Q-switched Dual-wavelength Laser Research Articles

Generation of dual-wavelength Q-switched laser pulses by employing Mo2Ti2AlC3 MAX phase film

In this paper, we experimentally generate dual-wavelength laser pulses from a Q-switched erbium-doped fiber laser (QS-EDFL) by utilizing molybdenum titanium aluminum carbide (Mo2Ti2AlC3) MAX Phase film. The Mo2Ti2AlC3-SA film, which belongs to the MAX phase compound, is prepared using the mechanical exfoliation. The optical and physical properties of Mo2Ti2AlC3-SA are investigated. The fabricated film has a linear absorption of 8 dB and modulation depth of 17 % at 1.55 mm region. A steady dual-wavelength Q-switched laser pulses are achieved with 1531.6 nm and 1557 nm peaks and a free spectral range (FSR) of 25.4 nm. By increasing the input pump power from 131.87 mW to 167 mW, the repetition rate of generated pulses is varied over 104 kHz to 126 kHz. At the highest input power (167 mW), the energy and output power of the obtained pulses are 87.30 nJ and 11 mW, respectively. The results reveal that the exfoliated Mo2Ti2AlC3-SA can be operated inside EDFL to produce stable pulses with dual wavelengths.

Passively Q-switched Dual-wavelength Laser Based on Nd∶GdVO4 Crystal

Passively Q-switched Dual-wavelength Laser Based on Nd∶GdVO4 Crystal

Passively Q-Switched Dual-Wavelength Laser Operation With Coaxially End-Pumped Composite Laser Materials

A passively Q-switched dual-wavelength laser with tunable power ratio and pulse interval is demonstrated based on the coaxial diode end-pumping configuration by varying the pump wavelength. A theoretical model was built by a set of time-domain rate equations illustrating the dynamic process of both the pulse generation of two wavelengths from a shared pump source and a saturable absorber. The simulation showed that both the power ratio and the time interval between the pulses at two resonant wavelengths in the Q-switched mode could be tuned by balancing the gains in two laser crystals by varying the pump wavelength, realized by controlling the working temperature of the pump laser diode. The experiment was performed with Nd:YAG/Nd:YAP composite laser crystals and a Cr4+:YAG slice working as the saturable absorber for pulse generation. The continuous-wave and Q-switched total output power reached 5.62 W and 2.12 W, corresponding to overall optical-optical conversion efficiencies of 37.5% and 14.1%, respectively. The manipulation of power ratio and pulse interval between 1064 nm and 1080 nm agreed well with the simulation results.

Tunable dual-wavelength saturable absorber based on dual defective photonic crystal by MoS2 monolayer

Dual-wavelength Q-switched lasers have currently received extensive attention due to their wide applications in nonlinear optoelectronic devices. Their main mechanism can be based on the integration of laser with devices such as dual defective photonic crystals (DPCs). Nonetheless, DPCs with a high modulation depth is still demanding in this field. Toward this goal, in this paper, we have designed a dual DPC with MoS2 monolayers as defects in this structure. Defect modes helped adjust the wavelength by the distance between the two defects, and finally, a tunable wavelength was created by changing the intensity, incident angle, and polarization. Using the dual DPC, modulation depth was increased to 97% and 85% in the dual defect modes and a wide range of light intensities was achieved with over 80% of absorption, which helps accomplish a tunable dual Q-switching operation.

Simultaneous dual-wavelength Q-switched fiber laser utilizing tungsten sulfide as saturable absorber

Dual-wavelength Q-switched Erbium-doped fiber laser (EDFL) was shown by using tungsten disulfide (WS2), which was deposited onto a micro-sphere resonator (MSR) as a saturable absorber (SA). WS2 functions to modulate the cavity loss for Q-switching while the dual-wavelength operation was realized due to MSR, which allows only two wavelengths to oscillate in the resonator. MSR with the sphere diameter of 200 μm was fabricated at the tip of a standard single mode-fiber by employing a fiber fusion splicer machine. The SA was obtained by repeatedly dropping and drying of WS2 solution onto the MSR structure to form an active thin layer. The SA was incorporated into an EDFL cavity to realize a dual-wavelength Q-switched laser operating at 1554.0 nm and 1560.7 nm. The repetition rate of the pulse train is tunable from 72.4 kHz to 85.1 kHz as the pump power is increased from 104.6 mW to 145.8 mW. At 145.8 mW pump, the minimum pulse width and maximum pulse energy were obtained at 3.47 µs and 131.4 nJ, respectively. The dual-wavelength Q-switched laser was stable and thus it is suitable for use in airborne Lidar, environmental sensing, and terahertz applications.

Dual-wavelength Q-switched laser based on a lens-shaped Nd : YAG active element and a Cr4+: YAG passive Q-switch

Dual-wavelength Q-switched lasing at wavelengths of 1047 and 1053 nm is achieved in a longitudinally diode-pumped laser with a lens-shaped Nd:YLF active element and a Cr4+ : YAG passive Q-switch. Dual-wavelength lasing is achieved as a result of transverse mode locking due to the choice of a cavity length corresponding to the close-to-semiconfocal configuration, which provides identical gains for the two laser wavelengths.

Characterization of SnSe2 saturable absorber by THz-TDS and used in dual-wavelength passively Q-switched laser

We firstly used THz-TDS to characterize the 2D-material (SnSe2) saturable absorber (SA) with nondestructive and high resolution. In addition, the application of the SnSe2 SA for dual-wavelength Q-switched laser is demonstrated. The highest dual-wavelength output power of 438 mW with the optical to optical efficiency of 9.7%. The minimum pulse width is 237 ns at the repetition rate of 72 kHz can be obtained. This results indicate that the THz transmission spectrum could be used to characterize the SAs and the tin diselenide SA also shows good features used in dual-wavelength solid state lasers.

Rhenium disulfide-based passively Q-switched dual-wavelength laser at 0.95 μm and 1.06 μm in Nd:YAG

We demonstrate a passively Q-switched dual-wavelength (0.95 μm, 1.06 μm) neodymium-doped laser based on a few-layer rhenium disulfide (ReS2) saturable absorber (SA). By a liquid exfoliation method, few-layer ReS2 was prepared, and then its nonlinear optical response was examined by an open aperture Z-scan method. By using a ReS2 SA, a 0.95, 1.06 μm dual-wavelength pulsed solid state laser with a mode waist controllable linear multi-mirror cavity has been reported for the first time. The ReS2 SA Q-switched dual-wavelength oscillation threshold was recorded to be 1.35 W. At the absorbed pump power of 3.07 W, a maximum average output power of 81 mW was obtained, corresponding to the shortest pulse width of 834 ns and a repetition frequency of 165 kHz. This is, to our knowledge, the first assessment of saturable absorption and dual-wavelength Q-switching ability adjacent to the bandgap of ReS2. The result indicates that few-layered ReS2 SAs are good candidates for 0.95, 1.06 μm simultaneous pulsed laser oscillating systems.

Q-Switched Dual-Wavelength Laser at 1116 and 1123 nm Using WS2Saturable Absorber

Longitudinally diode-pumped continuous-wave dual-wavelength Nd:YAG laser at 1116 and 1123 nm is achieved with maximum output power of 8.18 W and slope efficiency of 42.3%. Using WS 2 as saturable absorber, passive Q-switching of the dual-wavelength laser is also achieved with a maximum average output power of 0.41 W, the shortest pulse width of about 0.64 μs at pulse repetition rate of 100.9 kHz. The present Q-switched laser operation leads to maximum pulse energy of 4.06 μJ and pulse peak power of 6.35 W. A 2-D material WS 2 has been experimentally confirmed to be very promising as Q switcher at 1.1 μm, for the first time to our knowledge.

Dual-wavelength, passively Q-switched thulium-doped fiber laser with N-doped graphene saturable absorber

Demonstrations of dual-wavelength Q-switched fiber lasers in the wavelength regions of 1.0μm and 1.55μm have been widely reported but not in the longer wavelength of 2.0μm region. In this paper, a dual-wavelength Q-switched thulium-doped fiber laser is proposed and demonstrated using an N-doped graphene film as the saturable absorber, while the dual-wavelength mechanism is achieved with the use of a tunable Mach-Zehnder filter. The dual-wavelength Q-switched laser produced consistent outputs at 1922.0nm and 1961.0nm with a wavelength spacing of 39.0nm. The repetition rate of the pulses obtained covers a range from 17.68kHz to 35.21kHz corresponding to an increasing pump power of 112.55mW until 147.78mW. The narrowest pulse width obtained is 4.4μs and a pulse energy as high as 25.56nJ is generated. To the best of our knowledge, this is the first demonstration of a dual‐wavelength Q-switched thulium-doped fiber laser operating in the 2.0μm wavelength region using a fiber ring cavity design.

New continuous-wave and Q-switched eye-safe Nd:YAG lasers at 1.4 μm spectral region

We report new results concerning 1.4 μm eye-safe laser sources based on a conventional Nd:YAG crystal. In free-running laser mode, we obtain the highest output power of 4.64 W at 1413 nm with slope efficiency of about 23.1%. With the aid of an etalon, we achieve a simultaneous dual-wavelength laser at 1413 and 1443 nm with maximum output power of 3.18 W and slope efficiency of about 16.7%. In addition, a single wavelength laser at 1431 nm is also yielded with maximum output power of 1.96 W and slope efficiency of about 11.8%. The dual-wavelength laser and single-wavelength laser (1431 nm) are believed to be the first demonstrations from diode-pumped Nd:YAG crystal. Using a single-wall carbon nanotube as the saturable absorber, we achieve dual-wavelength Q-switched laser operation at 1413 and 1443 nm with the narrowest pulse width of about 0.49 μs, for the first time to our knowledge.

Dual-wavelength passively Q-switched Erbium-doped fiber laser with MWCNTs slurry as saturable absorber

In this work, a compact, stable dual-wavelength Q-switched laser with a multi-walled carbon nanotubes (MWCNTs) slurry as saturable absorber (SA) which is independent of any host polymer has been demonstrated. The MWCNTs slurry is fabricated and the peak shift is investigated using Raman spectroscopy.The passively Q-switched erbium-doped fiber laser (EDFL) oscillated simultaneously at 1532.32 nm and 1556.97 nm with 24.67 nm peak separation, at threshold and maximum input power of 26mW and 74mW respectively.By increasing the input pump power from 36 mW to 74 mW, the pulse train repetition rate increases from 25 kHz to 78 kHz, while the pulse width is reduced from 17.84 us to 5.24 ?s. The generated pulse produced maximum pulse energy and maximum peak power of 11.97 nJ and 2.05 mW, respectively at maximum input pump power. The recorded signal to noise ratio is about 62 dB and shows that the proposed MWCNTs slurry based SAis able to generate dual wavelength Q-switched pulse laser with high stability pulse. Full Text: PDF ReferencesL.Liu, Z. Zheng, X. Zhao,S. Sun, Y. Bian, Y. Su, J. Liu, and J. Zhu, "Dual-wavelength passively Q-switched Erbium doped fiber laser based on an SWNT saturable absorber", Optics Communications 294, 267 (2013). CrossRef Z. Luo, M. Zhou, J. Weng, G. Huang, H. Xu, C. Ye, and Z. Cai, "Graphene-based passively Q-switched dual-wavelength erbium-doped fiber laser", Optics Letters 35, 3709 (2010). CrossRef F. Lou, R. Zhao, J. He, Z. Jia, X. Su, Z. Wang, J. Hou, and B. Zhang, "Nanosecond-pulsed, dual-wavelength, passively Q-switched ytterbium-doped bulk laser based on few-layer MoS2 saturable absorber", Photon. Res. 3, A25 (2015). CrossRef F. A. A. Rashid et al., "Using a black phosphorus saturable absorber to generate dual wavelengths in a Q-switched ytterbium-doped fiber laser", Laser Phys. Lett. 13, 1 (2016). CrossRef J. Sotor, G. Sobon, I. Pasternak, K. Krzempek, G. Dudzik, A. Krajewska, W. Strupinski, and K. M. Abramski, "Dual-wavelength fiber mode-locked laser based on graphene saturable absorber", Proc. of SPIE 8961, 89612A (2014). CrossRef S. Alwarappan, and A. Kumar, Graphene-Based Nanomaterials (Boca Rota, CRC Press 2014).N. Taib, N. Bidin, H. Haris, N. N. Adnan, M. Ahmad, and S. W. Harun, "Multi-walled carbon nanotubes saturable absorber in Q-switching flashlamp pumped Nd:YAG laser", Optics & Laser Technology 79, 193 (2016). CrossRef M. Ahmad, A. Latiff, Z. Zakaria, and S. Harun, "Q-Switched Ultrafast TDFL Using MWCNTs-SA at 2 ?m Region", International Journal of Computer and Communication Engneering 3, 446 (2014). CrossRef H. Ahmad, K. Z. Hamdan, F. D. Muhammad, S. W. Harun, and M. Z. Zulkifli, "Switchable dual-wavelength CNT-based Q-switched using arrayed waveguide gratings (AWG)", Applied Physics B 118, 269 (2015). CrossRef J. M. Dudley and J. R. Taylor, Supercontinuum Generation in Optical Fibres (New York, Cambridge University Press 2010). CrossRef H. Ahmad, M. A. M. Salim, M. R. K. Soltanian, S. R. Azzuhri, and S. W. Harun, "Passively dual-wavelength Q-switched ytterbium doped fiber laser using Selenium Bismuth as saturable absorber", Journal of Modern Optics 62, 1550 (2015). CrossRef H. Chu et al., "Dual-Wavelength Passively Q-Switched Nd,Mg:LiTaO3 Laser With a Monolayer Graphene as Saturable Absorber", IEEE Journal of Selected Topics in Quantum Electronics 21, 1600705 (2015). CrossRef Z. T. Wang, Y. Chen, C. J. Zhao, H. Zhang, and S. C. Wen, "Switchable Dual-Wavelength Synchronously Q-Switched Erbium-Doped Fiber Laser Based on Graphene Saturable Absorber", IEEE Photonics Journal 4, 869 (2012). CrossRef J. H. Liu et al., "Passively Q-switched dual-wavelength Yb:LSO laser based on tungsten disulphide saturable absorber", Chin. Phys. B 25, 034207 (2016). CrossRef Z. C. Tiu et al, "Multi-wavelength Q-switched Erbium-doped fiber laser with photonic crystal fiber and multi-walled carbon nanotubes", Journal of Modern Optics 61, 1133 (2014). CrossRef

Dual-wavelength Q-switched Er:SrF2 laser with a black phosphorus absorber in the mid-infrared region.

An efficient Er:SrF2 crystal, lightly Er-doped to a concentration of 4at.%, was successfully grown by the traditional Bridgman method and displayed excellent spectral properties. A diode-end-pumped passively Q-switched dual-wavelength laser, operating at 2.79 μm wavelength, was demonstrated with this crystal by using black phosphorus as the saturable absorber (BP-SA). In the compact passively Q-switched Er:SrF2 laser, the maximum average output power of 180 mW was achieved at an absorbed pump power of 2.47 W, with a pulse duration of 702 ns and a repetition rate of 77.03 kHz. To the best of our knowledge, this is the first reported application of BP-SA to dual-wavelength pulse laser operation in the mid-infrared region.

Dual-wavelength eye-safe Nd:GYSGG/YVO4 intracavity Raman laser under in-band pumping

An acousto-optic (AO) Q-switched dual-wavelength laser operating at 1.5µm eye-safe region is demonstrated via stimulated Raman scatting of a-cut YVO4-Nd:YVO4 crystal within an end-pumped dual-wavelength Nd:GYSGG laser cavity. The in-band pumping absorption peak and coefficient of the dual-wavelength laser crystal Nd:GYSGG are measured in order to carry out efficient pumping, thus overcoming the drawbacks of short thermal focal length of the crystal and scale up the eye-safe output. Under 23.2W absorbed pump power, 2.11W of simultaneous dual-wavelength outputs at 1497 and 1516nm are obtained with a pulse repetition rate of 23kHz and a corresponding conversion efficiency of 9.1%.

Actively Q-switched dual-wavelength laser with double-cladding Er/Yb-doped fiber using a Hi-Bi Sagnac interferometer

An actively Q-switched double-wavelength Er/Yb fiber laser is experimentally demonstrated. The linear cavity is formed by a pair of fiber Bragg gratings on one side and a Sagnac interferometer (SI) with high birefringence fiber in the loop on the opposite side. A 3 m of double-cladding Er/Yb-doped fiber used as a gain medium is pumped by a 978 nm laser diode. The SI is used to adjust the internal cavity losses for simultaneous dual-wavelength laser generation. The adjustment is performed by temperature variations of the high birefringence fiber in the SI loop. The maximum average output power for the Q-switched laser operation in dual-wavelength mode was around 68 mW with a repetition rate of 40 kHz for 2 W of pump power. The minimum pulse duration was around 280 ns. The maximum pulse energy was 1.75 µJ.

Switchable dual-wavelength CNT-based Q-switched using arrayed waveguide gratings (AWG)

In this paper, a dual-wavelength synchronously pulsed fiber laser Q-switched by carbon nanotube-based saturable absorber with switchable wavelength spacing enabled using arrayed waveguide grating (AWG) is proposed and demonstrated. By just switching the channels of the AWG, discrete tuning in wavelength spacing of the dual-wavelength Q-switched laser operation can be attained over several nanometers, ranging from 1.6 to 4.0 nm in a stable dual-wavelength regime without employing any modulation technique or intracavity spectral filters. Our experimental results show that the fiber laser can generate Q-switched microsecond pulses with a wide repetition rate range, starting from 12.0 kHz to a maximum value of 54.9 kHz. This proposed system is also reasonably simple to realize at low cost.

Energy extraction in dual-wavelength Q-switched laser with a common upper laser level

The effect of lower-laser-level lifetimes on Q-switched pulse generation in a dual-wavelength solid-state laser with a common upper laser level was numerically and experimentally investigated. A rate-equation model that accounts for finite lower-laser-level lifetimes was developed, and for a Nd:YAG laser operating at 1064 and 1319 nm, numerical simulations of dual-wavelength pulse generation were performed with and without the effects of lower-laser-level lifetimes. In the laser experiments, characteristics of the dual-wavelength Q-switched pulses agree reasonably well with theoretical predictions. As a result, we found that both the total energy of the two Q-switched pulses and the ratio of 1064–1319-nm pulse energies were strongly affected by the lower-laser-level lifetimes when the Q-switched pulse width was comparable or shorter than the lower-laser-level lifetime.

Efficient Continuous-Wave 1053-nm Nd:GYSGG Laser With Passively Q-Switched Dual-Wavelength Operation for Terahertz Generation

Research on an efficient continuous-wave Nd:GYSGG laser at 1053 nm with excellent stability is demonstrated. The maximum output power is 4.17 W, corresponding to the conversion efficiency of 33.9% and the slope efficiency of 42.92%. Using a Cr:YAG absorber, pulsed dual-wavelength operation at 1053 and 1058.4 nm is obtained, of which the maximum single pulse energy and peak power are 172.1 μJ and 26.1 kW, respectively, when the pulse width is 6.6 ns and the repetition rate is 4.3 kHz. A polarization property is observed, owing to the anisotropy of Cr:YAG. This stably Q-switched dual-wavelength laser is a good pump source for the generation of a terahertz wave at 1.53 THz.

Simultaneous dual-wavelength operation of Nd:YVO_4 self-Raman laser at 1524 nm and undoped GdVO_4 Raman laser at 1522 nm

A diode-pumped, actively Q-switched dual-wavelength laser employing Nd:YVO(4) self-Raman emission at 1524 nm and undoped GdVO(4) Raman emission at 1522 nm is demonstrated. With a pump power of 21.5 W and pulse repetition frequency of 20 kHz, a maximum dual-wavelength output power of 1.62 W was obtained, comprising a 0.54 W, 1522 nm Raman component and 1.08 W, 1524 nm self-Raman component. The corresponding dual-wavelength Raman pulse width was 5.6 ns. The experimental results indicate that this laser, with quite small wavelength separation, was effective by virtue of simultaneous self-Raman and Raman shifts.

Passively Q-switched Nd:Sc_02Y_08SiO_5 dual-wavelength laser with the orthogonally polarized output

We have demonstrated a laser-diode pumped continuous-wave (CW) and passively Q-switched laser with a Nd:Sc(0.2)Y(0.8)SiO(5) (Nd:SYSO) crystal for the first time. In the CW operation, the laser was found to oscillate in tri-wavelength regime at 1074.8 nm, 1076.6 nm and 1078.2 nm, respectively. The maximum CW output power of 1.96 W was obtained, giving an optical-to-optical conversion efficiency of 35% and a slope efficiency of 39%. Using either Cr(4+):YAG or V(3+):YAG crystal as saturable absorber, stable passively Q-switched laser was obtained at dual-wavelength of 1074.8 nm and 1078.2 nm with orthogonal-polarization. The maximum average output power, pulse repetition rate, and shortest pulse width were 1.03 W, 50 kHz, and 24 ns, respectively. The passively Q-switched dual-wavelength laser could be potentially used as a source for generation of terahertz radiation.