High-power photonic crystal fibers

Abstract

Fiber lasers deliver excellent beam-quality and high efficiency in a robust and largely maintenance-free format, and are now able to do so with output powers in the kilowatt regime. Consequently, fiber lasers have become an attractive alternative to solid-state and gas lasers for e.g. material processing like welding, cutting and marking. The all-glass air-clad photonic crystal fibers (PCFs) combine large mode-field diameters (currently up to 40 µm), high numerical aperture (typically in the 0.6-0.65 range), high pump absorption (30 dB/m demonstrated in ytterbium) and excellent high-power handling (kW CW and mJ pulses demonstrated). These properties have made this fiber type one of the most promising candidates for the future high-power fiber laser and amplifier systems that are expected to replace many of the traditional systems in use today. To utilize the high numerical aperture and large mode-field diameters of the air-clad PCFs, special care must be taken in the system integration. In this paper, we will show examples of how these fibers can be integrated in laser and amplifier sub-assemblies with standard fiber pump-interfaces for use with single-emitter diodes or diode-bar pump sources. Moreover, we report on the most recent advances in fiber design including rod-type fibers and broadband polarizing ytterbium-doped large-mode-area air-clad fibers. Finally, we will review the latest results on PCF-based amplifier and laser configurations with special focus on high-power CW systems and high-energy pulsed configurations.

Theoretical Investigation of Bandwidth in Multimode Step-Index Silica Photonic Crystal Fibers

“…Nowadays, PCFs are important since they can be implemented for many applications, such as supercontinuum light generation [18][19][20], light wavelength conversion [21,22], optical fluids [23], and different sensing area [24]. The width of the PCF material between the holes of the cladding determines the NA of the PCF, which is normally limited to NA 0.5-0.6 [25][26][27]. Sometimes, PCFs considered include heavy metal oxide glass fibers [28] and liquid-filled hollow-core fibers for specific applications [29].…”

Calculation of Bandwidth of Multimode Step-Index Polymer Photonic Crystal Fibers

“…PCFs have been used in a variety of applications, including dispersion [ 14 , 15 , 16 ], supercontinuum production [ 17 , 18 , 19 ], birefringence [ 20 ], optofluidics [ 21 ], wavelength conversion [ 22 , 23 ] and sensing [ 24 , 25 ]. A typical numerical aperture of PCFs is NA = 0.5–0.6 [ 26 , 27 , 28 , 29 , 30 ]. With high NA PCFs, lensless beam focusing with the outstanding resolution has been recorded [ 31 ].…”

Piston phase error due to bending of delivery fiber

“…In other words, the delivery fiber length and the delivery power limit each other for propagating narrow linewidth laser beams. Photonic Crystal Fiber (PCF) 3 with its core diameter of 40 µm can maintain good beam quality (M 2 ≤1.3). Based on SBS threshold calculations, 2 such a PCF of 2-meter in length may deliver laser beam of 200W power without SBS, and, using delivery fibers is a viable option.…”