Tunable Single-, Dual- and Multi-wavelength Fibre Lasers by Using Twin Core Fibre-based Filters

Abstract

Tunable fibre lasers draw intensive attention because their emission wavelength can be systematically tuned within a certain spectral range, which allows using a single laser source instead of several sources. This is convenient and cost-effective for many applications in a range of fields, such as telecom, material processing, microscopy, medicine and imaging and so on. The laser wavelength can be tuned in a certain range of wavelength by inserting wavelength-selective elements into the laser's optical cavity. This chapter describes the twin core fibre (TCF)-based filters, which work as the wavelength-selective element. They are introduced into the ring cavity to implement tunable single-, dual-and multi-wavelength fibre lasers. First, we deduced the coupled-mode theory of TCF-based filter. Second, we experimentally and numerically characterized the optical properties of TCF-based filters including free spectral range, polarization dependence, strain effect and bending effect. Finally, we investigated three tunable fibre lasers which operate at single-, dual-and multi-wavelengths, respectively. The operation mechanism of the fibre lasers mainly involved the elastic-optic effect, polarization hole burning effect and non-linear optical loop mirror. We emphasized the tuning mechanism and the tuning characteristics of the tunable fibre lasers.

Switchable mode-locked ytterbium-doped fiber laser based on macrobending loss tuning of figure-eight knot fiber structure

“…38,39 Also, the effects of cavity loss, properties of the gain medium, polarization hole burning, and filtering effect may be responsible for the randomness of output wavelength interval positions. 40 According to the ability to generate the multiwavelength lasing by elevating the pump power, the switchable multiwavelength generation was examined by constantly controlling the polarization condition inside the ring cavity. The PC is a crucial optical component for modulating the birefringence and generating multiwavelength operation.…”

“…These multiwavelength operations can be attributed to when the excited power increases; more modes will obtain an appropriate gain to override the losses inside the ring cavity 38 , 39 . Also, the effects of cavity loss, properties of the gain medium, polarization hole burning, and filtering effect may be responsible for the randomness of output wavelength interval positions 40 …”