High-brightness all-fiber Raman lasers directly pumped by multimode laser diodes

S A Babin

doi:10.1017/hpl.2018.76

Abstract

High-brightness fiber laser sources usually utilize active rare-earth-doped fibers cladding-pumped by multimode laser diodes (LDs), but they operate in limited wavelength ranges. Singlemode-passive-fiber based Raman lasers are able to operate at almost any wavelength being pumped by high-power fiber lasers. One of the interesting possibilities is to directly pump graded-index (GRIN) multimode passive fibers by available high-power multimode LDs at 915–940 nm, thus achieving high-power Raman lasing in the wavelength range of 950–1000 nm, which is problematic for rare-earth-doped fiber lasers. Here we review the latest results on the development of all-fiber high-brightness LD-pumped sources based on GRIN fiber with in-fiber Bragg gratings (FBGs). The mode-selection properties of FBGs inscribed by fs pulses supported by the Raman clean-up effect result in efficient conversion of multimode pump into a high-quality output beam at 9xx nm. GRIN fibers with core diameters 62.5, 85 and $100~\unicode[STIX]{x03BC}\text{m}$ are compared. Further scaling capabilities and potential applications of such sources are discussed.

Highlights

High-brightness fiber laser sources based on active rareearth (RE)-doped fibers are characterized by excellent output characteristics and unique performance enabling their wide use for scientific and industrial applications[1]
We have demonstrated possibilities to develop highbrightness 9xx-nm fiber sources based on the passive MM GRIN fiber directly pumped by high-power MM laser diodes (LDs)
Allfiber configuration of such diode-pumped Raman fiber lasers (RFLs) is shown to be possible with the use of fiber Bragg gratings (FBGs) inscribed in the MM GRIN-fiber core and LD coupling via spliced fiber pump combiner

Summary

Introduction

High-brightness fiber laser sources based on active rareearth (RE)-doped fibers are characterized by excellent output characteristics and unique performance enabling their wide use for scientific and industrial applications[1]. Using for pumping the most powerful Yb-doped fiber laser (YDFL) operating around 1 μm, it is possible to obtain Raman lasing almost in the whole transmission window of silica fibers (1–2 μm), thanks to the efficient cascaded generation of higher-order Stokes components. In their turn, high-power RE-doped fiber lasers are usually cladding-pumped by multimode (MM) laser diodes (LDs). Further scaling capabilities and potential applications of such sources are discussed

Experimental scheme and operating principles

Raman lasing in GRIN fibers of different core diameters

Random Raman lasing in GRIN fibers

Findings

Conclusion