstrate that similar fibers with different core shapes support Hermite-Gauss modes in
the same regime. Finally, we utilize these relations to demonstrate how one might generate different
orbital angular momentum states using induced coupling between Hermite-Gauss modes,
motivated by the works of many previous authors. We further describe a class of devices that
could generate either a mode with a defined orbital angular momentum, and support its propagation
along a fiber, or create a superposition of modes from a single modal input. Previous efforts
focused on the generation of OAM states in a fiber have required extremely exotic refractive index
profiles, and we present here a method based on already developed refrative index profiles and
manipulation techniques, specifically using fiber bragg gratings to drive modal coupling in a fiber,
in an effort to generate states with well defined OAM.
Conference Committee Involvement (2)
Novel Optical Systems Design and Optimization XIX
29 August 2016 | San Diego, California, United States
Novel Optical Systems Design and Optimization XVIII
12 August 2015 | San Diego, California, United States
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