494.5 nm generation by sum-frequency mixing of diode pumped neodymium lasers

We report a coherent radiation at 494.5 nm by intra-cavity sum-frequency generation of 912 nm Nd:GdVO₄ laser and 1080 nm Nd:CaYAlO₄ laser. Blue laser is obtained by using a doubly folded cavity, type-II critical phase matching KTP (KTiOPO₄) crystal sum-frequency mixing. With total pump power of 33 W (13.8 W pump power for 1080 nm Nd:CaYAlO₄ laser and 19.2 W pump power for 912 nm Nd:GdVO₄ laser), TEM₀₀ mode blue laser at 494.5 nm of 1.6 W is obtained. The power stability in 30 min is better than 3.5%.     

Diode-pumped Nd:YVO4-Nd:CNGG crystals blue laser at 462 nm by intracavity sum-frequency-mixing

We report a laser architecture to obtain continuous-wave (cw) blue radiation at 462 nm. A 808 nm diode-pumped the Nd:YVO₄ crystal emitting at 914 nm. A part of the pump power was then absorbed by the Nd:YVO₄ crystal. The remaining was used to pump the Nd:CNGG crystal emitting at 935 nm. Intracavity sum-frequency mixing at 914 and 935 nm was then realized in a LiB₃O₅ (LBO) crystal to reach the blue radiation. We obtained a continuous-wave output power of 892 mW at 462 nm with a pump laser diode emitting 18.4 W at 808 nm.     

Experiments of all-optical switching due to cross-phase modulation in fiber grating coupler by lock-in amp. detection scheme

We report results of experiments examining cross-phase modulation effect on fiber grating coupler (FGC). All-optical switching are observed in both cases of high pump pulses emitted from high-power Nd:YAG laser and mode-locked EDF laser. Based on coherent detection using a lock-in amplifier, the red-shift of the Bragg wavelength for a FGC was estimated to be 0.04-0.06 nm/1.5-1.7 kW peak power of EDF pump light at 1.55 μm. To avoid mixture of pump pulse and signal light at 1.55 μm, we have also performed the experiment using high power Nd:YAG laser as a pump power. For a Nd:YAG laser, the red-shift of Bragg wavelength is estimated to be 0.06 nm at maximum pump power of 2.1 kW. A simple model for the proposed detection scheme is given and the resultant red-shift is analyzed numerically.     

Dual-wavelength high-power Yb-doped double-clad fiber laser based on a few-mode fiber Bragg grating

We report a high-power dual-wavelength Yb-doped double-clad fiber laser based on a few-mode fiber Bragg grating (FMFBG). The FMFBG was fabricated by using a piece of fiber in a length of fiber with a cutoff wavelength of 1225 nm, which supported two modes at 1060 nm. The laser was pumped by a fiber pigtailed laser diode working at 915 nm. Single-wavelength, dual-wavelength and triple-wavelength laser oscillations were observed when the fiber laser operated under different low pump powers. However, stable dual-wavelength operation was achieved at higher pump power of 3.9 W and remained unchanged until the output power reached 5.67 W under the maximum available pump power of 10.7 W. The laser wavelengths were centered at 1059.12 and 1060.80 nm with a full-width at half-maximum of 37 and 43 pm, respectively. The signal-to-noise-ratio was greater than 50 dB and the beam quality factor (M²) was about 1.9.     

Diode-pumped Nd:LuVO4-Nd:YLiF4 crystals blue laser at 489 nm by intracavity sum-frequency-mixing

We present a laser architecture to obtain continuous-wave blue radiation at 489 nm. An 809 nm diode-pumped the Nd:LuVO₄ crystal emitting at 916 nm. A part of the pump power was then absorbed by the Nd:LuVO₄ crystal. The remaining was used to pump the Nd:YLiF₄ (Nd:YLF) crystal emitting at 1047 nm. Intracavity sum-frequency mixing at 916 and 1047 nm was then realized in a LiB₃O₅ (LBO) crystal to reach the blue radiation. We obtained a continuous-wave output power of 425 mW at 489 nm with a pump laser diode emitting 18.4 W at 809 nm.     

Optimization of erbium-doped fiber MOPA laser

An erbium-doped fiber laser (EDFL) constructed in a master oscillator and power amplifier (MOPA) configuration is analyzed. The pump powers for the fiber cavity laser and the booster amplifier stages are managed properly to achieve maximal pump conversion efficiency. Our design achieves a pump conversion efficiency of 91.4%, corresponding to a quantum efficiency of 96.6%, for a 1565.8 nm MOPA laser pumped by a total power of 300 mW at 1480 nm. The optimized MOPA laser shows a 25% enhancement in the pump conversion efficiency, compared to a non-MOPA fiber laser. A side lobe suppression ratio of 48 dB for the optimized MOPA laser is observed.     

Theoretical and experimental investigations of a diode-pumped high-power continuous-wave 912 nm Nd:GdVO4 laser operation at room temperature

Based on the rate equation of Nd³⁺-doped quasi-three-level lasers, a theoretical model of diode-end-pumped continuous-wave 912 nm Nd:GdVO₄ laser is presented. Lasing threshold and slope efficiency considering reabsorption effect are calculated and analyzed. It is found that the output performance of 912 nm laser operating at room temperature is influenced remarkably by the reabsorption loss and spatial distribution of the pump beam and laser beam. In experiments, the output power and average slope efficiency of 912 nm laser were investigated under different conditions. After optimization at the parameters of laser medium, working temperature and spatial distribution of the pump beam, up to 16.2 W continuous-wave 912 nm laser output was obtained at incident pump power of 67.0 W, with an average slope efficiency of 41.7%, to the best of our knowledge, this is the highest output power of diode-pumped 912 nm Nd:GdVO₄ laser by far.     

Wavelength tunability of L-band fiber ring lasers using mechanically induced long-period fiber gratings

We report on oscillation wavelength control in erbium-doped fiber ring lasers by adjusting the period of a mechanically induced long-period fiber grating (LPFG) inserted into the fiber ring resonator. Pump light is provided by a 974 nm laser diode (LD), the emission of which is coupled into the fiber ring resonator through a wavelength-division multiplexing coupler. Laser oscillation occurs with a threshold pump LD current of 40 mA, corresponding to a threshold pump power of 5 mW. When a periodic pressure of 0.81 N/mm is applied to form the LPFG, the fiber ring laser exhibits the tunable range of 40.9 nm, i.e., from 1563.1 to 1604 nm, by changing the grating period.     

41 mW high average power picosecond 177.3 nm laser by second-harmonic generation in KBBF

We report on the generation of high average power, high repetition rate, and picosecond (ps) deep-ultraviolet (DUV) 177.3 nm laser. The DUV laser is produced by second-harmonic generation of a frequency-tripled mode-locked Nd: YVO₄ laser (<15 ps, 80 MHz) with KBBF nonlinear crystal. The influence of different fundamental beam diameters on DUV output power and KBBF-SHG conversion efficiency are investigated. Under the 355 nm pump power of 7.5 W with beam diameter of 145 μm, 41 mW DUV output at 177.3 nm is obtained. To our knowledge, this is the highest average power for the 177.3 nm laser. Our results provide a power scaling by three times with respect to previous best works.     

Efficient 1047 nm CW laser emission of Nd:YLF under direct pumping into the emitting level

We demonstrate a 1047 nm Nd:LiYF₄ (Nd:YLF) laser by directly pumping into the upper lasing level with a tunable Ti:Sapphire laser. The results obtained for direct upper laser level pumping at 863, 872 and 880 nm of Nd:YLF were compared with traditional 806 nm pump band excitation. Highly efficient 1047 nm continuous-wave (CW) laser emission under direct pumping at 880 nm in an 8 mm thick, 1.0 at.% Nd:YLF crystal is obtained. The slope efficiency is improved from 55.6% for traditional pumping at 806 nm to 76.3% for direct pumping at 880 nm.     

Three-level operation of a diode-bar-pumped Yb:S-FAP laser

We present an all solid-state Yb:S-FAP laser system running on the three-level laser transition at 985 nm. The pump source was a high fill-factor laser diode bar, with the output reformatted using a two-mirror beamshaping system to produce a rectangular pump beam that focused to a square spot. A nearly on-axis multipassing system was used to obtain four pump passes through a 1.6 mm Yb:S-FAP laser crystal. Gain-switched three-level laser output was achieved with an efficiency of 4.3% with respect to incident pump power. Electro-optic Q-switching produced 0.12 mJ pulses for a pump pulse energy of 11 mJ. Intra-cavity second-harmonic generation yielded a maximum pulse energy at 492.5 nm of 12 μJ.     

A novel double-Brillouin-frequency spaced multi-wavelength Brillouin erbium-doped fiber laser based on non-linear amplified fiber loop mirror

In the paper, a ring double-Brillouin-frequency spaced multi-wavelength Brillouin erbium-doped fiber laser based on non-linear amplified fiber loop mirror filter is demonstrated, in which the non-linear amplified fiber loop mirror (AFLMF) is used as a filter. At the 980 nm pump power of 10.29 dBm, the tunable laser source center wavelength of 1563 nm and power of −3 dBm, up to 12 even output channels with 0.16 nm spacing are achieved. At the same time, we study the influence of 980 nm pump power, the polarization controller and the tunable laser source center wavelength on the number of Stokes light wave.     

Tm:Ho co-doped single mode optical fibre laser pumped by a 1600 nm Er fibre laser

An all-fibre Tm:Ho laser system is reported, using a 1600 nm Er fibre pump laser and 0.3 m length of the fibre through a two-stage optimization of both the pump source and laser configuration to achieve a low threshold operation. As a result a low threshold power of 33 mW and a slope efficiency of 0.6% have been achieved, in laser operation at a wavelength of 1870 nm and a cross-comparison with 785 nm laser diode pumping has been made.     

High efficiency Tm fiber laser of seed amplification

We use all-fiber single-mode lasers as seed source, amplifiers and pump laser coupling amplifier has been experimentally investigated, respectively. The maximum output power is 10.4 W, with the slope efficiency of 54.4% when the seed laser power is 1 W, and the slope efficiency is 48.7% when the seed laser power is 2 W. The slope efficiency of this scheme is higher than that of the all-fiber amplifier. This can be explained by the loss of pump power at the splice dots. The wavelength of the fiber amplifier is 1947.6 nm, the same as the seed laser's, with a linewidth of 2 nm. We estimate the beam quality to be M² = 2.39, clearly indicating nearly diffraction-limited beam propagation.     

Highly efficient Nd:GdVO4/BiBO laser at 456 nm under direct 880 nm diode laser pumping

The continuous-wave high-efficiency laser emission of Nd:GdVO₄ at the second-harmonic of 456 nm obtained by intracavity frequency doubling with an BiB₃O₆(BiBO) nonlinear crystal is investigated under pumping by diode laser at 880 nm into emitting level ⁴F_3/2. About 3.8 W at 456 nm with M² = 1.4 was obtained from a 5 mm-thick 0.4 at.% Nd:GdVO₄ laser medium and a 12 mm-long BiBO nonlinear crystal in a Z-type cavity for 13.9 W absorbed pump power. An optical-to-optical efficiency with respect to the absorbed pump power was 0.274. Comparative results obtained for the pump with diode laser at 808 nm, into the highly-absorbing ⁴F_5/2 level, are given in order to prove the advantages of the 880 nm wavelength pumping.     

Simple tunable multiwavelength Brillouin/Erbium fiber laser utilizing short-length photonic crystal fiber

We have demonstrated a simple ring cavity tunable multiwavelength Brillouin/Erbium fiber laser (MWBEFL), in which 70 m highly nonlinear photonic crystal fiber (HNL-PCF) is used as the Brillouin gain medium. The fiber laser utilizes recycling mechanism to enhance stimulated Brillouin scattering (SBS). The configuration that consists of only 3 optical components is easy to be integrated and improves the practicality. At the maximum 1480 nm pump power of 110 mW and the Brillouin pump power of 3 dBm, 10 stable output channels with more than 10 dB optical signal to noise ratio (OSNR) and 0.078 nm channel spacing could achieve 10 nm tuning ranges.     

Diode-pumped passively Q-switched Nd:LuVO4 laser at 916 nm

We demonstrate a passively Q-switched Nd:LuVO₄ laser at 916 nm by using a Nd, Cr:YAG crystal as the saturable absorber. As we know, it is the first time to realize the laser with a simple linear resonator. When the incident pump power increased from 14.6 W to 23.7 W, the pulse width of the Q-switched laser decreased from 24 ns to 21 ns. The pulse width was insensitive to the incident pump power in the experiment. The average output power of 288 mW with repetition rate of 39 kHz was obtained at an incident pump power of 22.5 W, with the optical-to-optical efficiency and slope efficiency 1.3% and 3.6%, respectively.     

Gain-saturated Ni-like antimony laser at 11.4 nm in grazing-incidence pumping geometry

We report on gain-saturated operation of the 4d → 4p, J = 0-1, 11.4 nm soft-X-ray laser line in Ni-like antimony (Sb) at a pump energy of only 2.5 J. The driving laser used was a 1054 nm Nd:glass CPA laser system with a pulse duration of 7 ps (FWHM). The pump beam was focused with a tilted on-axis parabolic mirror in a grazing-incidence (GRIP) pumping configuration at an incidence angle of 45°. A fraction of 2.8% of the pump energy (∼70 mJ) was used for the prepulse, which was propagated along the same beam line as the main pulse and arrived at the target 4.4 ns before the main pulse.     

Low threshold, actively Q-switched Nd:YVO4 self-Raman laser and frequency doubled 588 nm yellow laser

We reported an actively Q-switched, intracavity Nd³⁺:YVO₄ self-Raman laser at 1176 nm with low threshold and high efficiency. From the extracavity frequency doubling by use of LBO nonlinear crystal, over 3.5 mW, 588 nm yellow laser is achieved. The maximum Raman laser output at is 182 mW with 1.8 W incident pump power. The threshold is only 370 mW at a pulse repetition frequency of 5 kHz. The optical conversion efficiency from incident to the Raman laser is 10%, and 1.9% from Raman laser to the yellow.     

800 mW/1484 nm highly efficient two-cascaded phosphosilicate Raman fiber laser pumped by Nd:YVO4 solid-state laser

Using 1064 nm CW Nd:YVO₄ solid-state laser as a pump, 1-km phosphosilicate fiber and cascaded cavities with two pairs of fiber Bragg grating mirrors for 1239 and 1484 nm, we obtained a CW 800 mW/1484 nm Raman fiber laser (RFL) for an actual incident pump power of about 2 W (Nd:YVO₄ power of 6.90 W). The conversion efficiency is as high as 40%. To the best of our knowledge, this is the highest conversion efficiency of RFL pumped by solid-state laser. The output power instability at 1484 nm in half an hour is less than 3%. In addition, the numerical simulations are also performed. Good agreement between the results of numerical simulation and the results of the experiment has been demonstrated.