Intrinsic amplitude-noise suppression in fiber lasers mode-locked with nonlinear amplifying loop mirrors

Abstract

In this Letter, we investigate steady states of fiber lasers mode-locked with a nonlinear amplifying loop mirror that have an inherent amplitude-noise-suppression mechanism. Due to the interaction of the sinusoidal transmission function with the fluctuating intracavity pulse amplitude, we show that under specific preconditions, this mechanism may lead to a detectable difference in relative intensity noise at the reflected and transmitted output port of the laser. We present systematic intensity noise measurements with a nonlinear fiber-based system that replicates a single roundtrip in the laser cavity. The experimental results and simulations clearly show a reduction of the intracavity amplitude fluctuations up to 4 dB for certain steady states.

Large-mode-area soliton fiber oscillator mode-locked with linear self-stabilized Sagnac-interferometer

“…This noise difference is characteristic for fiber oscillators mode-locked with nonlinear fiber interferometers and can be explained with the dynamic response of the SA transmission T(∆φ nl ) to the intensity-fluctuations of the intracavity pulse and thus in agreement with our study summarized in Ref. [26]. In conclusion, we demonstrated an investigated an Yb-doped all-PM fiber oscillator mode-locked with a self-stabilized Sagnacinterferometer that uses a 25 µm core LMA fiber to avoid excessive nonlinear phase-shifts while scaling up the energy.…”

Nonlinear fiber system for shot-noise limited intensity noise suppression and amplification

“…In addition, unbalanced net cavity dispersion directly converts center frequency fluctuations into timing fluctuations [14], a phenomenon known as Gordon-Haus effect [15]. To a certain extent, the influence of these effects can be minimized for example through precise dispersion-engineering [16], by optimizing the cavity loss [12] or by utilizing inherent noise suppressing mechanisms provided by the saturable absorber [17]. Further reduction of the noise far beyond those limitations requires modifications of the cavity, e.g., with an implementation of tailored spectral reshaping with bandpass filters [18,19] or the application of electronic feedback loops for a modulation of the pump source [20].…”

“…Hence, the conversion of peak power fluctuations P=P ̅ +δP(t) into fluctuations of the nonlinear phase difference ∆φ nl =∆φ nl ̅̅̅̅̅̅ +∆φ nl (t) couples the system transmission with the input intensity fluctuations. For the case of a negative derivative at T(∆φ nl ̅̅̅̅̅̅ ) and a positive sign of ∆φ nl ̅̅̅̅̅̅ , the transmission response of the system results in an effective suppression of the input noise [17]. Depending on the energy splitting ratio 𝜀, even vanishingly low input fluctuations δP(t) can be converted to large corresponding values of ∆φ nl (t) inducing a strong effect of the system transmission response.…”

“…The simulation is based on the model described in Ref. [17] with an input average peak power of P ̅ =1kW and a fluctuation δP of ±1%. The fiber segment consists of a 2-m long fiber with the parameters of standard 1 µm PM-fibers (Nufern PM980-XP).…”

Dispersion management of a nonlinear amplifying loop mirror-based erbium-doped fiber laser

“…The advantage of the presented system was the use of one of the output ports for distance measurement (transmitted), while the reflective port was used for monitoring [44]. A novel simulational and experimental study on steady-state NALM fiber oscillator with both transmitted and reflected output ports has revealed a relationship between the transmission function and fluctuation of the intracavity pulse peak power that leads to amplitude-noise suppression in the transmitted output port [45]. Additionally, NALM has been shown as a mode-locker in various dual-wavelength mode-locked fiber lasers incorporating Sagnac loop filter [46], polarization multiplexing [47], and mechanical spectral filtering [33].…”