Largest Pulse Energy Research Articles

Self-mode-locked 2 μm Tm3+-doped double-clad fiber laser with a simple linear cavity

We demonstrate the self-mode-locking operation of a thulium (Tm)-doped fiber laser (TDFL) with a simple linear cavity. Since the laser cavity does not include any specific mode-locker, we experimentally investigate and analyze the self-mode-locking mechanism. The mode-locking operation is attributed to the combination of the self-phase modulation effect and the weak saturable absorption of the high-concentration Tm-doped fiber. The mode-locked TDFL operates at a central wavelength of 1985.5nm with the 3dB spectral linewidth of 0.18nm. The self-mode-locking generates a large pulse energy of 32.7nJ with a pulsed repetition rate of 2.05MHz and is stable with a radio-frequency signal-to-noise ratio of more than 54dB. To the best of our knowledge, it is the first demonstration of a 2μm Tm-doped fiber laser mode-locked by such technique.

Tunable stoichiometry of BCxNy thin films through multitarget pulsed laser deposition monitored viain situellipsometry

The supercontinuum (SC) generated by pumping in anomalous dispersion is sensitive to the input pulse fluctuations and pump laser’s shot noises and does not possess a single-pulse waveform, so the incident pulse becomes a noise-like train of spikes. A simple method of creating pulsed lasers with either pulse-maintaining ultrabroad SC or specially shaped pulse waveforms can be implemented using all-normal-dispersion microstructured optical fibers (ANDi-MOFs). An ANDi-MOF with a simple topology and dispersion profile maximum at 800 nm was designed using the effective index method. Its properties and suitability were characterized via numerical simulation of femtosecond parabolic pulse formation and generation of an octave-spanning pulse-maintaining SC using a generalized propagation equation. The designed ANDi-MOF is suitable for resolving both problems and allows some detuning of the pulse’s wavelength around 800 nm. However, a better choice for SC generation is pumping at or near the wavelength where the third-order dispersion becomes zero. This configuration benefits from the absence of pulse break-up under large pulse energies, which appears otherwise. The fiber can provide a low-cost method for developing supercontinuum sources and a solution to the problems of parabolic waveform formation to meet the needs of optical signal processing and pulse amplification and compression.

Graphene Q-switched 0.9-\mu m Nd:La0.11Y0.89VO4 laser

Graphene saturable absorber (SA) is used as the passive Q-switcher of a 0.9-\mu m solid-state laser. When the laser medium is a Nd:La0.11Y0.89VO4 crystal, the initial transmittance of the graphene SA is 78%; at an absorbed pump power of 7.62 W, the maximum average output power, largest pulse energy, and minimum pulse width are 0.62 W, 2.58 ?J, and 84 ns, respectively. This study shows that graphene is a promising and cost-saving SA for 0.9-\mu m pulse generation.

Continuous-wave and actively Q-switched laser operations at 1359.5nm of Nd:LYSO crystal

The characteristics of continuous-wave and actively Q-switched laser operations at 1359.5 nm of (Nd 0.005 Lu 0.4975 Y 0.4975 ) 2 SiO 5 (Nd:LYSO) crystal were investigated. The maximum continuous-wave output power was 856 mW at an incident pump power of 8.32 W, corresponding to an optical conversion efficiency of 10.3% and a slope efficiency of 19.2%. By using an acousto-optical (AO) modulator, the Q-switched laser operation was realized. The maximum average output power, shortest pulse width, largest pulse energy and highest peak power of the Q-Switched laser were 534 mW, 45.1 ns, 92.4 µJ and 2.05 kW, respectively. • The characteristics of CW and actively Q-switched laser operations of Nd:LYSO disordered crystal are investigated. • This is the first demonstration that a Nd:LYSO laser operates at the 1.3 µm region. • A maximum Q-switched average output power of 534 mW is obtained. • The shortest pulse width is 45.1 ns and the highest peak power is 2.05 kW.

Bright broadband coherent fiber sources emitting strongly blue-shifted resonant dispersive wave pulses

We predict and realize the targeted wavelength conversion from the 1550-nm band of a fs Er:fiber laser to an isolated band inside 370-850 nm, corresponding to a blue-shift of 700-1180 nm. The conversion utilizes resonant dispersive wave generation in widely available optical fibers with good efficiency (~7%). The converted band has a large pulse energy (~1 nJ), high spectral brightness (~1 mW/nm), and broad Gaussian-like spectrum compressible to clean transform-limited ~17 fs pulses. The corresponding coherent fiber sources open up portable applications of optical parametric oscillators and dual-output synchronized ultrafast lasers.

The performance of 1329 nm CW and passively Q-switched Nd:LGGG laser with low Lu-doping level

The Nd:(LuxGd1−x)3Ga5O12 (Nd:LGGG) laser operating at 1329 nm in both the continuous wave (CW) and the passively Q-switched (PQS) regimes has been successfully demonstrated. With an absorbed pump power of 18.8 W, a maximum CW output power of 3.7 W was obtained, corresponding to an optical–optical conversion efficiency of 19.6% and a slope efficiency of 20.9%. The PQS laser performance was obtained using a V3+:YAG crystal as the saturable absorber. The maximum average output power, shortest pulse width, largest pulse energy and highest peak power were 0.75 W, 25.9 ns, 43.6 μJ and 1.7 kW, respectively. The results indicate that a Nd:LGGG crystal with a low Lu-doping level (0.66 at.%) could be a novel potential laser gain medium suitable for laser diode pumping and PQS operation at a wavelength of 1.3 μm.

Dual-wavelength synchronously Q-switched solid-state laser with multi-layered graphene as saturable absorber

Using multilayered graphene as the saturable absorber (SA), Nd:LYSO crystal as the laser material, we demonstrated a laser-diode (LD) pumped, dual-wavelength passively Q-switched solid-state laser. The maximum average output power is 1.8 W, the largest pulse energy and highest peak power is 11.3 μJ, 118 W, respectively. As we have known, they are the best results for passively Q-switched operation of graphene. The pulse laser is strong enough to realize extra-cavity frequency conversions. With a KTP crystal as the sum-frequency generator, the dual wavelengths are proved to be well time overlapped, which manifests the synchronous modulation to the dual-wavelength with multi-layered graphene.

LD端面泵浦Nd∶LiGd(MoO4)2晶体的主动调Q脉冲激光特性

The Nd∶LiGd(MoO4)2 crystal samples with different orientations were machined,and their Continuous Wave(CW) and actively modulation laser characteristics were measured and analyzed.A laser diode(LD) end-pumped double mirror cavity was used in the experiment,in which the coupling transmittance of the output mirror was 2%.In CW operation conditions,the maximum output powers of a-cut and c-cut crystals were 733 mW and 550 mW,respectively,corresponding optical conversion efficiencies of 11.3% and 6.7%.In acousto-optic(A-O) operation conditions,the maximum output powers of a-cut and c-cut crystals were 180 mW and 135mW,respectively,corresponding optical conversion efficiencies of 2.8% and 1.7%.The optimum pulse experimental results are obtained when the pulse repetition frequency(PRF) is 10 kHz.It is shown that the largest pulse energy and the highest peak power are 15.8 J and 85 W,respectively,which come from the a-cut sample.The shortest pulse width is 153 ns,which comes from the c-cut sample.Experimental results indicate that Nd∶LiGd(MoO4)2 crystals with different orientations can output different wavelengths in 1061 nm for the a-cut sample and in 1 068 nm for c-cut sample.The multi-wavelength emission property of the Nd∶LiGd(MoO4)2 crystal will help its applications to the THz-wave domain.

A diode-pumped passively Q-switched c-cut Nd:Lu0.1Y0.9VO4 laser

The continuous wave and pulsed laser performances of a laser-diode-end-pumped c-cut Nd:Lu0.1Y0.9VO4 crystal have been demonstrated for the first time. The small emission cross section and appropriate upper level lifetime result in the c-cut Nd:Lu0.1Y0.9VO4 crystals having excellent pulsed laser performance. When the pulse repetition rate was 6.4 kHz, the shortest pulse width, the largest pulse energy and the highest peak power were found to be 1.9 ns, 104.7 μJ and 55.1 kW, respectively, using a Cr4+:YAG crystal as the saturable absorber. These results were much better than those for an a-cut Nd:Lu0.1Y0.9VO4 crystal under the same conditions.

Diode-Pumped Actively Q-Switched Nd:Lu0.1Y0.9VO4Laser at 1.34 µm

The continuous-wave (CW) and acoustooptic (AO) Q-switched 1.34 µm laser performance of Nd:Lu0.1Y0.9VO4 crystals was demonstrated. In all operations, an a-cut crystal behaved better than a c-cut crystal. With a T = 3.9% output coupler, the maximum CW output power was 2 W, which corresponded to an optical conversion efficiency of 30.8%. At a pulse repetition frequency (PRF) of 5 kHz, the shortest pulse width, largest pulse energy, and highest peak power were 23.8 ns, 124 µJ, and 5.21 kW, respectively. As we have known, these are the best results obtained for a 1.34 µm pulsed laser based on mixed vanadate crystals.

Diode-Pumped Actively Q-Switched Nd:Lu0.1Y0.9VO4 Laser at 1.34 µm

The continuous-wave (CW) and acoustooptic (AO) Q-switched 1.34 µm laser performance of Nd:Lu0.1Y0.9VO4 crystals was demonstrated. In all operations, an a-cut crystal behaved better than a c-cut crystal. With a T = 3.9% output coupler, the maximum CW output power was 2 W, which corresponded to an optical conversion efficiency of 30.8%. At a pulse repetition frequency (PRF) of 5 kHz, the shortest pulse width, largest pulse energy, and highest peak power were 23.8 ns, 124 µJ, and 5.21 kW, respectively. As we have known, these are the best results obtained for a 1.34 µm pulsed laser based on mixed vanadate crystals.

Thermal and laser properties of Nd:Lu_3Sc_15Ga_35O_12 for high power dual-wavelength laser

We measured the thermal properties of Nd:Lu₃Sc₁.₅Ga₃.₅O₁₂ (Nd:LuSGG) crystal, including the thermal expansion coefficient, specific heat, and thermal diffusion coefficient. The calculated thermal conductivity is 4.4 W/mK at room temperature. A high-power continuous-wave and passively Q-switched Nd:LuSGG laser was also demonstrated. Continuous-wave output power of 6.96 W is obtained which is the highest power with this material. For the first time to our knowledge, the passively Q-switched Nd:LuSGG laser is reported with the shortest pulse width, largest pulse energy, and highest peak power are achieved to be 5.1 ns, 62.5 μJ, and 12 kW, respectively. By spectral analysis, it has been found that the Nd:LuSGG laser was located at 1059 nm under low pump power, and became dual-wavelength at 1061.5 and 1059 nm when the incident pump power is over 2.27 W. The generating mechanism of dual-wavelength laser is also discussed.

Growth and characterization of self-Q-switched Nd:Cr:YVO_4 crystal

A Nd:Cr:YVO4 crystal was grown by the Czochralski method for the first time to our knowledge. Its structure and cell parameter have been studied by X-ray powder diffraction (XRPD) analysis. Polarized absorption spectra were measured at room temperature, which showed that the absorption bands display polarization character and an absorption band of Cr5+ ions at 1110 nm enables the crystal to be a self-Q-switched laser material. We also found that the absorption of Cr5+ ions became much larger and its self-Q-switched laser performance became much better when the Nd:Cr:YVO4 crystal was annealed because the annealing induces more Cr ions to become those with + 5 valence. In the self-Q-switched laser, the maximum output power, shortest pulse width, and largest pulse energy were obtained to be 120 mW, 85.8 ns, and 0.79 μJ, respectively.

Cw and passively Q-switched laser performance of a mixed c-cut Nd:Gd 0.33Lu 0.33Y 0.33VO 4 crystal operating at 1.34 μm

Continuous wave and passively Q-switched laser operation with a mixed c-cut Nd:Gd 0.33Lu 0.33Y 0.33VO 4 crystal at 1.34 μm has been realized for the first time as far as we know. The largest output power of the continuous wave was 1.1 W for the output mirror of 5% transmission, with the optical conversion efficiency and the slope efficiency being 15% and 17.2%, respectively. The passive loss and the stimulated emission cross-section of the Nd:Gd 0.33Lu 0.33Y 0.33VO 4 crystal were found to be 0.6% and 0.47 × 10 −19 cm 2. The thermal lens effect that weakened the laser performance has also been measured. For passively Q-switched operation, the shortest pulse duration of 26 ns, the highest peak power of 1.8 kW, along with the pulse energy as large as 47 μJ, were obtained using V:YAG as Q-switch. The experimental results have shown that the passively Q-switched Nd:Gd 0.33Lu 0.33Y 0.33VO 4 laser can generate pulses with larger pulse energy and higher peak power in comparison with the passively Q-switched Nd:GdYVO 4 lasers.

Efficient, polarised, gain-switched operation of a Tm-doped fibre laser

We present a monolithic, robustly polarised thulium fibre laser which produces pulses with 25 ns duration and energy of up to 35 µJ. A pulsed 1.55 μm source was used to gain switch the laser at repetition rates of up to 300 kHz, producing average powers of up to 8 W at 2.044 µm. To the best of our knowledge this is the highest power gain-switched thulium fibre laser and it is also the first with a linearly polarised output. The large repetition rate, pulse energy and average power will enable efficient energy extraction from a large mode-area, polarisation maintaining thulium fibre amplifier.

Tri-wavelength laser with Nd:CLTGG crystal

Continuous-wave (CW) and passively Q-switched operations of laser diode-end-pumped Nd:CLTGG laser at 1.06 μm was demonstrated for the first time. The laser spectrum was found to be tri-wavelength, with respective wavelengths of 1058.4, 1060.5, and 1065.5 nm for both CW and passive Q-switching regime. The highest CW output power of 2.6 W was obtained with an optical-optical conversion efficiency of 13.9% and a slope efficiency of 17.1%. In the passive Q-switching regime, the highest output power, shortest pulse width, largest pulse energy and highest peak power were achieved as 242 mW, 45.8 ns, 1.65 μJ and 0.4 kW, respectively. The passively Q-switched tri-wavelength laser should have the potential to be used for terahertz radiation generation.

Diode-pumped continuous wave and Q-switched operation of Nd:LuAG crystal

The continuous wave (CW) and passively Q-switched performances of Nd:LuAG crystal were demonstrated. With a laser diode as pump source, the CW output power of 2.18 W was obtained under the pump power of 4.62 W, corresponding to the optical conversion efficiency of 47.2% and the slope efficiency of 52.2%. For Q-switching experiments, the shortest pulse width, largest pulse energy, and highest peak power were measured to be 12 ns, 50.6 μJ, and 4.21 kW, respectively.

Nd:YGG crystal laser at 1110 nm: a potential source for detecting carbon monoxide poisoning

We demonstrated a laser-diode pumped Nd-doped yttrium gallium garnet crystal laser at 1110 nm for the first time to our knowledge. By suppressing the oscillation at about 1.06 μm, continuous-wave output power of 2.1 W at 1110 nm was achieved. With a Cr:YAG as the saturable absorber, the passive Q-switching performance at this wavelength was obtained. The shortest pulse width and largest pulse energy were 31.5 ns and 22.7 μJ, respectively. Laser radiation at this wavelength is an important source for detecting carbon monoxide poisoning by simple frequency doubling with a nonlinear crystal.

Continuous-wave and passively Q-switched Nd:LYSO lasers

Continuous-wave (CW) and passively Q-switched performance of a Nd-doped oyorthosilicate mixing crystal, (Nd0.005Lu0.4975Y0.4975)2SiO5 (Nd:LYSO), were reported. As a result, new dual-wavelength all-solid-state lasers at 1075 and 1079 nm were achieved. When the absorbed pump power was 3.87 W, the CW laser produced 1.1 W output, corresponding to an optical conversion efficiency of 28.4% and a slope efficiency of 32.4%. By using a Cr4+:YAG wafer as the saturable absorber, we achieved Q-switching operation of Nd:LYSO crystal. The maximal average output power, shortest pulse width, largest pulse energy and highest peak power were measured to be 294 mW, 27.5 ns, 34.3 μJ and 1.18 kW, respectively. By difference frequency, these dual-wavelength lasers have potential applications for the generation of a broadband coherent radiation from 0.7–1.3 THz.

Spectroscopy of molecules in very high rotational states using an optical centrifuge

We have developed a high power optical centrifuge for measuring the spectroscopy of molecules in extreme rotational states. The optical centrifuge has a pulse energy that is more than 2 orders of magnitude greater than in earlier instruments. The large pulse energy allows us to drive substantial number densities of molecules to extreme rotational states in order to measure new spectroscopic transitions that are not accessible with traditional methods. Here we demonstrate the use of the optical centrifuge for measuring IR transitions of N2O from states that have been inaccessible until now. In these studies, the optical centrifuge drives N2O molecules into states with J ~ 200 and we use high resolution transient IR probing to measure the appearance of population in states with J = 93-99 that result from collisional cooling of the centrifuged molecules. High resolution Doppler broadened line profile measurements yield information about the rotational and translational energy distributions in the optical centrifuge.