Yb/Er co-doped phosphate all-solid single-mode photonic crystal fiber

Abstract

An all-solid Yb 31 /Er 31 co-doped single-mode phosphate photonic crystal fiber (PCF) with Watt-level output power and 20 mm core diameter is demonstrated for the first time. A PCF whose refractivity of the active core is lower than that of the background glass is suggested and theoretically confirmed to be in single-mode operation at 40 mm core diameter.F ibers with short length and large mode area (LMA) are some of the most extensively investigated subjects in high-power fiber lasers and amplifiers 1 . On one hand, LMA fibers can withstand considerably higher energy without end-face damage and can effectively increase the threshold of nonlinear effects. Many solutions have been suggested to overcome the limitation of the core diameter in a traditional step-index fiber, including chirally-coupled-core (CCC) fibers 2 , leaky channel fibers 3 , gain-guiding fibers 4 , all-solid photonic bandgap fibers 5 , and so forth. Among them, photonic crystal fibers (PCFs) 6,7 are some of the most promising designs for extending the core diameter of a single-mode LMA fiber. In fact, LMA-PCFs with core sizes approaching 100 mm have already been demonstrated 8 , thereby indicating the scalability of the core diameter in this kind of design. However, the presence of hollows in a traditional LMA-PCF causes difficulty in splicing PCFs to commercially available fiber-coupled devices and thus realizing an all-fiber laser system. Consequently, the industrial applications of LMA-PCFs are limited. To address this problem, a PCF with an all-solid (AS) microstructure has been suggested and realized 9 . The hollows of this PCF are replaced by another kind of glass, making the all-fiber laser system possible. After then, an Nd-doped silicate AS-PCF 10 and a single-mode Nd-doped phosphate AS-PCF with up to 40 mm core diameter are realized 11 .On the other hand, a short-length fiber can weaken the nonlinear effects and make a laser system more compact. A straightforward method of shortening fiber length is to heavily dope the active core. However, for the extensively used silica PCFs 12,13 , the solubility of rare-earth ions such as Yb 2 O 3 cannot be substantially increased prior to the onset of other deleterious effects, such as quenching, phase separation, and devitrification 14,15 . In addition, when the core is highly doped, matching the refractive indexes between the photonic crystal cladding and the active core is difficult for silica glass, which decreases the core diameter scalability of the PCF. By contrast, soft glass can be very heavily doped without exerting any other detrimental effect 16 , and its refractive indices can be easily adjusted. Thus, soft glass is a promising medium for PCF 17,18 .In this paper, we demonstrate for the first time a phosphate Yb/Er co-doped single-mode AS-PCF with Wattlevel output power and 20 mm core diameter. Using the finite-difference time-domain method, we also confirm that a single-mode AS-PCF with up to 40 mm core diameter can be realized using an index-depressed active core based on the conc...

High Glass Transition Temperature Barium Silicophosphate Glasses Designed with Topological Constraint Theory

“…5,6 However, the further applications of laser glasses and optical fibers require phosphate glasses with a higher refractive index and optimized mechanical properties. 1,[7][8][9] Previous researches suggest that the introduction of SiO 2 could increase the refractive index and improve the mechanical properties of phosphate glasses. 10 But, it introduces some complex glass network structures, 11 which increases the difficulty on the research on the structure and properties of glasses.…”

Ion-Doped Photonic Crystal Fiber Lasers

“…For example, in their study of large-mode field photonic crystal fiber lasers, Wang et al (2017) successfully prepared a fiber with a core diameter of 50 μm using Yb 3+ /Al 3+ /P 5+ /F − co-doping and achieved a laser output with an average power of 97 W, a peak power of 93 kW, and a beam quality of 1.4. Since high-power fiber lasers in the 1.5 µm band have a wide range of applications and the gain medium for fiber lasers in this band is usually a double-clad erbium-ytterbium co-doped fiber, so that ytterbium-erbium co-doped photonic crystal fibers dominate among other dopant ions, Of which Wang et al (2014) studied large-mode field fiber lasers using erbium-ytterbium co-doping in a stable laser output with a maximum power of 1.6 W and a center wavelength of 1,534.5 nm obtained in a 600 mm length photonic crystal fiber. The pump optical power was 150 mW, with the slope efficiency of 21%, and the beam quality factor M 2 less than 1.05.…”

Large-mode-area single-mode-output Neodymium-doped silicate glass all-solid photonic crystal fiber

“…Moreover, the control of the fiber parameters during the drawing process is much simpler and the development of parameters similar to the designed ones is straightforward. Recently, there are some studies about all solid large mode area single mode phosphate glass fiber 14 15 , but it seems that it was difficulty to get the single mode when the fiber core diameter exceed 40 μm. As we know, it’s the first time realize a 45 μm core diameter single mode laser output in the all-solid Neodymium-doped (Nd-doped) silicate glass photonic crystal fiber.…”