Setting Of Polarization Controller Research Articles

Group-velocity-locked vector solitons and dissipative solitons in a single fiber laser with net-anomalous dispersion

Laser cavities which can generate different types of ultrashort pulses are attractive for practical applications and the study of pulse dynamics. Here, we report the first experimental observation of both conventional solitons (CS) and dissipative solitons (DS) generated from a single all-fiber laser with net-anomalous dispersion. A birefringence-related intracavity Lyot filter with an adjustable extinction ratio enables the switching between the two types of ultrashort pulses. Depending on the polarization controller settings and the pump power, either chirp-free CS with a pulse energy of 406 pJ and a spectral bandwidth of 5.1 nm or up-chirped DS with a pulse energy of 5.1 nJ and an optical bandwidth of 9.6 nm can be generated. Similar polarization features are observed when the laser switches between different soliton operations as both CS and DS are group-velocity-locked vector solitons. Our work paves a novel way to generate dissipative solitons with a relatively high pulse energy (one order of magnitude larger than for CS) and a large chirp directly from an all-fiber net-anomalous-dispersion cavity through birefringent filter management.

Ultrashort pulse formation from a thulium-doped fiber laser: Self-characterization and mapping

We have performed an automatic characterization of a mode-locked thulium-doped fiber laser in soliton regime based on a versatile scheme of nonlinear polarization rotation (NPR) mode-locking. The cavity includes three fiber loop waveplates for adjusting the oscillation states of the cavity. The polarization controllers are equipped with servo motors that allow for automated stepping through a large number of polarization controller settings. The optical spectra and the radio frequency spectra of the cavity output are recorded at each polarization controller setting to extract key laser parameters from the data, automatically. Analyzing the large data sets, not only provides maps of the laser operation in various modes, but also it identifies the polarization controller settings leading to optimal mode-locking, consequently. Such method allows a detailed self-characterization of the fiber laser cavity which paves the way to achieve smart fiber lasers. This approach facilitates applications of fiber lasers and improves their reliability for practical purposes, where environmental instabilities might limit their performances.

Experimental Study on Soliton Rain Patterns in Yb-Doped All-Fiber Standing Wave Cavity Configuration

We demonstrate for the first time, experimental observation of soliton rain (SR) state at relatively low pumping power in Yb-doped fiber laser in all-fiber standing wave cavity configuration. SR is shown to be controllable in terms of speed, density, and direction of drifting. Other SR states, such as stationary SR, cyclic SR, and harmonic SR, were also observed by adjusting polarization controller settings. We carefully identified the portion of the spectra contributing to the SR state and correlate its influence on the speed and direction of rain drift relative to the condensed phase. Observation of SR in our cavity can help in enhancing the understanding of dissipative soliton dynamics in all normal dispersion fiber lasers.

Switchable dual-wavelength fiber laser mode-locked by carbon nanotubes

We have proposed a switchable mode-locked fiber laser by means of carbon nanotube saturable absorber and fiber Bragg gratings (FBGs). The single-wavelength mode-locking operation can be switched between 1549.5 and 1559.5 nm, respectively, which correspond to the central wavelengths of two FBGs. With the appropriate setting of polarization controller, the stable dual-wavelength operation can be achieved due to the high stability of saturable absorber based on carbon nanotubes. Our method provides a simple, stable, low-cost, dual-wavelength ultrafast-pulsed source.

Dual-wavelength switchable erbium-doped fiber ring laser based on merged sagnac and intermodal interferences in sagnac loop mirror

A simple but novel concept of switchable dual-wavelength erbium-doped fiber ring laser is proposed and experimentally demonstrated. It is based on a Sagnac loop mirror incorporating a high birefringence few-mode fiber and polarization controller (PC). Since its transmission properties depend on the PC state, the proposed fiber ring laser can operate in the random combination of two wavelengths by adjusting only the PC settings. The potential lasing lines are determined by simultaneous occurrence of the Sagnac and intermodal interferences in the Sagnac loop mirror. All lasing emissions have the optical signal to noise extinction ratio higher than 45 dB and their power fluctuations lower than 0.5 dB.