Fabrication of aligned single wall carbon nanotube absorbers for high power passive mode-locked Nd:GdVO<Subscript>4</Subscript> laser

Using the vertical evaporation technique we fabricated saturable absorbers by transferring the water-soluble single wall carbon nanotubes (SWCNT) onto a hydrophilic quartz substrate. The fast recovery times of the absorber were measured to be 136 and 790 fs. The modulation depth of the absorber was about 2%. Passive mode-locked Nd:GdVO₄ laser using such an absorber was demonstrated. The continuous wave mode-locked pulses with the pulse duration of 12.4 ps and the repetition of 120 MHz were achieved. The maximum average output power of the mode-locked laser is 2.4 W at the pump power of 13 W. Such kind of absorber has potential to be put into practical use for high power solid-state laser mode locking.     

A passively mode-locked Nd:YVO<Subscript>4</Subscript> laser with a carbon nanotube saturable absorber

We report the mode locking of a diode pumped Nd:YVO₄ crystal laser by using a transmission-type single-walled carbon nanotube saturable absorber. The laser operated at 1064 nm pumped by a fiber coupled laser diode with the cavity length of 1826 mm, generated a pulse width of 14 ps at a repetition rate of 82 MHz. The output power of 120 mW was obtained at the absorbed pumping power of 1400 mW.     

Passive mode-locked Nd:YVO<Subscript>4</Subscript> laser using a multi-walled carbon nanotube saturable absorber

We report a passive mode-locked Nd:YVO₄ laser pumped by 880 nm LD using a transmission-type multi-walled carbon nanotube saturable absorber. At the pump power of 6.1 W, the average output power of 0.8 W of continuous wave mode-locked laser with optical conversion efficiency of 13.1% was generated. The repetition rate and pulse energy of the mode-locked pulse were 88 MHz and 9.1 nJ, respectively.     

Diode-pumped passively mode-locked Nd:GdVO<Subscript>4</Subscript> laser with a GaAs saturable absorber mirror

We report on a diode end-pumped passively mode-locked Nd:GdVO₄ laser. By using a GaAs wafer simultaneously as the saturable absorber and the output coupler, stable continuous-wave mode locking was achieved. The pulse width was measured to be 18.9 picoseconds at a repetition rate of 370 MHz. The most remarkable property of the laser is that its repetition rate can be changed from 370 MHz to 3.348 GHz by simply changing the cavity length. An average output power of 3.46 W at a 3.348 GHz repetition rate was obtained with a 14 W pump power. To our knowledge, this is the first demonstration of a passively mode-locked Nd:GdVO₄ laser using a GaAs wafer as the saturable absorber. PACS 42.55.Rz; 42.60.Fc; 42.55.Xi.     

880 nm LD pumped passive Q-switched and mode-locked Nd:YVO<Subscript>4</Subscript> laser using a single-walled carbon nanotube saturable absorber

We report a 880 nm LD pumped passive Q-switched and mode-locked Nd:YVO₄ laser using a single-walled carbon nanotube saturable absorber (SWCNT-SA). At the pump power of 7.78 W, the average out-put power of 330 mW of Q-switched and mode-locked laser with optical conversion efficiency of 4.2% was generated. The repetition rate and pulse width of the Q-switched envelope were 33 kHz and 5.6 μs, respectively. The repetition rate and pulse energy of the mode-locked pulse within the Q-switched envelope were 80 MHz and 4.1 nJ, respectively.     

Cavity-dumped mode-locked Nd:GdVO<Subscript>4</Subscript> laser at low repetition rate

We report a cavity-dumped mode-locked Nd:GdVO₄ laser with semiconductor saturable absorber mirrors at low repetition rate. In this laser system, a single mode-locked laser pulse is generated, amplified and cavity-dumped by means of electro-optic modulator at 1 to 10 Hz repetition rate. The energy of the pulse is about 150 nJ and the pulse duration is determined to be 10 ps.     

Diode-pumped passively Q-switched and Q-switch mode-locked Nd:YVO<Subscript>4</Subscript> laser using single-wall carbon nanotube based saturable absorber

We present the performance of diode end-pumped Nd:YVO₄ laser in Q-switched and Q-switched mode-locking oscillation using a single-walled carbon nanotube based saturable absorber, which was fabricated using similar vertical evaporation technique. The average output power, repetition rate and pulse width of the Q-switched laser output were studied with different output couplers. The maximum average output power was 130 mW. For Q-switched mode-locking operation, the repetition rate of the mode-locked pulses concentrated in the Q-switched envelope was 58 MHz. The repetition rate of the Q-switched envelope maintained at 18 kHz, while the pulse width decreased along with the increasing of pump power. The maximum average output power was 53 mW.     

Semiconductor type single wall carbon nanotube absorber for passive mode-locked Nd:YVO4 laser

The pure semiconductor type single wall carbon nanotubes (SWCNT) was transferred on hydrophilic glass substrate to fabricate saturable absorbers by vertical evaporation technique. The recovery time of the absorber is 350 fs. The saturation intensity of the absorber was found to be 115 μJ/cm² at 1060 nm. The modulation depth of the absorber could be about 7%. Passive mode-locked Nd:YVO₄ laser using this kind of absorber was demonstrated. The largest average output power of the mode-locked laser is 1.4 W at the pump power of 7.8 W. The continuous wave mode-locked pulses with the repetition of 80 MHz were achieved.     

Compact diode-directly-pumped passively mode-locked TEM<Subscript>00</Subscript> Nd:GdVO<Subscript>4</Subscript> laser at 1341 nm using a semiconductor saturable absorber mirror

We report on a compact 880-nm diode-directly-pumped passively mode-locked TEM₀₀ Nd:GdVO₄ laser at 1341 nm with a semiconductor saturable absorber mirror (SESAM) for the first time. Under the absorbed pump power of 14.6 W, the maximum output power of 1.27 W was obtained at the repetition rate of 85.3 MHz with the pulse width of 45.3 ps, corresponding to an optical-optical efficiency of 8.8% and the slope efficiency of 33.3%, respectively. The beam quality factor was measured to be M ² = 1.18, indicating a TEM₀₀ mode.     

Diode-pumped doubly Q-switched Nd:GdVO<Subscript>4</Subscript> laser

By using both an acoustooptical (AO) modulator and a Cr⁴⁺:YAG saturable absorber in the cavity, a diode-pumped doubly Q-switched Nd:GdVO₄ laser, which can generate short pulses with high peak powers and symmetric temporal profiles, has been demonstrated. A peak power of 3.05 kW with a corresponding pulse width of 16 ns has been achieved at an incident pump power of 7.7 W. A reasonable analysis about the experimental results has been given by considering the ground-state absorption and excited-state absorption of a Cr⁴⁺:YAG crystal.     

Diode-pumped passively Q-switched Nd:YVO<Subscript>4</Subscript> laser with a carbon nanotube saturable absorber

A diode end-pumped passively Q-switched Nd:YVO₄ laser with a transmission-type single-walled carbon nanotube saturable absorber is first demonstrated in this paper. The maximum continuous wave (CW) output power of 477 mW is obtained at the incident pump power of 1490 mW with the output transmission T = 10%, resulting in slope efficiency of 41.3%. For Q-switching operation, the measured pulse duration of 332 ns, the pulse energy of 326 nJ and the peak power of 982 mW are respectively obtained.     

High average power and short pulse duration continuous wave mode-locked Nd:GdVO<Subscript>4</Subscript> laser with a semiconductor absorber mirror

Passive mode locking of a solid-state Nd:GdVO₄ laser is demonstrated. The laser is mode locked by use of a semiconductor absorber mirror (SAM). A low Nd³⁺ doped Nd:GdVO₄ crystal is used to mitigate the thermal lens effect of the laser crystal at a high pump power. The maximum average output power is up to 6.5 W, and the pulse duration is as short as 6.2 ps. The optic-to-optic conversion efficiency is 32.5% and the repetition rate is about 110 MHz.     

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.     

Theoretical and experimental studies on the self-Q-switched and mode-locked Nd:GdVO<Subscript>4</Subscript>/KTP green laser

A diode-pumped self-Q-switched and mode-locked intracavity frequency doubled Nd:GdVO₄/KTP green laser is presented. The self mode-locking is self-starting and stable. About 100% modulation depth for the self-mode-locked green pulses has been achieved. We propose a developed rate equation model for self-Q-switched and mode-locked lasers, using the hyperbolic secant function methods and the theory of Kerr-lens mode-locking. This will consider the cascading of second-order nonlinearities of KTP crystal, the third-order nonlinearity of the laser medium, influences of the continuous pump rate, and the stimulated radiation lifetime of the active medium. With the model developed, theoretical calculations are shown to be in good agreement with experimental results. The width of the mode-locked green pulse is estimated to be about 120 ps. PACS 42.60.Fc; 42.60.Gd; 42.65.Hw     

High power ultrafast Nd:YVO<Subscript>4</Subscript> laser mode locked by single wall carbon nanotube absorber

We use a single walled carbon nanotubes (SWCNTs) absorber to demonstrate a high power mode locking for Nd:YVO₄ lasers. Under the pump power of 12 W, continuous wave mode-locked (CWML) pulse were generated with the maximum average output power of 3.6 W and the pulse duration of 7.6 ps. The peak power and the single pulse energy of the mode-locked laser were up to 4.9 kW and 37.5 nJ, respectively. To our knowledge, this is the highest average output power of the CWML laser with the SWCNTs absorber reported.     

Analysis of a laser-diode end-pumped intracavity frequency-doubled passively Q-switched and mode-locked Nd:GdVO<Subscript>4</Subscript>/KTP laser with a semiconductor saturable absorber

A diode-pumped passively Q-switched mode-locked (QML) intracavity frequency-doubled Nd:GdVO₄/KTP green laser with a semiconductor saturable absorber is presented. Nearly 100% modulation depth for the mode-locked green pulses can be achieved at any pump power over 1.92 W. The width of the mode-locked green pulse was estimated to be about 150 ps. The mode-locked pulse interval within the Q-switched envelope of 320 ns and the repetition rate of 97.5 kHz were obtained, at an incident pump power of 4.4 W. The repetition rate of the mode-locked green pulses inside the Q-switched envelope was 140 MHz.     

Diode-pumped simultaneously Q-switched and mode-locked Nd:GdVO<Subscript>4</Subscript>/LBO red Laser

A diode-end-pumped simultaneously Q-switched and mode-locked intracavity frequency doubled Nd:GdVO₄/LBO red laser with an acousto-optic Q-switch was realized. The maximum red laser output power of 250 mW was obtained at the incident pump power of 8.3 W and the repetition rate of 10 kHz. At 5 kHz, the maximum mode-locking modulation depth of about 80% was achieved with the Q-switched pulse width of 440 ns. The red mode-locked pulse inside the Q-switched pulse had a repetition rate of 115 MHz, its average pulse width was estimated to be about 350 ps.     

Diode single-end-pumped AO Q-switched Nd:GdVO<Subscript>4</Subscript> 266 nm laser

By simple extra-cavity frequency conversion, the performance of a diode single-end-pumped AO Q-switched Nd:GdVO₄/KTP/BBO 266 nm laser was demonstrated. Under the incident pump power of 14.32 W, the maximum average output power at 266 nm was 374 mW at the repetition of 20 kHz; the opticaloptical conversion efficiency was 2.6%. The corresponding pulse width was 5 ns, with the single-pulse energy and peak power calculated to be 18.7 μJ and 3.74 kW, respectively. The dependence of the operational parameters on the pump power was also investigated experimentally.     

Passively Q-switched GdVO<Subscript>4</Subscript>/Nd:GdVO<Subscript>4</Subscript> laser with Cr<Superscript>4+</Superscript>:YAG saturable absorber under direct 879 nm diode pumping to the emitting level

A passively Q-switched 1.06 μm laser with Cr⁴⁺:YAG saturable absorber by direct 879 nm diode pumping grown-together composite GdVO₄/Nd:GdVO₄ crystal to the emitting level was demonstrated in this paper. The characteristics of pulsed laser were investigated by using two kinds of Cr⁴⁺:YAG crystal with the initial transmissivity of 80 and 90%, respectively. When the T ₀ = 90% Cr⁴⁺:YAG was used, an average output power of 1.59 W was achieved at an incident pump power of 10 W. The pulse width and repetition rate were 64.5 ns and 170 kHz, respectively. The thermal lens effect of laser crystal was analyzed.     

Analytical and experimental studies on the diode-pumped,simultaneously Q-switched and mode-locked c-cut Nd:GdVO<Subscript> 4</Subscript>/KTP green laser with LT-GaAs absorber

A diode-pumped passively Q-switched mode-locked (QML) intracavity frequency doubled c-cut Nd:GdVO₄/KTP green laser with a LT-GaAs saturable absorber is presented. More than 90% modulation depth for the mode-locked green pulses has been achieved. Using the hyperbolic secant function methods, a developed rate equation model for Q-switched and mode-locked lasers considering the Gaussian spatial distribution of the intracavity photon intensity, the influences of continuous pump rate, the upper state lifetime of the active medium, and the excited-state lifetime of the saturable absorber, was proposed. With this developed model, the theoretical results are in good agreement with the experimental results and the width of the mode-locked green pulse was estimated to be about 380 ps.