Q-switched And Mode-locked Laser Research Articles

Numerical simulation for generation of stable single mode-locked pulses from QML laser with EO modulator and V3+:YAG

Abstract The instability of mode-locked pulses underneath Q-switched envelop limits the applications of Q-switched and mode-locked (QML) lasers. In this paper we present a developed theoretical model for QML laser at 1.3 µm. By adjusting the characteristics of the electro-optic modulator, V3+:YAG crystal, and laser resonator, stable single mode-locked pulse at 1.3 µm can be obtained at the pump power of 9 W. So far as we know, it is the first time to obtain single mode-locked pulses in QML laser at 1.3 µm by numerical simulation.

Passively Q-switched and mode-locked YVO4/Nd:YVO4/Nd:YVO4 laser based on a MoS2 saturable absorber at 1342.5 nm

We demonstrate a passively Q-switched and mode-locked (QML) laser with both YVO4/Nd:YVO4/Nd:YVO4 crystal and MoS2 saturable absorber (MoS2-SA) at ∼1342.5 nm. The MoS2-SA is fabricated with the liquid phase exfoliation (LPE) method. By inserting MoS2-SA into a Z-type resonator, we obtain a QML laser operation with the maximum average output power of 600 mW, the shortest envelope duration of 800 ns and the highest repetition rate of 98 kHz at 9 W. The energy of a Q-switched envelope is estimated to be about 6.12 μJ and the peak power is 39 W. The obtained envelope width and repetition rate are both superior to the results obtained from QML lasers with V3+:YAG and graphene at 1.34 μm. So far as we know, it is the first report on the QML laser at 1.34 μm with MoS2-SA, which proves the MoS2-SA is a good candidate for solid-state QML laser at 1.34 μm.

High Repetition Rate QML YVO4/Nd:YVO4/YVO4 Laser With a Reflective MoS2-SA

Two-dimensional (2D) materials have been proved to be excellent saturable absorbers. However, the study in Q-switched and mode-locked (QML) lasers has not shown good performances. In this letter, a reflective few-layer molybdenum disulfide saturable absorber (MoS 2 -SA) is fabricated. Using the reflective MoS 2 -SA, a nanosecond passively QML YVO 4 /Nd:YVO 4 /YVO 4 laser is experimentally demonstrated. At the pump power of 11 W, a stable QML laser operation can be achieved, corresponding to a repetition rate of 11 MHz, an envelope pulse width of 72 ns, and a modulation depth of 100%. So far as we know, it is the highest envelope repetition rate and the shortest envelope pulse duration in the reported QML lasers with 2D materials, which prove the MoS 2 -SA has excellent optical properties for ultrafast solid-state laser applications.

1.1 MW peak power in doubly QML composite Nd:YVO4/Nd:YVO4/Nd:YVO4/KTP sub-nanosecond green laser with EO and Bi-GaAs.

By simultaneously employing electro-optic (EO) modulator and Bi-doped GaAs, dual-loss-modulated Q-switched and mode-locked (QML) multi-segment composite Nd:YVO4/Nd:YVO4/Nd:YVO4/KTP sub-nanosecond green laser is demonstrated with low repetition rate and high peak power. When the incident pump power is up to 6.93 W, only one mode-locking pulse underneath a Q-switching envelope is generated with sub-nanosecond pulse duration at one kilohertz repetition rate. An average output power of 445 mW and a pulse duration of 399 ps are obtained with the incident pump power of 11.13 W, corresponding to a peak power of 1.115 MW which is the highest one in doubly QML sub-nanosecond green laser by now. The laser characteristics are better than those obtained with EO and GaAs. The experimental results indicate that Bi-GaAs is a promising saturable absorber for dual-loss-modulated QML laser.

Dual-loss-modulated Q-switched mode-locked laser intracavity pumped temperature-tuned subnanosecond KTiOPO4 optical parametric oscillator.

Using an acousto-optic modulator (AOM) and Cr4+:YAG as the dual-loss modulation, an intracavity KTiOPO4 optical parametric oscillator (OPO) pumped by a simultaneously Q-switched and mode-locked (QML) YVO4/Nd:YVO4 laser was realized. The shortest mode-locking pulse duration of the signal wave at 1573 nm was directly measured as 450 ps at an AOM frequency of 2 kHz and a diode pump power of 10.5 W, corresponding to a peak power of 35.5 kW. The temperature tuning of the output signal wavelength was realized in the range from 1571.99 to 1572.61 nm with a blueshift ratio of 0.027 nm/°C. A set of coupled rate equations for the dual-loss-modulated QML laser pumping intracavity OPO was built for the first time to our knowledge. The numerical solutions were fitted with the experimental results.

Passively Q-switched and mode-locked Nd:GGG laser with a Bi-doped GaAs saturable absorber.

A simultaneously passively Q-switched and mode-locked (QML) Nd:GGG laser using a Bi-doped GaAs wafer as saturable absorber is accomplished for the first time. The Bi-doped GaAs wafer is fabricated by ion implantation and subsequent annealing. In comparison to the passively QML laser with GaAs, the QML laser with Bi-doped GaAs can generate more stable pulses with 99% modulation depth. The experiment results indicate that the Bi-doped GaAs could be an excellent saturable absorber for diode-pumped QML lasers.

Intracavity-frequency-doubled Q-switched and mode-locked Nd:Lu0.15Y0.85VO4/KTP green laser with AO modulator and central SESAM

By using mixed crystal Nd:Lu0.15Y0.85VO4 as laser medium, KTP as frequency-doubling crystal, a diode-pumped intracavity-frequency-doubled Q-switched and mode-locked (QML) Nd:Lu0.15Y0.85VO4/KTP green laser with acousto-optic (AO) modulator and central semiconductor saturable absorption mirror (C-SESAM) is realized by using a V-type cavity. The QML laser characteristics such as the pulse width, single-pulse energy, have been measured for different modulation frequencies of the AO modulator. In comparison with the singly passively QML green laser with central SESAM, the doubly QML green laser can generate more stable and shorter pulses with higher peak power. Based on the coupled rate equations for a diode-pumped doubly QML green laser with AO and C-SESAM, in which the saturated absorption mechanism of C-SESAM is considered, the recurrence relation of the relative amplitude of the mode-locking pulses is given and the related numerical simulations are in good agreement with the experimental results.

Low repetition rate subnanosecond pulse laser generation from a diode pumped Nd:Lu_3Al_5O_12 laser with electro-optic modulator and transmission semiconductor saturable absorber

By using the dual-loss modulated technology, i.e., adopting the electro-optic (EO) modulator and transmission semiconductor saturable absorber (transmission SSA) simultaneously, a diode-pumped doubly Q-switched and mode-locked (QML) Nd:Lu3Al5O12 (Nd:LuAG) laser at 1.06 μm has been realized for the first time. In comparison to the singly passively QML Nd:LuAG laser with transmission SSA, the doubly QML laser can generate more stable pulses with shorter pulse widths and higher peak powers. It can also be observed that the pulse duration of the Q-switched envelope decreases with increasing pump power. When the pump power exceeds 6.52 W for the first time, there is only one mode-locked pulse underneath a Q-switched envelope for this doubly QML Nd:LuAG laser. As a result, the subnanosecond pulse laser with 1 kHz repetition rate of EO and high stability can be generated. The shortest pulse duration generated is about 718 ps and the highest peak power reaches as high as 502 kW. The experimental results show that Nd:LuAG is an excellent alternative crystal for diode-pumped QML pulsed laser generation.

Optimization of diode-pumped doubly Q-switched mode-locked laser with electro-optic modulator and GaAs saturable absorber

In this paper, by considering Gaussian distribution of the intracavity photon density, the coupled rate equations for the diode-pumped doubly Q-switched and mode-locked (QML) laser with EO modulator and GaAs saturable absorber are presented. These equations are numerically solved, and the key parameters of an optimally coupled doubly QML laser have been determined. These key parameters include parameters of the gain medium, the small-signal transmission of saturable absorber as well as the modulation frequency of EO modulator, which can maximize the pulse energy of singly Q-switched envelope. A diode-pumped doubly QML Nd:Lu0.15Y0.85VO4 laser with EO modulator and GaAs saturable absorber is constructed, the experimental results have verified numerical simulation applicable.

Performance of doubly Q-switched and mode-locked Nd:Lu0.33Y0.37Gd0.3VO4 and Nd:Lu0.5Y0.5VO4 lasers with acousto-optic modulator and GaAs saturable absorber

By using Nd:YVO4, Nd:Lu0.5Y0.5VO4 and Nd:Lu0.33Y0.37Gd0.3VO4 crystals as laser media, the diode-pumped singly passively Q-switched and mode-locked (QML) lasers with GaAs saturable absorber, and the doubly QML lasers with acousto-optic (AO) modulator as well as GaAs are presented. In comparison with the singly passively QML laser with GaAs, the doubly QML lasers can generate stable pulse train, shorter pulse width, greater pulse energy and higher peak power. The experimental results show that the Nd:Lu0.33Y0.37Gd0.3VO4 QML laser can generate shorter pulse width with higher peak power than the Nd:YVO4 or Nd:Lu0.5Y0.5VO4 QML laser.

Diode-pumped Q-switched and mode-locked Nd:Lu3Al5O12 lasers

By using Nd:Lu3Al5O12 (Nd:LuAG) as the gain medium, GaAs as a passive saturable absorber and an acousto-optic (AO) modulator as an active Q-switch, a diode-pumped singly passively Q-switched and mode-locked (QML) Nd:LuAG laser saturable with GaAs and a doubly QML Nd:LuAG laser with GaAs and an AO are realized for the first time. The laser characteristics of the QML pulses have been measured. In comparison to the singly passively QML laser with GaAs, the doubly QML laser with AO and GaAs can generate more stable pulses with higher peak power. The experimental results show that Nd:LuAG is an excellent alternative crystal for diode-pumped QML pulsed generation.

Passively Q-switched and mode-locked laser performance of the mixed crystals with GaAs saturable absorber

By using the mixed crystals Nd:Lu0.33Y0.37Gd0.3VO4, Nd:Lu0.5Y0.5VO4 and Nd:Lu0.15Y0.85VO4 as laser media, the LD pumped passively Q-switched and mode-locked (QML) lasers with GaAs saturable absorber are realized. The average output power, the pulse width and the repetition rates have been measured and compared. The experimental results show that the passively Q-switched and mode-locked Nd:Lu0.33Y0.37Gd0.3VO4 laser can generate shorter pulse width with higher peak power due to broader fluorescence line-width. By considering the Gaussian distribution of the intracavity photon density and the influence of the continuous pump rate, the coupled rate equations for QML lasers with GaAs saturable absorber are given. The theoretical solutions of the equations are in agreement with the experimental results.

Improvements of pulse energy and symmetry of diode-pumped hybrid Q-switched mode-locked Nd:Lu0.15Y0.85VO4 laser at 1.34 μm

Diode-pumped hybrid Q-switched and mode-locked (QML) Nd:Lu0.15Y0.85VO4 laser operating at 1.34μm with acousto-optic (AO) modulator and Co:LMA saturable absorber has been demonstrated. The symmetry of the Q-switched envelopes with the hybrid QML is evidently improved in comparison with the single QML. The hybrid QML laser can obtain a modulation depth of nearly 100%. The experimental results show that with the hybrid QML the output Q-switched pulse energy increases to 923% and the Q-switched pulse width reduces to 18%, if compared with the single passively QML.

Optimization of diode-pumped doubly Q-switched mode-locked laser with acousto-optic modulator and <inline-formula><math display="inline" overflow="scroll"><mrow><msup><mrow><mi>Cr</mi></mrow><mrow><mn mathvariant="bold">4</mn><mo>+</mo></mrow></msup><mo>∶</mo><mi>YAG</mi></mrow></math></inline-formula> saturable absorber

By considering the influence of the turn-off time and the modulation frequency of the acousto-optic (AO) modulator, the coupled rate equations for a diode-pumped doubly Q-switched and mode-locked (QML) laser with AO modulator and Cr4+∶YAG saturable absorber under Gaussian approximation are given. By numerically solving these equations, the key parameters of an optimally coupled doubly QML laser including the gain medium, the saturable absorber and the resonator as well as the modulation frequency of AO modulator are obtained, which can maximize the pulse energy of singly Q-switched envelope. A diode-pumped doubly QML Nd∶GdVO4 laser with AO modulator and Cr4+∶YAG saturable absorber is constructed and the experimental results are in agreement with the numerical simulations.

Improvement of stability and pulse energy in a diode-pumped dual-loss-modulated QML Nd:Lu0.2Y0.8VO4 laser with EO modulator and GaAs

The Q-switched and mode-locked (QML) performance in a diode-pumped Nd:Lu0.2Y0.8VO4 laser with electro-optic (EO) modulator and GaAs saturaber absorber is investigated. In comparison with the solely passively QML laser with GaAs, the dual-loss-modulated QML laser with EO and GaAs can generate pulses with higher stability and shorter pulse width of Q-switched envelope, as well as higher pulse energy. At the repetition rate 1kHz of EO, the pulse width of Q-switched pulse envelope has a compression of 89% and the pulse energy has an improvement of 24 times. The QML laser characteristics such as the pulse width, pulse peak power etc. have been measured for different small-signal transmittance (T0) of GaAs, different reflectivity (R) of output coupler and modulation frequencies of the EO modulator (fe). The highest peak power and the shortest pulse width of mode-locked pulses are obtained at fe=1kHz, R=90% and T0=92.6%. By considering the influences of EO modulator, a developed rate equation model for the dual-loss-modulated QML laser with EO modulator and GaAs is proposed. The numerical solutions of the equations are in good agreement with the experimental results.

Experimental study on doubly QML Nd:Lu0.15Y0.85VO4 laser with AO modulator and central SESAM

By using double-mixed crystal Nd:Lu0.15Y0.85VO4 as laser medium, a diode-pumped doubly Q-switched and mode-locked (QML) Nd:Lu0.15Y0.85VO4 laser with acousto-optic (AO) modulator and central semiconductor saturable absorption mirror (SESAM) is realized for the first time. The Q-switched envelope modulation depth is nearly 100%.The average output power and the pulse width of the Q-switched envelope etc. for different AO modulator repetition rates have been measured. The experimental result show that Nd:Lu0.15Y0.85VO4 crystal is an excellent laser medium for doubly QML lasers.

Diode-pumped Q-switched and mode-locked Nd:Gd 0.3Lu 0.33Y 0.37VO 4 laser with EO modulator and single-walled carbon nanotube

By using both the single-walled carbon nanotube saturable absorber (SWCNT-SA) and the electro-optic (EO) modulator, the stably doubly Q-switched and mode-locked (QML) operation of Nd:Gd 0.3Lu 0.33Y 0.37VO 4 laser has been demonstrated. The QML laser characteristics such as the pulse width, single-pulse energy, etc., have been measured for different modulation frequencies of the EO modulator ( f e ) and reflectivity ( R) of output coupler. In comparison with the solely passively QML laser with SWCNT-SA, the experimental results show that the doubly QML laser can generate more stable and shorter pulses with higher pulse energy. At 9.24 W pump power, f e =1 kHz and R=93.5%, the doubly QML laser has compressed the Q-switched envelope pulse width 88% and improved the mode-locked pulsed energy 55 times.

Double-loss-modulated q-switched and mode-locked Nd:Lu0.15Y0.85VO4 laser at 1.34 μm with single-walled carbon nanotube saturable absorber and AO modulator

A diode-pumped dual-loss-modulated Q-switched and mode-locked (QML) Nd:Lu0.15Y0.85VO4 laser at 1.34 μm with single-walled carbon nanotube saturable absorber (SWCNT-SA) and acousto-optic (AO) modulator is demonstrated. The modulation depth of the dual-loss-modulated QML laser reaches 90%, being deeper than 75% that obtained by the single passively QML laser. The stability of the hybrid QML laser is significantly improved if compared to that only with SWCNT-SA. The Q-switched pulse energy and the Q-switched pulse width of the QML laser with the dual-loss-modulation are 487 and 27% of those only with SWCNT-SA, respectively.

Optimization of the pulse-width of diode-pumped passively Q-switched mode-locked c-cut Nd:GdVO_4 laser with a GaAs saturable absorber

By considering the single-photon absorption and two-photon absorption processes in the GaAs saturable absorber, the coupled rate equations for a diode-pumped passively Q-switched and mode-locked (QML) laser with GaAs coupler under Gaussian approximation are given. These rate equations are solved numerically. The key parameters of an optimally coupled passively QML laser with the shortest pulse-width envelope are determined. These key parameters include the parameters of the gain medium, the saturable absorber, and the resonator, which can minimize the pulse-width of a singly Q-switched envelope. Sample calculations for a diode-pumped passively Q-switched mode-locked c-cut Nd:GdVO(4) laser with a GaAs coupler are presented to demonstrate that the shortest pulse-width envelope can be obtained by selecting the optimal small-signal transmission of the saturable absorber and the reflectivity of the output mirror.

Enhancement of stability and peak power in a diode-pumped doubly QML YVO 4/Nd:YVO 4 laser with EO and Cr 4+:YAG saturable absorber

A diode-pumped doubly Q-switched and mode-locked (QML) YVO 4/NdYVO 4 laser is realized with the electro-optic (EO) modulator and Cr 4+:YAG saturable absorber, in which the repetition rate of the Q-switched envelope is controlled by the active EO modulation while the mode-locked pulses inside the Q-switched envelope depend on both the actively modulated loss and the passive saturable absorption. The experimental results show that the doubly QML laser can generate more stable and shorter pulses with higher peak power when compared with the singly passively QML laser with Cr 4+:YAG. At the pump power of 20 W and the repetition rate 1 kHz, a 21 ns Q-switched pulse envelope with a average mode-locked peak power of 544 kW is obtained, which is the shortest Q-switched pulse envelope to my knowledge. In comparison to the singly passively QML laser with Cr 4+:YAG, the doubly QML laser has compressed the Q-switched envelope pulse width 70% and improved the mode-locked pulsed peak power 27 times. By using a hyperbolic secant square function and considering the Gaussian distribution of the intracavity photon density, the coupled equations for diode-pumped dual-loss-modulated QML laser is given and the numerical solutions of the equations are in good agreement with the experimental results.