Novel Dopant Tailored Fibers Using Vapor Phase Chelate Delivery Technique

Abstract

The vapor phase chelate delivery (VPCD) technique in conjunction with the modified chemical vapor deposition (MCVD) process is adopted to fabricate fibers with customized doping profiles. The three large‐mode area (LMA) step‐index fibers with different rare‐earth doping profiles in the core region, such as uniform doping, centralized doping, and circumferential doping, are fabricated by optimizing the fabrication parameters. The fibers are tested in a cladding‐pumped amplifier configuration and their output beam qualities and signal‐to‐noise ratio (SNR) are characterized. The investigation reveals that the fiber with centralized doping in the core region exhibits lower M 2 compared with the fibers with uniform and circumferential doping, as it has a lower overlap of the higher‐order modes with the doped region. The experimental result is further affirmed through theoretically simulated results. The developed fabrication technique shows potential to fabricate specialty fibers of varied designs, where customized doping profiles are required.

Beam quality evolution in large-mode-area specially doped laser fiber through bend-induced effective refractive index change

“…In the PA stage, two types of LMA YDF fibers were used individually-C1 (uniform doped fiber) and C2 (confined doped fiber), whose waveguide parameters are summarized in table 1. The fabrication process and parameters of the LMA YDFs were reported in detail in our previous work [31].…”

“…where n m is the modified RI due to bending, n is the actual RI without bending and R is the bend radius [30]. Two different fibers were considered: C1, having uniform doping over the entire core region, and C2, which is a confined doped fiber where the doping region is confined to 60% of the entire core region to maximize the overlap between the FM and the dopant region [31]. The waveguide parameters of both the fibers are summarized in table 1.…”

Functional Fibers and Functional Fiber-Based Components for High-Power Lasers

“…After the TMI effect was observed experimentally and regarded as the main limiting factor for power scaling of HPFLs, researchers have predicted that the confined-doped fiber is an effective method to improve the TMI threshold of laser system [20] due to the gain tailoring effect among the guided modes. High-power fiber lasers/ amplifiers employing confined-doped ytterbium-doped fiber have made continuous breakthroughs in power scaling and beam quality preservation [35,48,51,52,59,71,[292][293][294][295][296][297][298][299][300][301][302][303][304][305][306][307][308][309] in recent years.…”

“…If the gain fiber is coiled to a tight condition, the mode field distortion caused by fiber bending is likely to weaken the preferential gain effect on the fundamental mode. In this way, bending-resistant design is a conceivable pursuit for the future consideration of confined-doped fibers [304][305][306][307][308][309][310][311][312][313].…”