Reconfiguration of the multiwavelength operation of optical fiber ring lasers by the modifiable intra-cavity induced losses of an in-fiber tip probe modal Michelson interferometer

Abstract

A straightforward and versatile method for switching from single to different multiwavelength laser emission in ring cavity fiber lasers is proposed and demonstrated experimentally. The method is based on using the changeable interference pattern from an optical fiber modal Michelson interferometer as a wavelength selective filter into the ring cavity laser. The interferometer is constructed using a bi-conical tapered fiber and a single-mode fiber segment, with these being spliced together to form an optical fiber tip probe. When the length of the single-mode fiber piece is modified, the phase difference between the interfering modes of the interferometer causes a change in the interferometer free spectral range. As a consequence, the laser intra-cavity losses lead to gain competition, which allows us to adjust the number of simultaneously generated laser lines. A multiwavelength reconfiguration of the laser from one up to a maximum of eight emission lines was obtained, with a maximum SNR of around 47 dBm.

Erbium Ring Fiber Laser Cavity Based on Tip Modal Interferometer and Its Tunable Multi-Wavelength Response for Refractive Index and Temperature

“…Moreover, the fiber laser arrangement can be used for remote sensing applications. Despite the power instabilities observed, the laser offers better performance than some works [14,18]. The laser presented in this work is an alternative, cost-effective setup for tuning multi-wavelength spectra using simple and easy-to-control techniques.…”

“…All these features prevent crosstalk, error measurement, and low resolution. To this end, many methods have been proposed, most of them based on fiber interferometers (Fabry-Perot, Mach-Zehnder, Michelson, and Sagnac) [15][16][17][18][19], comb filters [20,21], Raman effect [20], Brillion scattering [22,23], nonlinear loop mirrors [24], saturable optical absorber elements [25,26], and extrinsic interferometers [27].…”

Wavelength switching and tuning of fiber lasers by using a modifiable intra-cavity filter based on a modal Michelson interferometer

“…As the light is launched into the core fiber input in port 1, it goes to the OC port 2. At the tapered fiber, a portion of light from the core mode is coupled to the higher order cladding mode [34,35] in the L SMF piece. Then, by the Fresnel reflection, both modes (core and cladding mode) are reflected in the planar end face of the SMF.…”

“…So, the generated phase difference between modes for every wavelength depends on the different effective refractive indexes of the core and cladding propagated modes. The phase difference can be approximately calculated by [35][36][37][38]: where λ is the wavelength of the core and cladding mode, L is the SMF piece length, n effcore is the effective refractive index of the core mode corresponding to the wavelength λ, and n effcladding is the effective refractive index of the cladding mode corresponding to the wavelength λ.…”

Switchable Ytterbium Fiber Laser Based on a Symmetrical Long-Period Fiber Grating

“…In an arrangement based on FBGs, the number of switchable wavelengths requires an equal amount of FBGs [30]. On the other hand, a remarkable variety of WSFs are based on interferometers such as Mach-Zehnder [35]- [38], Fabry-Perot [39] or Michelson [40], [41] and long-period fiber grating (LPFG) [42]. In all the above studies, a crucial challenge to achieve a switchable MWFL operation is given by the strong mode competition and unstable laser output [43], [44] caused by the homogeneous gain broadening of the rare-earth doped fiber gain medium [45].…”