Experimental investigation of the nonlinear optical loop mirror with twisted fiber and birefringence bias

Abstract

We examine the transmission characteristics of a NOLM device using a symmetrical coupler, highly twisted fiber, and a quarter-wave (QW) retarder plate introducing a polarization asymmetry in the loop. We demonstrate high dynamic range with controllable transmissivity, and good stability over long times. We experimentally study the transmission behavior for different input polarization states and distinguish between different polarization components of the output beam. Experiments are in good agreement with our theoretical approach previously published. Appropriate choice of the input and output polarizations allows a very high dynamic range. The adjustment of the QW retarder and input polarization enables tuning the critical power over a wide range.

Large amplitude noise reduction in ultrashort pulse trains using a power-symmetric nonlinear optical loop mirror

“…To prevent the nonlinear polarisation evolution from averaging out for each beam, twist is applied to the fibre, which then becomes optically active and behaves like an ideal isotropic fibre [24]. Starting from the coupled nonlinear differential equations for polarisation evolution in the continuous-wave case [25], a model was proposed in [21], which enabled a thorough study of this promising device (see for example [26][27][28]). In comparison with conventional schemes, the proposed architecture showed up improved robustness to external perturbations, and enhanced flexibility of the transmission characteristic (which can be adjusted through controlling polarisation and birefringence).…”

Symmetric nonlinear optical loop using the nonlinear polarization rotation

“…All the qualities of this NOLM make it a very promising device in particular for applications such as pulse shortening and pedestal suppression, amplitude regularization and relaxation oscillations damping. In our previous works, we suggested the use of the NOLM with symmetrical coupler, highly twisted fiber and a QWR in the loop (to break the polarization symmetry [4]) to be used as saturable absorber. For low input power the NOLM transmission is adjustable as well as the slope of the nonlinear dependence by a simple rotation of the QWR.…”

Symmetric Nonlinear Optical Loop Mirror Used as Saturable Absorber in Mode-Locked Fiber Laser

“…If a symmetrical coupler is used in the loop, the switching can be obtained through the dispersion effect or the dependence of the nonlinear phase shift on polarization. In this paper we make a review of our previous works, in which, we suggested the use of the NOLM with symmetrical coupler, highly twisted fiber and a QWR in the loop (to break the polarization symmetry [4]) to be used as saturable absorber. For low input power the NOLM transmission is adjustable as well as the slope of the nonlinear dependence by a simple rotation of the QWR.…”