Hollow fibers with a silver reflective coating enable convenient delivery of high energy pulsed lasers. Coupling efficiency can be near 100% and pulse dispersion is negligible. Such fibers have been used in CARS experiments, delivering 50 mJ / 5 ns pulse laser beams with wavelengths at 532 nm and 607 nm over a 5 m length.
Fiber Internal Diameter (ID)
Overall transmission in hollow fibers depends strongly on the fiber internal diameter (ID). We offer four different standard ID size options ranging from ID = 500 µm to 1500 µm, and all of these fibers are multimode. Bending of the fiber will affect the beam quality and lead to higher loss. For best results, an input beam should be focused straight into the hollow fiber with a relatively long focal length optic such that the focused spot size is about ½ the fiber ID.
Silver Reflective Layer
For the visible to NIR wavelength range (λ = 400 – 1100 nm), a bare silver layer is deposited on the inside of glass capillary tubing. The surface quality of the silver layer is vitally important, and OKSI has developed coating techniques to minimize surface roughness enabling relatively high transmission.
Coupling into silver-only hollow fibers is similar to coupling into our Mid-IR fibers, see here for more details. In general, a relatively long focal length lens should be used with the beam focused straight into the fiber.
A. Alexander, P. Hsu, J. A. Wehrmeyer, S. Roy, J. R. Gord, and J. M. Kriesel ” Gas-Phase Temperature Measurements at the Exhaust of a J85 Engine using Coherent Anti-Stokes Raman Scattering “, 53rd AIAA Aerospace Sciences Meeting. January 2015
Kriesel, Jason M., Gat, Nahum, and Plemmons, David, “Fiber Optics for Remote Delivery of High Power Pulsed Laser Beams,” Proceedings of the 48th AIAA Aerospace Sciences Meeting, Orlando, FL, January 2010.
Aluminum hollow core fibers
Hollow glass waveguides coated with a reflective aluminum layer provide an excellent fiber optic delivery solution for ultra-violet (UV) lasers spanning the wavelength range from 100 – 400 nm. For vacuum UV wavelengths the fibers can be purged with an inert gas.
Coupling into aluminum coated hollow fibers is similar to coupling into our Mid-IR fibers, see here for more details. In general, a relatively long focal length lens should be used with the beam focused straight into the fiber.
Additional information on aluminum coated hollow fibers can be found in the following article:
Yuji Matsuura and Mitsunobu Miyagi, “Hollow Optical Fibers for Ultraviolet and Vacuum Ultraviolet Light”, IEEE J. Selected Topics in Quantum Electronics, VOL. 10, NO. 6, (2004).
Fibers can be packaged with standard SMA 905, FC/PC type connectors, or left bare. The FC connectors have a 2 mm key. With the “bare” fiber option, there is no connector on the end of the fiber.
Fibers can be packaged with or without a protective jacket. We use standard furcation tubing, the fiber sits in an inner tube, surrounded by aramid fibers, with a PVC jacket on the outside. The jacket comes in a choice of different colors. For fibers with an ID < 750 µm, the jacket diameter is 3.0 mm, and for fibers with ID ≥ 750 µm, the jacket diameter is 3.8 mm.
OptoKnowledge assembles custom bundles that enable delivery of multiple laser sources in a single connector. Note: the fibers are side-by-side rather than fused. In addition to hollow fibers for the Mid-IR, we can also include standard solid core fibers for visible, NIR, and SWIR wavelengths.