YAG Saturable Absorber Research Articles

Output Characteristics of a Passively Q-Switched 946-nm Nd:YAG Laser with a Cr$^{4+}$:YAG Saturable Absorber

Output Characteristics of a Passively Q-Switched 946-nm Nd:YAG Laser with a Cr$^{4+}$:YAG Saturable Absorber

The characteristics of passively Q-switched and mode-locked 1.06 μm Nd:GdVO 4 laser with V:YAG saturable absorber

With V 3+:YAG as saturable absorber, the simple and highly efficient 1.06 μm Q-switched and mode-locked (QML) Nd:GdVO 4 laser is realized. The dependence of the output power, envelop repetition rate, and pulse width on the pump power, output coupler transmission, or cut direction of Nd:GdVO 4 (a-cut or c-cut) are investigated. Employing a-cut Nd:GdVO 4 and the output coupler with transmission of 27%, the maximum average output power of 3.57 W with a slope efficiency of 46% is obtained.

Modeling the Time-Dynamics of Miniature Passively $Q$-switched Lasers

The pulse-buildup in miniature passively <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</i> -switched lasers occurs in a similar time-scale as the phonon-assisted thermalization of the laser manifolds. We study how the time-dynamics of the laser is affected by the thermalization and relaxation processes using a dimensionless geometrical rate equation model for a homogeneously broadened four-level gain medium. The pulse length is found to depend strongly on the thermalization rate when the ratio of the ground-state absorption cross section of the saturable absorber to the spectroscopic emission cross section of the laser transition is small (lsim 10). Numerically calculated design curves are shown for the 1064 nm transition in Nd:YAG, and guidelines are given for applying the model to other transitions. Experimental results are used for estimating the thermalization time constant of Nd:YAG for the 1 mum transition group and the ground-state absorption cross section of the Cr <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4+</sup> :YAG saturable absorber crystal.

Optical triggering of a Q-switched Nd:YAG laser via transverse bleaching of a Cr:YAG saturable absorber

Optical triggering via direct bleaching of a Cr:YAG saturable absorber was applied to a monolithic Nd:YAG/Cr:YAG laser crystal. The method uses a single laser diode bar to bleach a thin sheet within the saturable absorber from a direction orthogonal to the lasing axis. By placing the Q-switch at the time corresponding to the steepest slope (dT/dt) for change in transmission during bleaching, the pulse-to-pulse timing jitter showed a 13.2x reduction in standard deviation, from 132 ns for free-running operation to 10 ns with optical triggering. We measured that a fluence of 60 kW/cm(2) was sufficient to enable optical triggering, where a diode appropriately sized for the length of the Cr:YAG (approximately 3 mm) would then require only approximately 150 W of optical power over a 1-2 micros duration to enable effective jitter reduction. Additionally, we measured an increase in optical-to-optical efficiency with optical triggering, where the efficiency improved from 12% to 13.5%.

High-temperature operation of a diode-pumped passively Q-switched Nd:YAG/Cr4+:YAG laser

The output performances of a diode-pumped Nd:YAG laser passively Q-switched by Cr4+:YAG saturable absorber crystal were investigated function of temperature. Increase of the temperature from 25 to 150°C increased slightly the laser pulse energy, and did not change the pulse duration. Furthermore, an increased absorbed energy of the pump radiation was necessary at temperatures higher than 25°C in order to maintain Q-switch operation. Measurements concluded that Cr4+:YAG transmission did not vary when temperature increased to 150°C. The decrease of Nd:YAG emission cross section with temperature and the changes of resonator configuration due to thermal effects were considered as main reasons for this behavior. The results of this work are valuable for designing a laser-ignition system for industrial gas engine or automotive industry.

Q-switched Nd lasers pumped directly into the 4F 3/2 emitting level

The influence of the direct pumping into the 4F 3/2 emitting level on the output characteristics of continuous-wave (CW) pumped, passively or actively (acoustooptic, AO) Q-switched Nd lasers is discussed. In case of passive Q-switching by Cr 4+:YAG saturable absorber (SA) crystal, the change of pumping wavelength from 0.81 μm into the highly-absorbing 4F 5/2 level to 0.88 μm into the 4F 3/2 level of Nd does not modify the energy of the Q-switch pulse, but increases the pulse repetition rate and the laser average power for the same absorbed pump power. This is demonstrated with 0.81 and 0.88 μm CW laser diode-pumped Nd:YAG and Nd-vanadate lasers with average output power in the watt-level range at 1.06 μm. The effect is explained by the control of passive Q-switching by the intracavity photon flux that is influenced by the pump wavelength and by the initial transmission of the SA crystal. On the other hand, it is discussed and experimentally proved that due to the possibility to control externally the frequency of switching, in case of the AO Q-switched Nd laser the change of the pump wavelength from 0.81 to 0.88 μm increases the pulse energy for a fixed frequency, leading to a corresponding increase of the average laser power.

Diode-Pumped Quasi-Three-Level Passively Q-Switched Nd:GGG Laser with a Codoped Nd,Cr:YAG Saturable Absorber

We demonstrate the first quasi-three-level passively Q-switched Nd:GGG laser at 937 nm using a Nd,Cr:YAG crystal as the saturable absorber. The dependences of the average output power, the repetition rate and the pulse width on the incident pump power are obtained. A maximum average output power of 1.18 W with repetition rate of 35 kHz and pulse width of 45 ns is achieved at an incident pump power of 18.3 W. The corresponding optical-to-optical and slope efficiencies are 6% and 10%, respectively.

Passively Q-switched yellow laser formed by a self-Raman composite Nd:YVO4/YVO4 crystal

Passively Q-switched yellow output from a frequency-doubled self-stimulating Raman composite Nd:YVO4/YVO4 laser using a Cr:YAG saturable absorber is reported. Maximum yellow output power of 264 mW was obtained with corresponding diode to yellow conversion efficiency of 5.9%.

LD-pumped 1.34 μm-Q-switched and mode-locked Nd:GdVO4 laser by a V3+:YAG saturable absorber

A diode-pumped passively Q-switched and mode-locked Nd:GdVO4 laser at 1.34 μm with V3+:YAG as the saturable absorber is realized in a V-type folded cavity. About 100% modulation depth of mode locking can be obtained as long as the pump power reaches the oscillation threshold. The width of the mode-locked pulse is estimated to be less than 280 ps with 200 MHz repetition rate within an about 980 ns-long Q-switched pulse envelope. A maximum output power of 200 mW and Q-switched pulse energy of 5.7 μJ is obtained.

Laser-diode-pumped doubly Q-switched Nd:GdVO4/KTA intracavity optical parametric oscillator

By using an acousto-optic (AO) modulator and a Cr4+:YAG saturable absorber, a high repetition rate doubly Q-switched noncritically phase-matched KTiOAsO4 (KTA) intracavity optical parametric oscillator (IOPO) at 1.50 μm is realized. In comparison to AO Q-switched IOPO, the lower threshold energy, the higher output average power, the narrower pulse width and the higher peak power from the doubly Q-switched IOPO can be obtained.

Pulse compression in an electro-optic Q-switched diode-pumped YVO_4/Nd:YVO_4 laser with a Cr^4+:YAG saturable absorber

A diode end-pumped doubly Q-switched YVO4/Nd:YVO4 laser has been realized for the first time to our knowledge by using both an electro-optic (EO) modulator and a Cr4):YAG saturable absorber. A 3.8 ns pulse width is generated by this laser under a pump power of 15 W at 2 kHz, which is obviously compressed in comparison with that of 8.8 ns from a single actively EO Q-switched laser. Under the same conditions, peak power values of 174.7 and 93 kW are also obtained. A coupled equation is given to theoretically analyze the experimental data. The experimental and theoretical results show that the doubly Q-switched laser has the advantages of a shorter pulse width and higher pulse peak power in contrast with a singly Q-switched laser.

Analysis of a laser-diode end-pumped passively Q-switched Nd:GdVO4 laser with V3+:YAG saturable absorber

By considering both the transversal and longitudinal Gaussian spatial distribution of the intracavity photon density, a couple of rate equations describing a laser-diode end-pumped passively Q-switched Nd:GdVO4 laser with V3+:YAG saturable absorber have been proposed. Solving these space-dependent rate equations numerically, we obtain the dependences of pulse width, pulse repetition rate, single-pulse energy and peak power on pump power. In the experiment, a laser-diode end-pumped Nd:GdVO4 laser passively Q-switched by a V3+:YAG saturable absorber has been realized, and the experimental results are consistent with the theoretical calculations.

Diode-pumped doubly Q-switched YVO4/Nd:YVO4 laser with BBO electric-optic Q-switch and Cr4+:YAG saturable absorber

In the experiment, we have demonstrated the performance of a laser-diode, end-pumped, doubly Q-switched YVO4/Nd:YVO4 laser with both a BBO electric-optic (EO) Q-switch and Cr4+:YAG saturable absorber. At a maximum incident pump power of 15 W and an EO Q-switch repetition rate of 8 kHz, the stable laser pulses with the pulse duration 5.28 ns, the single pulse energy 0.14 mJ, and the pulse peak power 26 kW are obtained. The experimental results show that the double Q-switched laser with EO and Cr4+:YAG can generate the shorter pulse and the higher peak power in comparison to singly Q-switched laser with EO.

Reduction of timing jitter in a Q-Switched Nd:YAG laser by direct bleaching of a Cr4+:YAG saturable absorber

A method for optical triggering of a Q-switched Nd:YAG laser by direct bleaching of a Cr:YAG saturable absorber is described. This method involves the bleaching of a thin sheet of the saturable absorber from a direction orthogonal to the lasing axis using a single laser diode bar, where the Cr:YAG transmission increased from a non-bleached value of 47% to a bleached value of 63%. For steady state operation of a passively Q-switched laser (PRF=10 Hz), the pulse-to-pulse timing jitter showed approximately 12X reduction in standard deviation, from 241 nsec for free running operation to 20 nsec with optical triggering.

Diode-pumped passively Q-switched Nd:GdVO4 laser at 1342 nm with V:YAG saturable absorber

We have demonstrated an efficient diode-pumped passively Q-switched Nd:GdVO4 laser working at 1342nm by using an uncoated V3+:YAG crystal as the saturable absorber, in which both a-cut and c-cut Nd:GdVO4 crystals are employed. At the maximum absorbed pump power of 9.45W, the maximum average output power can reach 519mW and 441mW corresponding to the output coupler with different transmission of 3% and 10% by using an a-cut Nd:GdVO4 crystal at 1342nm, while the shortest pulse duration could be as low as 21.7ns and 22.3ns with the repetition rate of 48.41kHz and 53.25kHz by using a c-cut Nd:GdVO4 crystal, corresponding to the output coupler with different transmission of 3% and 10% at 1342nm, and the single Q-switched pulse energy are 6.67uJ and 7.06uJ, the pulse peak power are 307W and 316W, respectively. The experimental results show that c-cut Nd:GdVO4 laser can generate shorter pulse with higher peak power in comparison with a-cut one.

Diode end-pumped passively Q-switched Nd:YAG ceramic laser with Cr4+:YAG saturable absorber

We report on a diode end-pumped passively Q-switched Nd:YAG ceramic laser. By using a Cr4+:YAG single crystal with an 80% initial transmission as the saturable absorber, stable Q-switched pulses with a 126-μJ pulse energy, a 12-ns pulse width, and an 8.4-kHz pulse repetition rate have been obtained. The Q-switching performance of the laser under different saturable absorption strengths and output couplings was experimentally investigated.

Diode-pumped passively Q-switched and modelocked Nd:GdVO_4 laser at 134 μm with V:YAG saturable absorber

Using V:YAG as the saturable absorber, a diode-pumped passively Q-switched and mode-locked Nd:GdVO(4) laser at 1.34 microm is realized. Nearly 100% modulation depth of mode-locking has been achieved. The width of the mode-locked pulse is estimated to be less than 460 ps with 125 MHz repetition rate within an about 1 micros-long Q-switched pulse envelope. A maximum output power of 220 mW and Q-switched pulse energy of 10.5 microJ is obtained. Using the hyperbolic secant function methods, a fluctuation rate equation model considering the Gaussian distribution of the intracavity photon density and the population inversion in the gain medium as well as the ground-state population intensity of the saturable absorber has been proposed to describe the mode-locking process of diode-pumped Nd:GdVO(4)/V(3+):YAG laser. With the space-dependent rate equations solved numerically, the theoretical calculations reproduce the laser characteristics well.

&gt;1 MW peak power single-mode high-brightness passively Q-switched Nd^3+:YAG microchip laser

A high-brightness diode end-pumped Nd:YAG microchip laser, passively Q-switched by a Cr(4+):YAG saturable absorber (SA), has been developed. The dependences of pulse energy and width were investigated based on theoretical verification to enhance the peak power. As a result, the peak power exceeded 1.2 MW with M(2) = 1.04 and spectrum width Delta lambda < 5.1 pm at a repetition rate of 100 Hz. Brightness of 98 TW/sr x cm(2) was obtained with a supplied average electrical power of 2.3 W. The peak power increased up to 2.1 MW with M(2) = 1.36. Peak power of 1.7 MW was obtained from a 2-cm-diameter x 5-cm-long monolithic laser head.

Intracavity optical parametric oscillator pumped by passively Q-switched Nd:YLF laser

AbstractWe report on a passively Q-switched end pumped Nd:YLF laser including a noncritically phase-matched KTP singly resonant intracavity optical parametric oscillator (IOPO-KTP). For the Q-switching operation we have used Cr:YAG saturable absorber. The optimized passively Q-switched Nd:YLF laser without IOPO generated linearly polarized pulses of 11.5 ns and 1.07 mJ at 1047 nm. The conversion efficiency of the optimized Q-switched pulse energy at 1047 nm to 1547 nm of a signal approached about 47%. For optimizing both Nd:YLF laser and IOPO we have numerically solved a theoretical model. We have achieved 1.6-ns duration pulses at 1547 nm with energy of 0.5 mJ and peak power of above 300 kW. The beam quality was excellent (M2 ≈1).

LD-pumped passively Q-switched Nd:YVO4/YVO4 laser with an Nd3+:Cr4+:YAG saturable absorber

By using a piece of codoped Nd3+:Cr4+:YAG crystal as a saturable absorber, a laser-diode pumped passively Q-switched Nd:YVO4/YVO4 laser has been realized. The maximum laser output power of 2.452 W has been obtained at the incident pump power of 8.9 W for an 8.8% transmission of the output coupler at 1064 nm, corresponding to a slope efficiency of 30%. The other output laser characteristics of the laser have also been investigated. The laser with a Nd3+:Cr4+:YAG saturable absorber has a lower threshold pump power and a higher slope efficiency compared to that with a similar small-signal transmission of a Cr4+:YAG saturable absorber.