Broadband bidirectional Brillouin–Raman random fiber laser with ultra-narrow linewidth

We present a Brillouin–Raman random fiber laser(BRRFL)with full-open linear cavity structure to generate broadband Brillouin frequency comb(BFC)with double Brillouin-frequency-shift spacing.The incorporation of a regeneration portion consisting of an erbium-doped fiber and a single-mode fiber enables the generation of broadband BFC.The dynamics of broadband BFC generation changing with the pump power(EDF and Raman)and Brillouin pump(BP)wavelength are investigated in detail,respectively.Under suitable conditions,the bidirectional BRRFL proposed can produce a flatamplitude BFC with 40.7-nm bandwidth ranging from 1531 nm to 1571.7 nm,and built-in 242-order Brillouin Stokes lines(BSLs)with double Brillouin-frequency-shift spacing.Moreover,the linewidth of single BSL is experimentally measured to be about 2.5 kHz.The broadband bidirectional narrow-linewidth BRRFL has great potential applications in optical communication,optical sensing,spectral measurement,and so on.

Wavelength-interval switchable Brillouin–Raman random fiber laser through Brillouin pump manipulation

A wavelength-interval switchable Brillouin–Raman random fiber laser(BRRFL) based on Brillouin pump(BP) manipulation is proposed in this paper. The proposed wavelength-interval switchable BRRFL has a full-open cavity configuration, featuring multiwavelength output with wavelength interval of double Brillouin frequency shifts. Through simultaneously injecting the BP light and its first-order stimulated Brillouin-scattered light into the cavity, the laser output exhibits a wavelength interval of single Brillouin frequency shift. The wavelength-interval switching effect can be manipulated by controlling the power of the first-order stimulated Brillouin scattering light. The experimental results show the multiwavelength output can be switched between double Brillouin frequency shift multiwavelength emission with a broad bandwidth of approximately 60 nm and single Brillouin frequency shift multiwavelength emission of 44 nm. The flexible optically controlled random fiber laser with switchable wavelength interval makes it useful for a wide range of applications and holds significant potential in the field of wavelength-division multiplexing optical communication.

Wavelength switchable mode-locked fiber laser with a few-mode fiber filter

We have proposed and constructed a few-mode fiber(FMF)-based comb filter realized by dislocation splicing a fewmode long-period fiber grating(FM-LPFG) with a single-mode fiber(SMF). From an all-fiber laser with a FMF-based comb filter, the generation of switchable single-, dual-, triple-, and quadruple-wavelength continuous light has been achieved.Moreover, wavelength switchable mode-locked pulses have been obtained with the increased pump power. In the experiment, the output wavelength of the mode-locked fiber laser was changed from 1567.72 nm to 1571.04 nm, while the signal-to-noise(SNR) ratio was maintained above 61 d B. The switchable multiwavelength continuous wave(CW) and mode-locked all-fiber lasers have potentially important applications for fiber sensing, wavelength-division multiplexing(WDM) and signal processing.

Spatiotemporal mode-locked multimode fiber laser with dissipative four-wave mixing effect

The high degree of freedom and novel nonlinear phenomena of multimode fiber are attracting attention. In this work,we demonstrate a spatiotemporal mode-locked multimode fiber laser, which relies on microfiber knot resonance(MKR) via dissipative four-wave-mixing(DFMW) to achieve high-repetition-rate pulses. Apart from that, DFMW mode locking with switchable central wavelengths can also be obtained. It was further found that high pulse energy induced nonlinear effect of the dominant mode-locking mechanism transforming from DFMW to nonlinear Kerr beam cleaning effect(NL-KBC). The experimental results are valuable for further comprehending the dynamic characteristics of spatiotemporal mode-locked multimode fiber lasers, facilitating them much more accessible for applications.

Reversible generation of dissipative Kerr solitons in a microresonator by the backward tuning method

Soliton generation schemes have attracted considerable scholarly attention.This paper introduces a novel backward tuning method for the reversible generation of dissipative Kerr solitons(DKSs).Reversible soliton generation relies on the thermal stabilization of the auxiliary laser,coupled with backward tuning of the pump laser,significantly increasing the range of soliton steps by over 10 times.Moreover,the method alleviates the stringent auxiliary laser detuning requirement.By adjusting the detuning of the auxiliary laser,diverse numbers of solitons can be deterministically generated,enhancing both flexibility and precision.

Mode field switching in narrow linewidth mode-locked fiber laser

Acousto-optic interaction can be used for ultrafast optical field control in passively mode-locked fiber lasers.Here,we propose the use of an intracavity acousto-optic mode converter (AOMC) with combination of a few-mode fiber Bragg gratings (FM-FBG) to achieve narrow linewidth mode-locked pulse output with switchable transverse mode and wavelength in a ring fiber laser.Due to the selectivity of the FM-FBG to the input mode,the output mode and wavelength can be adjusted in the mode-locked fiber laser based on a semiconductor saturable absorption mirror.In experiments,by adjusting the acoustic frequency imposed in the AOMC,the wavelength of mode-locked pulses was switched from 1551.52 nm to 1550.21 nm,retaining the repetition rate of 12.68 MHz.At the same time,the mode conversion from the LP;to the LP;mode in the FM-FBG transmission port was achieved.This laser may find application in mode-division multiplexing systems.

Mode-locked pulse generation from an all-FMF ring laser cavity

Experimental generation of stable mode-locked pulses and cylindrical vector beams(CVBs),from an all fewmode fiber(FMF)ring laser is first reported,to the best of our knowledge.In this laser,a section of few-mode erbium-doped fiber(FM-EDF)is used as the gain medium.The FM-EDF is pumped by 976nm laser with LP11 mode,which is simultaneously converted and multiplexed through a homemade hybrid device,i.e.,wavelength division multiplexing-mode selection coupler(WDM-MSC).All the components in our experiment are connected using FMF.The resulted CVB pulses have a spectral width of 0.33 nm with a repetition rate of 30.58 MHz under the pump power of 340 m W.Moreover,both azimuthally and radially polarized CVBs were achieved with a high purity of>95%.This mode-locked CVB fiber laser with an all FMF configuration opens the way to manipulate the transverse mode in mode-locked fiber lasers.

Improvement on refractive index sensing by exploiting the tapered two-mode fibers

The spectral characteristics and sensitivities of a tapered two-mode fiber sandwiched between two single-mode fibers are systematically investigated. Theoretical calculations reveal that a dispersion turning point(DTP)appears when the group effective refractive index(RI) difference between the fundamental mode and the higher-order mode equals zero;as a result, ultrahigh RI sensitivities can be achieved. Furthermore, the location of the DTP is strongly dependent on the tapering condition. Then, we experimentally demonstrate high sensitivities of the RI sensor with the waist diameter of 4 μm by means of immersing it in a flow cell filled with glycerol solution. In further tracking of the resonant wavelength shift around the DTP, it is found that the proposed RI sensor exhibits a sensitivity of 1.81 × 104 nm/RIU and a limit of detection down up to 3.29 × 10-5 RIU in a liquid glycerol solution.