Diode-pumped passively Q-switched and mode-locked Nd:Lu<Subscript>0.15</Subscript>Y<Subscript>0.85</Subscript>VO<Subscript>4</Subscript> laser with a GaAs saturable absorber

By using a-cut Nd:Lu_0.15Y_0.85VO₄ mixed crystal as laser gain medium, a diode-pumped passively Q-switched and mode-locked (QML) laser with a GaAs saturable absorber in a Z-type folded cavity is demonstrated for the first time. The Q-switched mode-locked laser pulses with about 90% modulation depth are obtained as long as the pump power reached the oscillation threshold. The repetition rate of the passively Q-switched pulse envelope ranges from 50 to 186 kHz as the pump power increases from 0.915 to 6.520 W. Under an incident pump power of 6.52 W, the QML pulses with the largest average output power of 694 mW, the shortest pulse width of 200 ns and the highest pulse energy of 3.73 μJ are obtained. The mode-locked pulse width inside the Q-switched envelope is estimated to be about 275 ps. The experimental results show that Nd:Lu_0.15Y_0.85VO₄ is a promising mixed crystal for QML laser.     

Experimental study on doubly QML Nd:Lu<Subscript>0.15</Subscript>Y<Subscript>0.85</Subscript>VO<Subscript>4</Subscript> laser with AO modulator and central SESAM

By using double-mixed crystal Nd:Lu_0.15Y_0.85VO₄ as laser medium, a diode-pumped doubly Q-switched and mode-locked (QML) Nd:Lu_0.15Y_0.85VO₄ 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:Lu_0.15Y_0.85VO₄ crystal is an excellent laser medium for doubly QML lasers.     

Actively Q-switched laser performance comparison between Nd:Lu0.15Y0.85VO4 and Nd:Lu0.33Y0.37Gd0.3VO4 mixed crystals

By using acousto-optic (AO) modulator as active Q-switch, the diode-pumped actively Q-switched Nd:Lu_0.15Y_0.85VO₄ and Nd:Lu_0.33Y_0.37Gd_0.3VO₄ lasers are realized. The average output power and the pulse width under different AO repetition rates are measured. The actively Q-switched laser performances for two kind mixed crystals are compared for the first time. The experimental results show that the actively Q-switched Nd:Lu_0.33Y_0.37Gd_0.3VO₄ laser can generate shorter pulse width with higher peak power in comparison with the actively Q-switched Nd:Lu_0.15Y_0.85VO₄ laser. Due to broader fluorescence line-width, the triple-mixed crystal Nd:Lu_0.33Y_0.37Gd_0.3VO₄ is a promising laser medium for shorter Q-switched pulse with higher peak power.     

Passively Q-switched laser performance of the mixed crystals Nd:Lu0.15 Y0.85 VO4, Nd:Lu0.5 Y0.5 VO4 and Nd:Lu0.33Y0.37Gd0.3VO4 with GaAs saturable absorber

By using the mixed crystals Nd:Lu_0.15 Y_0.85 VO₄, Nd:Lu_0.5Y_0.5VO₄ and Nd:Lu_0.33Y_0.37Gd_0.3VO₄ as laser media, the LD pumped passively Q-switched mixed lasers with GaAs saturable absorber are realized. The average output power, the pulse width etc. have been measured and compared. The experimental results show that the passively Q-switched Nd:Lu_0.33Y_0.37Gd_0.3VO₄ laser can generate shorter pulse width with higher peak power due to broader fluorescence line-width. Under Gaussian spatial distribution approximation, the rate equations for LD pumped passively Q-switched lasers of the mixed crystals with GaAs saturable absorber are given. The numerical solutions of the equations are in agreement with the experimental results.     

Diode-pumped Q-switched Nd:Y<Subscript>0.5</Subscript>Lu<Subscript>0.5</Subscript>VO<Subscript>4</Subscript> laser double-modulated with an acousto-optic modulator and Cr<Superscript>4+</Superscript>:YAG saturable absorber

A diode pumped Nd:Y_0.5Lu_0.5VO₄ pulse laser modulated with an acousto-optic (AO) Q-switcher and Cr⁴⁺:YAG saturable absorber is first demonstrated in this paper. The laser is shown to generate shorter pulse width than AO Q-switched laser alone, and have a higher peak power and single pulse energy than passively Q-switched laser with only Cr⁴⁺:YAG. A laser pulse width of 6.16 ns and a peak power of about 43.83 kW are achieved at the incident pumping power of 14.09 W.     

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

By using the mixed crystals Nd:Lu_0.33Y_0.37Gd_0.3VO₄, Nd:Lu_0.5Y_0.5VO₄ and Nd:Lu_0.15Y_0.85VO₄ 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:Lu_0.33Y_0.37Gd_0.3VO₄ 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.     

Performance comparisons of passively Q-switched intracavity-frequency-doubled Nd:Gd<Subscript>0.19</Subscript>Y<Subscript>0.81</Subscript>VO<Subscript>4</Subscript> and Nd:Gd<Subscript>0.83</Subscript>Y<Subscript>0.17</Subscript>VO<Subscript>4</Subscript> lasers at 671 nm

Performance comparisons of laser-diode pumped passively Q-switched intracavity-frequency-doubled Nd:Gd_0.19Y_0.81VO₄ and Nd:Gd_0.83Y_0.17VO₄ lasers at 671 nm are demonstrated for the first time to our knowledge. KTP crystal is used as the frequency doubling material and V:YAG crystal as the saturable absorber with initial transmission of 89%. The dependences of average output power, pulse width, pulse repetition rate, single-pulse energy and peak power on incident pump power are measured and contrasted. The experimental results show that, Nd:Gd_0.83Y_0.17VO₄ laser has more excellent properties than Nd:Gd_0.19Y_0.81VO₄ laser at 671 nm.     

Crystal growth,spectroscopic characterization and laser performance of Nd:Lu<Subscript>0.33</Subscript>Y<Subscript>0.36</Subscript>Gd<Subscript>0.3</Subscript>VO<Subscript>4</Subscript> crystal

A new three-matrix mixed vanadate crystal Nd:Lu_0.33Y_0.36Gd_0.3VO₄ (Nd:LuYGdVO₄) crystal was grown by the Czochralski method. Room temperature absorption and fluorescence spectra of the Nd:LuYGdVO₄ crystals were measured and the spectroscopic parameters were calculated by the Judd-Ofelt theory. The intensity parameters of the Nd:LuYGdVO₄ crystal were Ω₂ = 9.736 × 10⁻²⁰ cm², Ω₄ = 4.179 × 10⁻²⁰ cm², Ω₆ = 8.020 × 10⁻²⁰ cm² and the stimulate emission cross section was 5.3 × 10⁻¹⁹ cm². Diodepumped actively Q-switched and passively Q-switched Nd:LuYGdVO₄ and Nd:Lu_0.14Y_0.86VO₄ lasers at 1.06 μm were demonstrated. The results indicate that, for both actively and passively Q-switched lasers, the Nd:LuYGdVO₄ lasers can generate shorter pulse width with higher peak power than the Nd:Lu_0.14Y_0.86VO₄ lasers at the same cavity conditions.     

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:Lu_0.15Y_0.85VO₄ as laser medium, KTP as frequency-doubling crystal, a diode-pumped intracavity-frequency-doubled Q-switched and mode-locked (QML) Nd:Lu_0.15Y_0.85VO₄/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.     

Study of LD pumped Q-switched Nd:Y<Subscript>0.5</Subscript>Lu<Subscript>0.5</Subscript>VO<Subscript>4</Subscript> laser with acousto-optic modulator

A laser-diode (LD) pumped Q-switched Nd:Y_0.5Lu_0.5VO₄ crystal laser with an acousto-optic (AO) modulator is presented in this paper. The maximum continuous wave (CW) output power of 5.53 W is achieved at the incident pump power of 14.09 W with the transmission of 10% for the output coupler, resulting in an optical-to-optical conversion efficiency of 39.2%. For Q-switching operation, the shortest pulse width of 8.3 ns and the highest peak power of 259 kW are generated under the incident pump power of 14.09 W at 1 kHz.     

Diode-pumped actively Nd:Lu0.33Y0.37Gd0.3VO4 Q-switched laser with electro-optic (EO) modulator

Nd:Lu_0.33Y_0.37Gd_0.3VO₄ crystal is a new triple-mixed vanadate crystal and has broader fluorescence line-width. By using electro-optic (EO) modulator as active Q-switch, a diode-pumped actively Q-switched Nd:Lu_0.33Y_0.37Gd_0.3VO₄ laser is realized for the first time. The average output power and the pulse width under different EO repetition rates are measured. The experimental results show that the actively Q-switched Nd:Lu_0.33Y_0.37Gd_0.3VO₄ laser can generate shorter pulse width with higher peak power. Due to broader fluorescence line-width, the triple-mixed crystal Nd:Lu_0.33Y_0.37Gd_0.3VO₄ is a promising laser medium for the Q-switched laser.     

Passively Q-switched laser performance of Nd:Lu<Subscript>0.15</Subscript>Y<Subscript>0.85</Subscript>VO<Subscript>4</Subscript> operating at 1.34 μm with a V:YAG saturable absorber

A diode-pumped passively Q-switched Nd:Lu_0.15Y_0.85VO₄ crystal laser at 1.34 μm with V:YAG employed as the saturable absorber was demonstrated for the first time to our best knowledge. The maximum average output power of 0.529 W was achieved under the pump power of 5.6 W, corresponding to an opticaloptical conversion efficiency of over 9.4% and slope efficiency of over 16%. The pulse width was shortened to 85.6 ns, corresponding to the maximum pulse repetition rate of 250 kHz. The largest single pulse energy and peak power were 5.57 μJ and 58.74 W, respectively.     

Characteristics of diode-pumped dual-loss-modulated Q-switched and mode-locked Nd:Lu<Subscript>0.15</Subscript>Y<Subscript>0.85</Subscript>VO<Subscript>4</Subscript> laser

A diode-pumped dual-loss-modulated Q-switched and mode-locked (QML) Nd:Lu_0.15Y_0.85VO₄ laser with acousto-optic (AO) modulator and Cr⁴⁺:YAG saturable absorber is presented. The stable QML laser pulse with high peak power and complete modulation depth has been obtained. The QML laser characteristics such as the pulse width, single-pulse energy etc. have been measured for different small-signal transmissions (T ₀) of Cr⁴⁺:YAG, different reflectivity (R) of output coupler and modulation frequencies of the AO modulator (f _p ). The results show that the pulse energy increases with decreasing f _p and increasing T ₀, while the pulse width decreases with decreasing f _p and increasing T ₀. At f _p = 10 kHz, R = 90%, and T ₀ = 91%, the highest pulse energy and peak power of mode-locked pulses is obtained.     

Passively Q-switched laser operation in a composite Nd:YVO<Subscript>4</Subscript>/Nd:YVO<Subscript>4</Subscript>/Nd:YVO<Subscript>4</Subscript> crystal with a single-walled carbon nanotube saturable absorber

By using a piece of single-walled carbon nanotube saturable absorber, the performance of the passively Q-switched composite Nd:YVO₄ laser has been demonstrated for the first time. The maximum average output power and the shortest pulse width are 1220 mW and 103 ns at the incident pump power of 5.04 W for a 10% transmission of the output coupler. The highest pulse repetition rate of 415.6 kHz and the largest single-pulse energy of 2.94 μJ are also obtained. The composite Nd:YVO₄ crystal has more excellent laser performance than the normal Nd:YVO₄ crystal at 1064 nm.     

Double-loss-modulated q-switched and mode-locked Nd:Lu<Subscript>0.15</Subscript>Y<Subscript>0.85</Subscript>VO<Subscript>4</Subscript> 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:Lu_0.15Y_0.85VO₄ 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.     

Actively Q-switched performance of a mixed crystal Nd:Lu<Subscript>0.5</Subscript>Y<Subscript>0.5</Subscript>VO<Subscript>4</Subscript> at 1.34 μm

The actively Q-switched laser performance of the mixed Nd:Lu_0.5Y_0.5VO₄ crystal was demonstrated for the first time. At the pump power of 7.26 W, the minimum pulse width of 46.6 ns was obtained at the pulse repetition rate of 5 kHz with the cavity length of 80 mm, and the single pulse energy and peak power were calculated to be 42 μJ and 901.3 W, respectively.     

Systematic study on thermal lens effect and passive Q-switching of diode-pumped 1.34-μm Nd:GdxY1 ? xVO4 laser with different output couplers

The thermal lens effect and passively Q-switched laser performance of mixed Nd:Gd _x Y_{1 − x} VO₄ crystals at 1.34 μm with 5 and 10% as the output transmissions have been systematically studied. Compared with the single vanadate crystal Nd:GdVO₄, the mixed Nd:Gd _x Y_{1 − x} VO₄ crystals can enhance passively Q-switched laser characteristics due to their smaller emission cross sections, although they have stronger thermal lens effects which result in decreasing the average output power. The largest peak power and pulse energy, obtained for Nd:Gd_0.63Y_0.37VO₄, were 2.9 and 1.7 times as those of Nd:GdVO₄ under the uniform conditions.     

Diode-pumped passively Q-switched Nd:LuxY1−xVO4 laser at 1.34 μm with two V:YAG saturable absorbers

Laser performance with the mixed Nd:Lu_0.15Y_0.85VO₄ crystal at 1.34 μm wavelength has been demonstrated. The continuous wave (cw) operation was carried out in a simple plano-concave resonator with an optical conversion efficiency of 23% and a slop efficiency of 25%. At a pump power of 6.78 W, the Q-switched pulses with the largest average output power of 349 mW, the shortest pulse width of 30.6 ns, the largest repetition rate of 42.5 kHz, the highest peak power of 268 W and the largest pulse energy of 8.2 μJ were obtained, corresponding to the V:YAG with initial transmission of 89%.     

Timing-jitter reduced high-repetition-rate Q-switched Nd:YVO<Subscript>4</Subscript>/Cr<Superscript>4+</Superscript>:YAG micro laser with low pump power

We report a high repetition rate Q-switched Nd:YVO₄/Cr⁴⁺:YAG micro laser with small pump power. Unwanted defects in pulse train, which are inherently large in passively Q-switched laser, was simply minimized by controlling temperature of Nd:YVO₄/Cr⁴⁺:YAG medium. When T ₀ = 90% Cr⁴⁺:YAG and R _OC = 90% output coupler were used, Q-switched Nd:YVO₄/Cr⁴⁺:YAG micro laser showed the optimum output; maximum output power of 58 mW, optical-to-optical efficiency of 9.1%, repetition rate of 1.1 MHz, and pulse width of 57 ns were achieved with 640 mW pumping. MHz-order repetition rate in Nd:YVO₄/Cr⁴⁺:YAG Q-switched laser with low pumping (<1 W) is the highest value to the best of our knowledge.     

High-power passively Q-switched Nd:YVO<Subscript>4</Subscript> UV laser at 355 nm

We report on an efficient high-power passively Q-switched UV laser at 355 nm. We take into account the second threshold criterion and the thermal-lensing effect to design and realize a compact reliable passively Q-switched Nd:YVO₄ laser with Cr⁴⁺:YAG as a saturable absorber. At an incident pump power of 16.3 W, the average output power at 1064 nm reaches 6.2 W with a pulse width of 7 ns and a pulse repetition rate of 56 kHz. Employing the developed passively Q-switched laser to perform the extra-cavity harmonic generations, the maximum average output powers at 532 nm and 355 nm are up to 2.2 W and 1.62 W, respectively.