2-μm switchable, tunable and power-controllable dual-wavelength fiber laser based on parallel cavities using 3 × 3 coupler

Abstract

play a great role in the lidar, spectroscopy analysis and distributed optical fiber sensing [1][2][3]. Of these multiwavelength fiber lasers, the fiber lasers around 2 μm can achieve potential applications in atmospheric transmission, gas sensing, lidar and new wavelength-divisionmultiplexed fiber communication systems [4][5][6]. Hence, the research of switchable narrow linewidth multi-wavelength fiber ring lasers around 2 μm has significance to the above fields.Switchable multi-wavelength fiber lasers mainly employ overlap cavities or polarization hole burning (PHB) to control or adjust the properties of wavelength, and therefore to achieve wavelength switching. Corresponding to the properties, various methods have been proposed and reported, such as cascaded FBGs [7], highly birefringent (Hi-Bi) fiber loop mirrors [8], Sagnac loop mirror [9], fiber Bragg gratings (FBGs) written in Hi-Bi fibers [10,11], acoustic waves [12], spatial mode beating of multimode fiber [13] and cascaded filter structures [14]. However, multi-wavelength lasers in some special applications require the specific wavelength to be tunable or controllable, for instance, switching from one lasing line to another or two lasing lines at the same time. For example, this laser can be tuned and switched to the specific absorption wavelengths of some certain gases in multi-gases sensing application [15], or to the transmit window in atmospheric transmission application [16]. The laser topology based on the combination of the FBGs and ultra-narrow bandwidth phase-shifted FBGs using optical circulator is an effective method to achieve switchable multi-wavelengths; however, it is complex, costly and not tunable [17].In this paper, a switchable, tunable and power-controllable dual-wavelength Tm-Ho co-doped fiber laser (THCDFL) around 2 μm is proposed and experimentally Abstract We demonstrate a switchable, tunable and power-controllable dual-wavelength fiber laser in 2-μm region based on parallel cavities using a 3 × 3 coupler. The laser topology is based on the parallel connection of fiber Bragg gratings (FBGs) using 3 × 3 coupler which act as two individual cavities, so that the dual wavelengths are tunable and switchable by adjusting the center wavelengths of FBGs and the cavity losses, respectively. With suitable cavity losses and input pumping power, we can obtain a 2-μm switchable single-or dual-wavelength fiber laser. The proposed configuration has very good application prospects in the fields of atmospheric transmission, gas sensing, lidar and new wavelength-division-multiplexed fiber communication systems.

Tunable dual-wavelength operation of an all-fiber thulium-doped fiber laser based on tunable fiber Bragg gratings

“…Different techniques have been proposed to reduce the competition based on the adjustment of intra-cavity losses. These techniques include the use of optical fiber devices such as polarization controllers (PCs) [7,8], variable optical attenuators (VOAs) [9], optical fiber interferometers [10][11][12][13], and narrow bandwidth filters [14].…”

Tunable Dual-Wavelength Thulium-Doped Fiber Laser Based on FBGs and a Hi-Bi FOLM

“…Recently, different dualwavelength TDFLs approaches at the 2-μm wavelength band were reported. These configurations are based on fiber Bragg Gratings (FBG) [1]- [9], spatial mode beating effect [10]- [12], carbon nanotubes [13], photonic crystal fibers [14], and fiber interferometers [1], [15]- [17], among others. Liu of a TDFL based on a polarization maintaining (PM) FBG and a PM Fabry-Perot filter [1].…”

“…In order to improve the stability of the simultaneously generated laser lines of TDFLs, different techniques for the intracavity losses adjustment have been proposed [1]- [13]. These techniques are based on the use of polarization controllers (PCs) [1]- [7], [10]- [13] and variable optical attenuators [8]- [9]. However, in the proposed techniques a rough and arbitrary adjustment of the intracavity losses is performed which reduces the repeatability and the stability of the dual-wavelength laser generation.…”

High-power dual-wavelength Ho-doped fiber laser at >2 μm tandem pumped by a 1.15 μm fiber laser

“…With the rapid development of 2 μm fiber-based devices and high-power pump sources, the power records of Tm- and Ho-doped silica fiber lasers operating at 2 μm have reached hundred- to kilo-watt level 7 8 9 . Besides these remarkable milestones, fiber laser techniques to achieve dual-wavelength lasing at 2 μm are also under considerable research, due to the prospective applications in the fields including next-generation optical fiber communication networks, ranging systems, spectroscopy, terahertz generation and mitigating stimulated Brillouin scattering effects in fiber amplifiers 10 11 12 13 14 15 16 17 .…”

“…Rapid progress of 2 μm dual-wavelength fiber lasers has been made in recent years. Different approaches have been employed in continuous-wave (CW) Tm- or Tm-Ho-co-doped fiber lasers to obtain stable dual-wavelength lasing, including techniques based on volume Bragg gratings 10 , coupled laser cavities with cascaded fiber Bragg gratings (FBGs) 11 12 , polarization hole burning by the means of high-birefringence fiber Bragg gratings (HB-FBGs) 13 or birefringence gain medium 14 , cascaded filter 15 , parallel connection of FBGs by using coupler 16 , using photonic crystal fiber (PCF) 17 and multi-mode non-adiabatic taper fiber as wavelength-selective filter. While for pulsed fiber lasers at 2 μm, carbon nanotube (CNT) saturable absorber 18 and nonlinear optical loop mirror (NOLM) 19 have been employed in passive mode-locked fiber lasers to generate dual wavelengths.…”