We theoretically and experimentally demonstrated an all-fiber, hundred-watts-level, linearly-polarized, narrow spectral linewidth laser amplifier at a central wavelength of 1018 nm based on master oscillator-power amplifier configuration, which is composed of a laser oscillator and one stage of the fiber amplifier. The laser system can generate 104-W output power with 3- and 20-dB spectral linewidth of ∼0.073 and ∼0.25 nm, respectively, and a higher polarization extinction ratio of ∼17.89 dB at 1018.3 nm was obtained. Theoretical analysis based on the rate equations was used to optimize the parameters of 1018-nm ytterbium-doped fiber laser system for the maximum suppression of amplified spontaneous emission (ASE). The ASE was well depressed based on the optimization for the parameters of the laser system including the seed power, seed spectrum, gain fiber length in the amplifier, etc. And ∼ 27-dB signal-to-noise ratio was achieved at the maximum output power. The slope efficiency for the amplifier stage can reach 79%, and near-diffraction-limited beam quality ( and ) was obtained.
We demonstrate an all-fiberized, linear-polarized, narrow spectral linewidth laser system with kilowatts-level output power at 1030 nm in master oscillator-power amplifier (MOPA) configuration. The laser system consists of a linear-polarized, narrow linewidth (~28 GHz) fiber laser oscillator and two stages of linear-polarized fiber amplifiers. A 925 W linear-polarized fiber laser with a polarization extinction ratio (PER) of 15.2 dB and a spectral width of ~60 GHz at the central wavelength of 1030.1 nm is achieved. Owing to the setting of the appropriate parameters for the laser, no indication of Stimulate Brillouin Scattering (SBS) is observed in the system. Moreover, thanks to the excellent quantum efficiency of the laser and the thightly coiling of the active fiber in the main amplifier, the mode instability (MI) is successfully avoided. As a result, the near diffraction-limited beam quality (M2<1.3) is achieved.
We report a high-energy (∼97 μJ), high-peak power (∼20 kW), single-frequency, linearly polarized, near diffraction-limited (M2<1.2) ∼4.8-ns pulsed laser source at 775 nm with a 260-Hz repetition rate. This laser was achieved by frequency doubling of a high-energy linearly polarized all-fiber-based master oscillator–power amplifier, seeded by a single-frequency semiconductor distributed feedback laser diode at 1550 nm. The frequency doubling is implemented in a single-pass configuration using a periodically poled lithium niobate crystal, and a conversion efficiency of 51.3% was achieved.
We report a single frequency, linearly polarized, near diffraction-limited, pulsed laser source at 775 nm by frequency doubling a single frequency nanosecond pulsed all fiber based master oscillator-power amplifier, seeded by a fiber coupled semiconductor DFB laser diode at 1550 nm. The laser diode was driven by a pulsed laser driver to generate ~ 5 ns laser pulses at 260 Hz repetition rate with ~ 50 pJ pulse energy. The pulse energy was boosted to ~ 200 μJ using two stages of core-pumped fiber amplifiers and two stages of cladding-pumped fiber amplifiers. The multi-stage synchronous pulse pumping technique was adopted in the four stages of fiber amplifiers to mitigate the ASE. The frequency doubling is implemented in a single pass configuration using a periodically poled lithium niobate (PPLN) crystal. The crystal is 3 mm long, 1.4 mm wide, 1 mm thick, with a 19.36 μm domain period chosen for quasi-phase matching at 33°C. It was AR coated at both 1550 nm and 775 nm. The maximum pulse energy of ~ 97 μJ was achieved when ~ 189 μJ fundamental laser was launched. The corresponding conversion efficiency is about 51.3%. The pulse duration was measured to be 4.8 ns. So the peak power of the generated 775 nm laser pulses reached ~20 kW. To the best of our knowledge, this is the first demonstration of a 100 μJ-level, tens of kilowatts-peak-power-level single frequency linearly polarized 775 nm laser based on the frequency doubling of the fiber lasers.
1018nm short wavelength Yb3+-doped fiber laser can be widely used for tandem-pumped fiber laser system in 1 μm regime because of its high brightness and low quantum defect (QD). In order to achieve 1018nm short wavelength Yb3+-doped fiber laser with high output power, a steady-state rate equations considering the amplified spontaneous emission (ASE) and Stimulated Raman Scattering (SRS) has been established. We theoretically analyzed the ASE and SRS effects in 1018nm short wavelength Yb3+-doped fiber laser and the simulation results show that the ASE is the main restriction rather than SRS for high power 1018nm short wavelength Yb3+-doped fiber laser, besides the high temperature of fiber is also the restriction for high output power. We use numerical solution of steady-state rate equations to discuss how to suppress ASE in 1018nm short wavelength fiber laser and how to achieve high power 1018nm short-wavelength fiber laser.
Single-frequency fiber laser operating at 1950 nm has been demonstrated in an all-fiber distributed Bragg reflection (DBR) laser cavity by using a 1.9-cm commercial available Thulium-doped silica fiber, for the first time. The laser was pumped by a 793-nm single-mode diode laser and had a threshold pump power of 75 mW. The maximum output power of the single longitudinal mode laser was 18 mW and the slope efficiency with respect to the launched pump power was 11%. Moreover, the linewidth and relative intensity noise (RIN) at different pump power has been measured and analyzed. The successful demonstration with the Thulium-doped silica fiber used here is considered to further promote the commercialization of single frequency fiber laser at 2 μm.
Two simple and low-cost methods for achieving selective filling of air-core photonic bandgap fibers (PBGFs) are
proposed and demonstrated. In the first method, liquid paraffin was filled into a PBGF by capillary force. By a two-step
filling-cleaving process, all cladding air-holes are finally blocked but the air-core remains open. In the second method,
lateral erosion method by hydrofluoric acid was first used to make the cladding air-holes laterally open. Then, the
laterally filled liquid paraffin made all cladding air-holes blocked and left only air-core open. With these two methods,
the central hollow-core of the PBGF can be selectively filled, which allows for the fabrication of novel hybrid
functional-material-silica PBGF for various applications.
We propose a novel design of dual-concentric-core all-solid photonic bandgap fiber (DCC-AS-PBGF). It is designed by
introducing a ring of bigger high-index rods, a new defect, in the cladding of a conventional all-solid PBGF. Using plane
wave expansion method (PWEM) and full-vector finite-element method (FEM), we study the effect of introducing such
a ring of bigger high-index rods. The numerical results show that large dispersion is gained around the wavelength where
the modes in the new defect couple with the modes in the core. More importantly, the confinement loss of the LP01
modes around the wavelengths, where large dispersion is induced, could be decreased by increasing the rings of high-index
rods for the fact that these waveband are within the bandgap.