Wavelength tuning of fiber lasers using multimode interference effects

R Selvas,E G Johnson,D A May-Arrioja,I Torres-Gomez,A Mehta,P Likamwa,A Martinez-Rios,J A Alvarez-Chavez

doi:10.1364/opex.13.009439

Abstract

We report on a novel scheme to fabricate a simple, cheap, and compact tunable fiber laser. The tuning is realized by splicing a piece of single-mode fiber to one end of an active double-clad fiber, while the other end of the single-mode fiber is spliced to a 15 mm long section of 105/125 multimode fiber. The fluorescence signal entering into the multimode fiber will be reproduced as single images at periodic intervals along the propagation direction of the fiber. The length of the multimode fiber is chosen to be slightly shorter than the first re-imaging point, such that the signal coming out from the single mode fiber is obtained in free space, where a broadband mirror retroreflects the fluorescence signal. Since the position of the re-imaging point is wavelength dependent, different wavelengths will be imaged at different positions. Therefore, wavelength tuning is easily obtained by adjusting the distance between the broadband mirror and the multimode fiber facet end. Using this principle, the tunable fiber laser revealed a tunability of 8 nm, ranging from 1088-1097 nm, and an output power of 500 mW. The simplicity of the setup makes this a very cost-effective tunable fiber laser.

Highlights

Considerable interest has been shown in the development of cladding pumped fiber lasers (CPFLs) because of their exceptional characteristics for practical applications
It can be noticed that for separation distances shorter than 100 micron and longer than 250 microns the lasing emission vanished and does not correlate to the emission cross section spectrum of the Yb ions. This was related to different factors such as the use of a broadband mirror that was not optimized for this particular wavelength range, and additional excessive loss generated in the singlemode fiber (SMF)-multimode fiber (MMF) splice point (>3 dB)
We have investigated the performance of a novel tuning mechanism that operates by employing the self-imaging properties of MMF

Summary

Introduction

Considerable interest has been shown in the development of cladding pumped fiber lasers (CPFLs) because of their exceptional characteristics for practical applications. The second important consideration is to improve the pump absorption so that skew rays do cross through the core This issue has been approached by varying the geometry of the inner cladding of the fiber to effectively reduce the fiber length by increasing the absorption [2]. Due to the wavelength dependence of the re-image, the position of the re-imaging plane will depend on the wavelength, and the laser wavelength can be tuned by varying the distance between the MMF facet and the broadband mirror Using this principle, the tunable fiber laser revealed a tunability of 8 nm, ranging from 1088-1097 nm, and an output power of 500 mW. The simplicity of the setup makes this tunable laser very cost-effective

Tuning mechanism

Experimental layout and results

Conclusions