Ytterbium-doped large-mode-area all-solid photonic bandgap fiber lasers

Abstract

Single-mode operation in a large-mode-area fiber laser is highly desired for power scaling. We have, for the first time, demonstrated a 50μm-core-diameter Yb-doped all-solid photonic bandgap fiber laser with a mode area over 4 times that of the previous demonstration. 75W output power has been generated with a diffraction-limited beam and an efficiency of 70% relative to the launched pump power. We have also experimentally confirmed that a robust single-mode regime exists near the high frequency edge of the bandgap. These fibers only guide light within the bandgap over a narrow spectral range, which is essential for lasing far from the gain peak and suppression of stimulated Raman scattering. This work demonstrates the strong potential for mode area scaling of in single-mode all-solid photonic bandgap fibers.

Demonstration of ultra-low NA rare-earth doped step index fiber for applications in high power fiber lasers

“…However, non-linear effects often found to be the primary limiting factors for power scaling in fiber lasers and amplifiers [3]. Several fiber designs such as Photonic Crystal Fiber (PCF) [4], Leakage Channel Fiber (LCF) [5], Resonantly-enhanced Leakage Channel Fiber (Re-LCF) [6], Bragg fiber [7], 2D-All Solid Photonic Bandgap Fiber (2D-PBGF) [8], Polygonal Chirally Coupled Core (P-CCC) [9], bend compensated Parabolic Fiber [10], Multi trench Fiber (MTF) [11][12][13][14], and Pixelated Trench Fiber (PTF) [15] have been proposed to scale the effective area of the fundamental mode (FM) in order to increase the threshold of non-linear effects. However, most of these fiber designs such as PCF, LCF, Re-LCF, and 2D-ASPBGF are difficult to fabricate compared to SIF as they require stack and draw process due to their noncircular symmetry.…”

Specialty fibers for high power lasers and amplifiers

“…In addition, LMA fiber designs should also offer other features such as effective single mode operation to ensure good output beam quality, bend robustness, and easy cleaving and fusion splicing. Over the past few years, different LMA fiber designs have been proposed such as photonic crystal fiber (PCF) [4], leakage channel fiber (LCF) [5], Polygonal-chirally coupled core fibers (P-CCC) [6], and photonic bandgap based fibers such as 2D-all solid photonic bandgap fiber (2D-ASPBGF) [7] and Bragg fiber [8]. However, most of these designs do not offer delocalization of the higher order modes (HOMs) and mostly rely on loss of the HOMs.…”

Extending single mode performance of all-solid large-mode-area single trench fiber

“…Over the past decade, there have been numerous research efforts across the globe to find out optimum fiber designs which can offer effective single mode operation (ESM) with very large mode area (LMA). Several fiber designs have been proposed to meet ESM operation by offering high loss to the higher order modes (HOMs) such as low numerical aperture step index fiber (low NA-SIF) [4], photonic crystal fiber (PCF) [5] based designs such as leakage channel fiber (LCF) [6], resonantly enhanced leakage channel fiber (Re-LCF) [7], and hybrid photonic crystal fiber (H-PCF) [8], photonic bandgap based fiber such as Bragg fiber [9] and 2D-all solid photonic bandgap fiber (2D-ASPBGF) [10], and resonant coupling based design such as polygonal chirally coupled core fiber (P-CCC) [11]. These designs are mostly engineered in such a way that at a practical bend radius of 10-20cm, HOMs can be suppressed by using bend induced and design based leakage loss to them.…”

“…Most of these fiber designs such as PCF [5], LCF [6], Re-LCF [7], H-PCF [8], 2D-ASPBGF [10], and P-CCF [11] are difficult to fabricate because they require stack and draw process due to non-circular fiber symmetry. Moreover PCF [5], LCF [6], Re-LCF [7], H-PCF [8], Bragg fiber [9], and 2D-ASPBGF [10] require the refractive index of core and cladding to be same, which is really challenging to achieve as core of active fiber needs doping with rare earth ions and co-dopants for fiber laser operation and unfortunately these dopants are refractive index raising materials.…”

“…Moreover PCF [5], LCF [6], Re-LCF [7], H-PCF [8], Bragg fiber [9], and 2D-ASPBGF [10] require the refractive index of core and cladding to be same, which is really challenging to achieve as core of active fiber needs doping with rare earth ions and co-dopants for fiber laser operation and unfortunately these dopants are refractive index raising materials. Hence, in order to match the refractive index of actively doped core and cladding, active core is doped with additional co-dopants to reduce the core refractive index.…”