Tapered fiber
A tapered fiber is a glass fiber with an extremely small diameter . To make them, you take a normal glass fiber and heat it locally, for example with a burner or with a carbon dioxide laser . The fiber is pulled apart at its ends so that it becomes thinner and longer. If the original fiber still has a diameter of typically 125 μm, the diameter of the drawn fiber is only in the range of 0.5 to 5 μm. Typical drawn fibers pass through a transition area into normal fibers due to the manufacturing process. This enables the simple coupling of laser light into such fibers.
With a drawn fiber, it is important to distinguish between the individual areas of the fiber. A normal fiber consists of a core with a high refractive index , which is surrounded by a cladding with a lower refractive index. The core with a diameter of typically 8 μm guides the light inside as an optical waveguide . In the drawn fiber, however, the diameter is much smaller than the wavelength of the light. That is why the light is not directed in the core but in the cladding.
Such fibers have recently become the subject of research, as they enable the generation of white light ( supercontinuum ). If you couple a light pulse of short duration, for example from a femtosecond laser , into such a fiber, you will find high power on a small area. The resulting high intensities can stimulate non-linear processes that lead to a broadening of the spectrum . This white light can be used for frequency comb generators , optical coherence tomography , lidar and multiphoton microscopy .
literature
- Paulo Ribeiro, Maria Raposo (Eds.): Photoptics 2015. Revised Selected Papers. Springer International Publishing, New York 2016, ISBN 978-3-319-30137-2 .
- Rainer Tutsch, Young-June Cho, Wei-Chih Wang, Hyungsuck Cho (eds.): Progress in Optomechatronic Technologies . Springer International Publishing, New York 2014, ISBN 978-3-319-05710-1 .
- Luc Thevenaz: Advanced Fiber Optics . Taylor & Francis Group, Lousanne 2011, ISBN 978-1-4398-3517-3 .
- Rolf Haug (Ed.): Advances in Solid State Physics . Volume 48, Springer Verlag, Berlin / Heidelberg 2009, ISBN 978-3-540-85858-4 .