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Comparison between c-cut and A-cut Nd : YVO4 lasers passively Q-switched with a Cr4+: YAG saturable absorber
Abstract
Comparison between c-cut and a-cut Nd:YVO4 microchip lasers passively Q-switched with a Cr4+:YAG saturable absorber is experimentally made. The lower emission cross section of the c-cut Nd:YVO4 crystal can enhance the passive Q-switching effect to produce a peak power 10 times higher than that obtained with the a-cut
crystal. The experimental result further reveals that a c-cut Nd:YVO4 crystal is a very convenient material for short-pulse (sub-nanosecond) and high-peak-power (>10kW) lasers.
... 18,19 However, there's a slight difference in the fundamental wavelength between a-cut and c-cut Nd:YVO 4 crystals. 20 The fundamental wavelength of c-cut Nd:YVO 4 locates at 1066 nm, and the SHG of its Raman laser emits at 589 nm. Duan 24 The study of passively Q-switched Raman laser is beneficial to the development of miniaturized, low-fabrication cost and reliable laser source, and has significant values for laser applications. ...
... 28,29 The c-cut Nd:YVO 4 owns smaller cross section at 1066 nm with comparing to a-cut counterpart, which also has advantages in Q-switch operation for achieving narrow pulse width and high energy. 20,30 Both the Cr 4+ : YAG and Nd:YVO 4 were composited with its pure crystals to enhance the heat dissipation capability. A 3 Â 3 Â 2 mm 3 Cr 4+ :YAG crystal was diffusion bonded with an undoped 3 Â 3 Â 3 mm 3 YAG crystal with an initial transmittance of 85%. ...
Compact 589 nm yellow source was reported and generated from intracavity frequency‐doubling of c‐cut YVO4/Nd:YVO4/YVO4 Raman laser. A Cr4+:YAG/YAG composite was adopted for compact passively Q‐switching operation. Double‐end composited Nd:YVO4 crystal was designed to reduce the thermal effect and increase Raman crystal length. Both noncritical phase‐matching (NCPM) LBO crystal and critical phase‐matching (CPM) BBO crystal were used as frequency doubling crystal for comparison. 780 mW output power of 589 nm yellow emission was achieved with an incident pump power of 16 W. The pulse repetition frequency and pulse width were 41 kHz and 3.6 ns at the maximum output power, respectively. The results show passively Q‐switched operation provides a compact method to obtain 589 nm yellow emission.
... Another approach to reducing σ em in a Nd:YVO 4 crystal could be switching to a c-cut crystal, where σ em is 0.65 × 10 −18 cm 2 , which is comparable to a Nd:YAG crystal. In this case the energy output reached is 18 µJ with a peak power of 21.2 kW [19]. ...
... By inserting these values into Eqs. (19)(20)(21)(22)(23) we can obtain the Eq. (6) in the main section. ...
We present a giant-pulse generation laser realized by the emission cross-section control of a gain medium in a passively Q-switched Nd:YVO4 microchip laser with a Cr⁴⁺:YAG saturable absorber. Up to 1.17 MW peak power and 1.03 mJ pulse energy were obtained with a 100 Hz repetition rate. By combining the Nd:YVO4 crystal with a Sapphire plate, lower temperature difference between a pump region in the gain crystal and a crystal holder was obtained which helped to keep the cavity in stability zone at elevated temperatures and allowed the achievement of the high peak power for this laser system.
... Q-switched laser is one of the most important techniques of the solid-state laser due to its extremely high peak power pulsed output in comparison with the continuous wave (CW) laser [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. Passively Q-switched (PQS) lasers, in particularly, have benefits of low cost and simple design that are more attractive in applications without the requirement of accurate repetition rate [1][2][3][4][5][6]. ...
... Q-switched laser is one of the most important techniques of the solid-state laser due to its extremely high peak power pulsed output in comparison with the continuous wave (CW) laser [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. Passively Q-switched (PQS) lasers, in particularly, have benefits of low cost and simple design that are more attractive in applications without the requirement of accurate repetition rate [1][2][3][4][5][6]. Nowadays, the use of solid-state saturable absorber, like utilizing the Cr 4+ :YAG crystal, to replace the traditional dyes makes the PQS laser more reliable. ...
An energy adjustable passively Q-switched laser is demonstrated with a composite Nd:YAG/Cr⁴⁺:YAG crystal by applying a wedged interface inside the crystal. The theoretical model of the monolithic laser resonator is explored to show the energy adjustable feature with different initial transmissions of the saturable absorber at the horizontal axis. By adjusting the pump beam location across the Nd:YAG crystal, the output pulse energy can be flexibly changed from 10.9 μJ to 17.6 μJ while maintaining the same output efficiency. The polarization state of the laser output is found to be along with the polarization of the C-mount pump diode. Finally, the behavior of the multi-transverse-mode oscillation is also discussed for eliminating the instability of the pulse train.
... It is specially noted that the Nd:YVO 4 crystal used in our experiment is impressively cut along c-axis, not along a-cut. Normally, the effective stimulated emission cross-section of a-cut Nd:YVO 4 is four-times larger than that of a c-cut Nd:YVO 4 [46], [47]. A larger stimulated emission cross-section generally means a lower pump threshold for continuous-wave (CW) operation, but this may be disadvantageous for pulsing operation, especially for passively Q-switched lasers. ...
... In an a-cut Nd:YVO 4 crystal, the strongest emission generally occurs at 1064 nm for the transition of 4 F 3/2 → 4 I 11/2 , whereas a c-cut Nd:YVO 4 crystal has a relatively complex emission spectrum for the 4 F 3/2 → 4 I 11/2 transition. The emission cross sec- tions at series wavelengths in the 4 F 3/2 → 4 I 11/2 transition are comparable to each other and any of these spectrums can emit under the particular conditions [46], [49], which the observed dual-wavelength spectrum in our experiment is also included. ...
We demonstrate for the first time, to the best of our knowledge, a dual-wavelength nanosecond-pulsed Nd:YVO4 laser passively Q-switched by a topological-insulator (TI) Bi2Se3 saturable absorber (SA). The few-layer Bi2Se3 nanosheets are fabricated by the liquid-phase exfoliation technique, and are then coated on the output mirror of a diode-pumped c-cut Nd:YVO4 laser. The synchronized Q-switching operation at 1066.6 and 1066.8 nm is successfully achieved. The Q-switched repetition rate is tunable in a wide range of 1-135 kHz, and the maximum pulse energy is obtained to be 0.56 μJ (corresponding to the peak power of 1.87 W). The obtained pulse width can be as narrow as 250 ns, which is the shortest one from the reported TI-based Q-switched lasers.
... Nd:YVO 4 lasers are characterized by their high gain and high lasing efficiency. Passive Q-switching of the Nd:YVO 4 lasers was demonstrated using many different groups of saturable absorbers such as GaAs wafers [Li et al., 2001], Cr 4+ :YAG crystals [Chen et al., 2002] and SESAM [Fluck et al., 1997]. The Nd 3+ -ions have a large stimulated emission cross-section and short lifetime in the upper state when doped in the YVO 4 host, passively Q-switched pulses obtained in the laser normally have higher repetition rate and lower pulse energy than those obtained in the Nd 3+ -doped YAG laser, whereas, Nd:GdVO 4 crystal is a newly developed laser gain medium. ...
... Under the optimal CW operation condition we then inserted the saturable absorber in the laser cavity. It was believed that a large ratio between the laser beam sizes in the gain medium and in the saturable absorber is favorable for achieving a good passive Q-switching [Chen et al., 2002]. Therefore, Cr 4+ :YAG saturable absorber was put close to the flat output coupler where the laser beam has the smallest size after considering the thermal lens effect in gain medium. ...
We report on the experimental observation of dynamic behaviors in diode pumped passively Q-switched Nd:GdVO4 and Nd:YVO4 lasers. In addition to the period-doubling route to chaos, various periodic windows have also been observed. Based on an extended rate equation model the chaotic nature of the lasers is numerically simulated. It was found that under the experimental condition the model could qualitatively reproduce the experimental observations.
... With the absorbed pump power increased from 0.60 W to 2.50 W, the pulse width of the Nd:YAG SCF laser decreases drastically. This rapid decreasing trend also consistent with the typical phenomena that pulse width varies with the incident pump power [31,32]. The gradual increase of the pump power makes the inversion particles in the low Q-value state accumulate in the upper energy level of the gain medium. ...
A promising Nd:YAG single-crystal fiber (SCF) was successfully fabricated by the laser-heated pedestal growth method. The compact passively Q-switched laser has been realized for the first time with a 794 nm laser diode pumping. Pulsed laser performances of this SCF were investigated in detail with a flat-flat resonator. Under the absorbed pump power of 2.50 W, the peak power of 274.24 W was obtained with 19.41 ns pulse duration width and 65.94 kHz repetition rate.
... As well know, we used a-cut Nd:YVO4 (4 × 4 × 20 mm, 0.2 % doping) because it has a maximum output power 7 times higher than c-cut. 12 To keep the Nd:YVO4 temperature constant, an amount including a cooling system was designed. An acousto optical (AO) Qswitch was used to make a pulse beam. ...
... This forms the basic SHG intracavity structure used in the experiments. For the simulation inputs, some values that could not be easily measured via experiment such as the absorption and stimulated emission cross sections were taken from the reported papers [15][16][17][18][19][20]. The inputs to the simulation are listed in Table 1. ...
In this paper, a novel approach to modelling intracavity second harmonic generation (SHG) in periodically poled MgO-doped lithium niobate (PPLN) is presented and verified against experimental results. This approach involves combining the coupled nonlinear wave equations with a rate equation model for a diode-pumped solid-state Nd:YVO4 laser, taking into account both the depletion of the fundamental wave due to the energy conversion from the fundamental wave to the SHG wave and the reduction of the fundamental wave within a laser cavity due to the loss as a result of the SHG nonlinear process. It was shown that the theoretical simulation matched the experimental results well, while also providing physical insight into the importance of the fundamental wave depletion in the intracavity SHG nonlinear processes. The resulting model is computationally simple and has the potential to generalize to the other nonlinear processes such as three-wave mixing and optical parametric oscillation.
... In order to attain the heat dissipation as soon as possible and effectively cooling the temperature of two laser crystals, they were directly mounted in a copper stove full of cooled water. Though the thermal conductivity and mechanical hardness of the Nd:YVO 4 crystal were both lower than that of the Nd:YAG crystal, we still employed the Nd:YVO 4 material as the MOPA laser crystals because of its intrinsic advantages including large stimulated emission cross section and natural birefringence [20]. Moreover, because the Nd:YVO 4 crystal material of the master oscillator was identical to that of the MOPA, it was easy to realize the gain match between the master oscillator and MOPA and therefore achieve an efficient power amplification [21]. ...
We presented a 125 W single-frequency continuous-wave (CW) 1064 nm laser, where a homemade 50.3 W single-frequency CW high quality Nd:YVO 4 laser and a two-stage dual-end-pumped master-oscillator power amplifier (MOPA) acted as the seed source and amplifier, respectively. As a result, a maximum output power of 125.2 W was achieved with the incident pump power of 200 W. The optical-to-optical conversion efficiency and the overall amplified power gain were 43.3% and 3.28%, respectively. The measured beam quality M ² and the long-term power stability of the 1064 nm amplifier during 8 h were better than 1.28 and ±0.73%, respectively. Additionally, the power extraction efficiency of the designed MOPA system was further investigated and the results revealed that the key of improvement of the power extraction efficiency of the MOPA system was employing a high-power single-frequency CW laser as the master oscillator.
... Its stimulated-emission cross section parallel to the c axis (σ == 25 × 10 −19 cm 2 ) is about four times higher than that orthogonal to the c axis (σ ⊥ 6.5 × 10 −19 cm 2 ). However, the large stimulated emission cross section is not suitable for PQS lasers due to the limitation of energy storage capacities [6,17,25]. Therefore, a c-cut Nd:YVO 4 crystal with a smaller stimulated-emission cross section is more appropriate for PQS self-Raman laser operation. Due to the relatively poor thermal and mechanical characteristics of Nd:YVO 4 crystal, the PQS self-Raman performance is hindered by the thermal loading of the combined laser/Raman process, which will limit Raman laser output power and beam quality. ...
An in-band pumped passively -switched (PQS) self-Raman laser with a c-cut composite crystal is demonstrated for the first time to our knowledge. A composite crystal was utilized to improve the stability and misalignment sensitivity of the resonator. The PQS self-Raman output performance was systematically investigated with different initial transmissions ( ) of the and different transmissions ( ) of the Raman output coupler. In addition, the focus position of the incident pump beam and cavity length have been optimized during the experiment. With of and output coupler of , the maximum average output power at 1178 nm was up to 2.53 W under the absorbed pump power of 20.6 W, corresponding to an optical-to-optical conversion efficiency of 12.3%. The pulse repetition frequency and pulse width were measured to be 39.1 kHz and 20.4 ns, respectively, and the corresponding pulse energy and peak power were calculated to be 64.7 μJ and 3.2 kW. At the full output power, the fluctuation of Raman output power was less than within one hour. To the best of our knowledge, we have improved the PQS self-Raman laser about 3.2 times.
... In our Q-switching experiments, the gain media, the radii of the input mirrors and output mirrors, the transmittance of the mirrors, and the initial transmissions of SA for different wavelengths are all different, which causes the different stabilities of the three lasers. Compared with the 1.064 and 1.991 μm lasers, the smaller laser mode radius on the SA, larger reflectivity of the output mirror, and higher absorbance of SA in the visible laser are conducive to the result that the pulse train of the visible Q-switched laser is more uniform than those of the other two [53]. With the relationship between intracavity power and the output power, the intracavity energy intensity I on the SA can be calculated by the following formula: ...
Rhenium disulfide (ReS2), a member of group VII transition metal dichalcogenides (TMDs), has attracted increasing attention because of its unique distorted 1T structure and electronic and optical properties, which are much different from those of group VI TMDs (MoS2, WS2, MoSe2, WSe2, etc.). It has been proved that bulk ReS2 behaves as a stack of electronically and vibrationally decoupled monolayers, which offers remarkable possibilities to prepare a monolayer ReS2 facilely and offers a novel platform to study photonic properties of TMDs. However, due to the large and layer-independent bandgap, the nonlinear optical properties of ReS2 from the visible to mid-infrared spectral range have not yet been investigated. Here, the band structure of ReS2 with the introduction of defects is simulated by the ab initio method, and the results indicate that the bandgap can be reduced from 1.38 to 0.54 eV with the introduction of defects in a suitable range. In the experiment, using a bulk ReS2 with suitable defects as the raw material, a few-layered broadband ReS2 saturable absorber (SA) is prepared by the liquid phase exfoliation method. Using the as-prepared ReS2 SA, passively Q-switched solid-state lasers at wavelengths of 0.64, 1.064, and 1.991 μm are investigated systematically. Moreover, with cavity design, a femtosecond passively mode-locked laser at 1.06 μm is successfully realized based on the as-prepared ReS2 SA for the first time. The results present a promising alternative for a rare broadband optical modulator and indicate the potential of ReS2 in generating Q-switched and mode-locked pulsed lasers. It is further anticipated that this work may be helpful for the design of 2D optoelectronic devices with variable bandgaps.
... Nd:YVO 4 as a tetragonal zircon structure laser crystal has polarized absorption and radiation characteristics. For the fundamental laser emission around 1.06 μm, its stimulatedemission cross section of the a-cut crystal (25×10 −19 cm 2 ) is about four times larger than that of the c-cut crystal (6.5×10 −19 cm 2 ) [17]. The c-cut Nd:YVO 4 crystal with a smaller stimulated-emission cross section usually results in a shorter pulse width and higher peak power in Q-switch operation. ...
A cascaded c-cut Nd:YVO4 crystal self-Raman operation was demonstrated with a Raman shift of 259 cm⁻¹. The Stokes oscillation with a primary Raman shift of 890 cm⁻¹ was suppressed and a cascaded self-Raman with a single Raman shift of 259 cm⁻¹ was realized based on suitable coating design. At an incident pump power of 13.3 W, the second Stokes at 1129 nm was obtained as the main output laser and the output power was about 0.81 W. As the incident pump power increased, dual Stokes at 1129 and 1163 nm were obtained. A maximum output power of up to 1.0 W with a conversion efficiency of 6.7% was achieved at an incident pump power of 14.9 W and a pulse repetition frequency of 15 kHz.
... For the LIPI method, one of the major difficulties for actual applications, especially for some small engines such as automobiles is the size of the laser head due to the fact that the laser head should be inserted into the engines. It is well-known that passively Q-switched lasers have advantageous of simple fabrication, compact structure, and low cost [8][9][10]. Therefore, this kind of laser is the most promising candidate for the LIPI system. ...
A novel four-beam (named laserI, laser II, laser III and laser IV, respectively), passively Q-switched, pulse-burst ceramic Nd:YAG laser under 2 × 2 micro-lens array pumping was demonstrated for the purpose of laser-induced plasma ignition (LIPI). Multiple-beam output together with pulse-burst mode in which both high repetition rate and high pulse energy can be realized simultaneously were obtained to greatly improve the performance of LIPI. The pulse-burst contained a maximum of 5 pulses, 3 pulses, 2 pulses and 3 pulses for laserI, laser II, laser III and laser IV, respectively, and the corresponding repetition rate of laser pulses in pulse-burst was 10.8 kHz, 7.2 kHz, 6.8 kHz and 5.2 kHz, respectively. The output energy for single laser pulse in pulse-burst was in the range of 0.12 mJ to 0.22 mJ.
... For the laser-induced plasma ignition, a lot of efforts have done to reduce the size of the laser head because in many actual applications a small size of laser is required. It is wellknown that passively Q-switched lasers have become more and more important for its unique characteristics, such as simple fabrication, compact structure, and low cost [6][7][8][9][10]. Hence, this type of laser is the most promising candidate for the laser-induced plasma ignition. ...
A novel miniaturized Cr⁴⁺:YAG passively Q-switched Nd:YAG pulse-burst laser under 808 nm diode-laser pulse-pumping was demonstrated for the purpose of laser-induced plasma ignition, in which pulse-burst mode can realize both high repetition rate and high pulse energy simultaneously in a short period. Side-pumping configuration and two different types of laser cavities were employed. The pumping pulse width was constant at 250 μs. For the plane-plane cavity, the output beam profile was flat-top Gaussian and the measured M² value was 4.1 at the maximum incident pump energy of 600 mJ. The pulse-burst laser contained a maximum of 8 pulses, 7 pulses and 6 pulses for pulse-burst repetition rate of 10 Hz, 50 Hz and 100 Hz, respectively. The energy obtained was 15.5 mJ, 14.9 mJ and 13.9 mJ per pulse for pulse-burst repetition rate of 10 Hz, 50 Hz and 100 Hz, respectively. The maximum repetition rate of laser pulses in pulse-burst was 34.6 kHz for 8 pulses at the incident pump energy of 600 mJ and the single pulse width was 13.3 ns. The thermal lensing effect of Nd:YAG rod was investigated, and an plane-convex cavity was adopted to compensate the thermal lensing effect of Nd:YAG rod and improve the mode matching. For the plane-convex cavity, the output beam profile was quasi-Gaussian and the measured M² value was 2.2 at the incident pump energy of 600 mJ. The output energy was 10.6 mJ per pulse for pulse-burst repetition rate of 100 Hz. The maximum repetition rate of laser pulses in pulse-burst was 27.4 kHz for 6 pulses at the incident pump energy of 600 mJ and the single pulse width was 14.2 ns. The experimental results showed that this pulse-burst laser can produce high repetition rate (>20 kHz) and high pulse energy (>10 mJ) simultaneously in a short period for both two different cavities.
Saturable absorbers (SAs) based on novel two-dimensional (2D) materials have gained significant attention for their favorable processing characteristics, desirable structures, and excellent nonlinear optical properties, particularly in solid-state laser pulse...
To reach the second threshold criterion for the Nd:YVO 4 passively Q-switched laser with a Cr ⁴⁺ :YAG saturable absorber, the method of temperature-elevating for decreasing emission cross section with a proper gain-medium-to-absorber-mode-size-ratio resonator is explored.
We report a diode-pumped solid-state (DPSS) laser used for intracavity pump-enhanced difference frequency generation (DFG) to create a 3.5-micron laser. Using a 50 mm-long periodically poled lithium niobate (PPLN) crystal inside the cavity of an Nd:YVO4 solid-state laser at 1064 nm with 4.5 W pump power at 808 nm, and a 310 mW C-band signal at 1529 nm, up to 31 mW of mid-infrared output power at 3499 nm is obtained. The cavity requires no active stabilization and/or locking, and the entire cavity is <8 cm in length. The obtained output power corresponds to a black-box efficiency of 2.20%W⁻¹, which is the highest value reported to date for continuous-wave DFG based on a bulk nonlinear optical crystal with no active stabilization. Potential future applications in free-space optical communication are also discussed.
We report a diode pumped solid state (DPSS) laser used for intracavity pump-enhanced difference frequency generation (DFG) to create a 3.5 micron laser. Using a 50 mm-long periodically poled lithium niobate (PPLN) crystal inside the cavity of an Nd:YVO4 solid state laser at 1064 nm with 4.5 W pump power at 808 nm, and a 310 mW C-band signal at 1529 nm, up to 31 mW of mid-infrared output power at 3499 nm is obtained. The cavity requires no active stabilization and/or locking, and the entire cavity is <8 cm in length. The obtained output power corresponds to a black box efficiency of 2.20 %W-1, which is the highest value reported to date for continuous wave DFG based on a bulk nonlinear optical crystal with no active stabilization. Potential future applications in free space optical communication are discussed as well.
In this work, the relationship between local structures and the photoluminescence parameters of neodymium activated fluorite crystals has been preliminary investigated in CaF2 crystals. The first principles calculation results reveal that as the size of codoped rare earth ions become smaller, the corresponding stable clusters twists progressively from cubic sublattice to square antiprism. The regulated spectral line properties and the concentration dependent photoluminescence parameters, including the absorption, emission and decays, agree well with the calculated results. In detail, the cubic stable clusters of Nd³⁺,La³⁺:CaF2 and Nd³⁺,Gd³⁺:CaF2 crystals possess similar spectral characteristics, while the other category of Nd³⁺,Y³⁺:CaF2 and Nd³⁺,Lu³⁺:CaF2 resembles both in the square antiprism cluster structures and spectra. Besides, a crystal with ultra long lifetime near 600 µs, wide emission bandwidth and high thermal conductivity has been obtained, which is promising for generation of the LD-pumped ultrafast lasers. By connecting the enriched spectral properties with local structures, it is highly expected to design new laser materials through regulating the local structures of active ions in rare earth doped fluorite crystals.
We report the design and operation of two self-Raman lasers optimized for emission at 1216 nm and 608 nm, utilizing a combination of Raman shifts at 890 and 259 cm⁻¹ in c-cut Nd:YVO4 crystal. Key to the efficient operation of these lasers was the use of a double-end diffusion-bonded Nd:YVO4 composite crystal. This enabled the generation of a maximum average output power of 2.6 W at 1216 nm (with a diode-Stokes conversion efficiency of 14.7%) from the Stokes-optimized cavity. With the incorporation of a non-critically phase matched LBO crystal and a slight cavity re-design, the Stokes field at 1216 nm was frequency doubled to the orange part of the visible spectrum (608 nm), where a maximum average output power of 1.71 W was achieved with a diode-orange conversion efficiency of 9.7%.
In the paper, passively mode-locked laser of c-cut Nd:La0.05Lu0.95VO4 crystal at 1.08 and 1.06μm were firstly demonstrated with a semiconductor saturable absorber mirror (SESAM). A simple and flexible method of selecting the mode-locking wavelength using a pair of prisms and a blade was applied. In 1.08μm band, two mode-locked laser states oscillating at 1084.8 nm and 1087.9 nm were obtained, respectively. In 1.06μm band, dual-wavelength mode-locking at 1065.3 nm and 1067.5 nm was achieved. Current results indicate that c-cut Nd:La0.05Lu0.95VO4 crystal could be a potential gain medium for helium optical pumping, as well as generation of terahertz (THz) radiations.
A sub-nanosecond microchip laser was constructed using a Nd:La0.15Gd0.85VO4 with Cr⁴⁺:YAG saturable absorber. A single 880 ps pulse was recorded under an incident pump power of 4.91 W, corresponding to a repetition rate of 35 kHz. When the incident pump power exceeded 5 W, the system transferred a single picosecond pulse train into 0.9/1.1 ns two pulse train forms. The average output power increased from 108 mW to 130 mW, corresponding to a peak power decrease from 3.5 kW to ∼1.8 kW, which might be utilized for laser pulse self-calibrations in time-of-flight distance measurements.
A new neodymium-doped (Nd³⁺-doped) Ca0.7La0.3Al12O19 (Nd:CLA) disordered crystal was successfully grown by the Czochralski method. The performance of diode-pumped Nd:CLA (a-cut and c-cut) lasers was demonstrated for the first time. For the c-cut crystal continuous-wave (CW) operation, we obtained the highest output power of 2.08 W at the wavelength of 1053.2 nm, and the slope efficiency was 23% versus the incident pump power. By inserting a Cr⁴⁺:YAG absorber, we successfully achieved a passively Q-switched laser, and the shortest pulse width was 18.36 ns with a peak power of 364.6 W. Compared with a-cut crystal, c-cut crystal has superior laser characteristics.
In this work, a passively Q-switched Nd:YAG laser resonator, with an output coupling of more than 90%, was demonstrated. Laser pulse energy, peak power and pulse width were found to increase with the increasing of dissipative loss of the laser resonator, and pulse energy was found to increase from 38.6 mJ to 113 mJ, which almost meant a 200% increase. However, according to previous theoretical analyses of passively Q-switched lasers, pulse energy and peak power would decrease with the increasing of dissipative loss when the second threshold was satisfied, and a giant Q-switched laser pulse would never occur if the second threshold was not satisfied. For the passively Q-switched laser resonator we established, the second threshold was found not to be satisfied because of the high output coupling. So, we modified the solutions of coupled rate equations when the second threshold was not satisfied. Numerical calculation results were carried out, and these calculation results were basically consistent with the experimental results and previous investigations.
The fluorescence quenching caused by Nd3+ clusters in Nd3+ doped crystal even at low Nd3+ concentration has restrained the performance of Nd3+ laser. In this work, Nd3+:CaNb2O6 and Nd3+:La3+:CaNb2O6 single crystals have been grown by the Czochralski method. RE3+ (RE3+=Nd3+, La3+) ion incorporation mechanisms, the formation of Nd3+ clusters, and the feasibility of La3+ ions as buffers in RE3+:CaNb2O6 crystal have been demonstrated and assessed by atomistic simulation methods. The spectral and laser properties of the Nd3+:CaNb2O6 and Nd3+:La3+:CaNb2O6 have been measured. All the results indicate the Nd3+ dimers with distances between Nd3+ close to the critical interaction distance have formed in the Nd3+:CaNb2O6 and the La3+ ions as buffers can alleviate the interaction of Nd3+ effectively in the Nd3+:La3+:CaNb2O6 as expected. Benefitting from the introducing of La3+ buffers, about 2.6 W fundament laser with slope efficiency of 36.5% and about 310 mW self-stimulated Raman scattering laser with conversion and slope efficiencies of 8.3% and 9.5%, respectively, which are superior to those of the Nd3+:CaNb2O6, have been achieved in the Nd3+:La3+:CaNb2O6.
A diode pumped and passively Q-switched Nd:YVO4 laser was demonstrated to emit kW-peak-power pulse. This laser was compact, low-threshold and free of any active cooling. The emitted light pulse showed 6.9-ns duration, 3.3-kW peak power and 25.4-kHz repetition frequency at 3.5-W pump power. The laser output was stable and the laser beam had a near-diffraction-limited quality.
A diode-pumped continuous-wave (CW) and passively Q-switched Nd:LuLiF 4 laser was investigated. Under an incident pump power of 11.2 W, an output power of up to 1.92 W was generated, corresponding to a slope efficiency of 17.4%. By using a Cr ⁴⁺ :YAG wafer as saturable absorber, stable Q-switched pulse trains with an average output power of 1.13 W and a pulse duration of 13.8 ns were captured at a repetition rate of 32.5 kHz, delivering a pulse energy of 36.4 μJ. A rate equation model was further introduced to theoretically analyze the dynamical mechanism, in which the Gaussian spatial distribution theory was taken into account.
We report the fabrication and operation of a single-to-three-mode, sub-nanosecond passively Q-switched Nd:Lu0.61Gd0.39VO4/Cr⁴⁺:YAG microchip laser, which exhibits changes in mode structure with increasing incident pump power. The laser exhibits longitudinal mode oscillations with a partial transverse mode overlap. The shortest pulse duration, highest pulse energy and peak power observed are 646 ps, 8.7 μJ and 13.5 kW, respectively.
An admirable and efficient Nd:YVO4 laser at 1085 nm is demonstrated with a compact 35 mm plano-plano cavity. A chosen narrow bandpass filter with high-transmittance (HT) coating at 1064 nm (T=96%) and optimized part-reflection (PR) coating at 1085 nm (T=15%) is used as the output coupler. In the continuous-wave (CW) regime, the maximum output power reaches 3110 mW at the pump power of 11.41 W. Based on a Cr:YAG crystal with initial-transmittance of 91%, the first passively Q-switched Nd:YVO4 laser at 1085 nm is achieved. When the pump power is changed from the threshold of 4.50 to 6.08 W, the dual-wavelength lines at 1064 and 1085 nm are generated simultaneously. However, at the pump power of above 6.08 W, the single-wavelength line at 1085 nm is achieved. The largest output power, the highest peak power, and the narrowest pulse width are 1615 mW, 878 W and 26.2 ns, respectively. © 2017 Society of Photo-Optical Instrumentation Engineers (SPIE).
A passively Q-switched self-Raman laser emitting at 1178 nm is demonstrated with a c-cut Nd:YVO4 crystal, using a Cr:YAG crystal as a saturable absorber. At a pump power of 5.0 W the maximum average output power of 540 mW is obtained, corresponding to an optical-to-optical conversion efficiency of 10.8%. Pulse duration of 10.8 ns, pulse-repetition rate of 42.5 kHz, and energy per pulse of 12.7 μJ are achieved when the pump power is 5.0 W. Interestingly, the second-Stokes component at 1316 nm appears when the pump power reaches 4.0 W.
In this article, the report of design, construction and optimization of an xenon flash-lamp pumped solid-state Nd:YAG laser in a ceramic cavity is presented. A laser rod of Nd:YAG with a 1.1 wt% doping and a dimension of 80 mm×5 mm, as an active medium, and a xenon flash-lamp with a inner diameter of 7 mm, an arc length of 3 in, and a repetition frequency of 0.2 Hz, as the pump source, were used. At first, the laser was optimized with Findlay-Clay method, in terms of the output coupler reflectivity. The gain and the loss for pump energy of 4.9 J were achieved to be 0.9 and 0.005, respectively. Thus we calculated the optimum reflectivity as 32%. From a mirror with a reflectivity as 25% (which was the closest to our available reflectivity in laboratory) was used. A total electrical-to-optical efficiency of 3% was achieved at 1064 nm for 25% reflectivity for output coupler. For a 0.2 Hz repetition rate and a pumping energy of 9 J, a beam spot size of 3.98 and a quality factor of 17 were achieved. The results are valid for a cavity design with the mentioned parameters.
We demonstrated in an _a_-cut Nd:La0.25Gd0.75VO4 mixed crystal the passively mode locking laser of two different wavelengths in orthogonal polarization states with a semiconductor saturable absorber mirror (SESAM). Due to the special anisotropic gain feature of the mixed crystal, through careful controlling on the cavity loss anisotropy, the simultaneous orthogonal polarization states laser were also achieved. In σ polarization states, the pulse width of 2.2 ps was close to the shortest pulse width obtained with Nd-doped vanadate crystal to my knowledge. What's more, dual-wavelength synchronized mode locking and bound-soliton-like pulse mode locking was also experimentally observed.
Passively continuous-wave mode-locking (CWML) characteristics from a class of mixed Nd:Gdx
Y1−x
VO4 laser crystals at 1.34 μm have been investigated with a semiconductor saturable absorber mirror (SESAM) for the first time. In contrast to the single Nd:YVO4 and Nd:GdVO4 crystals, the mixed vanadate crystals can produce broader emission spectra, shorter pulse width, and higher peak power. Under the same conditions, the mode-locking performances from series mixed vanadate crystals as well as the emitting spectral properties were experimentally investigated. At an incident diode pump power of 7.1 W, a minimum pulse width was as short as 6.3 ps from the mixed vanadate crystal with x = 0.63, while the highest peak power was 4.5 kW from the mixed crystal with x = 0.83.
We demonstrate a passively Q-switched c-cut Nd:YVO4 laser based on graphene-oxide (GO) as a saturable absorber (SA). The Q-switched laser has a low pump threshold of 1.5 W. The pulse repetition rate can be widely changed from 62 kHz to 386 kHz by increasing the pump power from 1.5 W to 3 W. The minimum pulse width is 246 ns and the maximum average output power is 514 mW.
A high repetition-rate, short-pulse Nd:YVO4 laser based on electro-optical cavity-dumped technology is reported. This laser, end-pumped by a continuous-wave 880 nm laser diode, employs a Pockels cell made up of BBO crystal as the electro-optical Q switch. The laser resonant cavity is optimized to improve its dynamically thermal stability and the mode-matching efficiency. When the pump power is 30 W, stable 1064 nm fundamental-mode laser pulses with the maximum repetition rate of 500 kHz, pulse width of 6 ns and average power of 10 W can be achieved.
In this letter, we discussed the theoretical requirements of resonator stability, and found that resonator with G1*G2*=1/2 or closer to it was deep stable and insensitive to the thermal lens of laser crystal. The resonator was designed according to the obtained theoretical results. Laser with optimized concavo-convex cavity was found to meet the condition of violent change of environment temperature and the variation of thermal lens of laser crystal by our experiments.
The goal of this chapter is to provide the fundamentals of solid-state lasers used in medical applications. After a brief introduction, the fundamental properties of solid-state laser active media are described. The main part of this chapter contains the description of a solid-state laser system, its pumping and cooling, modes of operation, and emission wavelength control, including a non-linear conversion of radiation. In the following part, a detailed description of selected solid-state laser types used in medical applications is given. At the end of this chapter, the construction and materials of some novel solid-state lasers are described.
We report subnanosecond passively Q-switched Nd:GdxY1−xVO4 (x = 0, 0.18, 0.42, 0.51, 0.64, 1) microchip lasers. To the best of our knowledge, this is the first demonstration of subnanosecond mixed-vanadate-crystal microchip lasers. Compared with Nd:GdVO4 and Nd:YVO4 lasers, we obtain enhanced peak power by the microchip lasers proposed and elaborated. Using a Cr4+:YAG crystal with initial transmission of 77%, we achieve the shortest pulse duration of 588 ps, highest pulse energy of 30 μJ, and peak power of 48 kW.
We explore synchronization dynamics of dual-polarization solid-state lasers. Such lasers are able to produce a stable beat frequency in a wide range from Hz up to THz. This work take advantage of it in order to study several frequency locking mecanisms in these lasers. First, we build a dual-polarization laser with a semiconductor saturable absorber miror (SESAM). It enable a pulsed operation of the laser where all longitudinal modes are phase-locked, and this on both laser eigenstates. We also demonstrate that polarization state of successive pulses forms sequences that we describes here. A particular phenomenon is observed in this laser: when the beat-frequency is chosen equal to half the free spectral range of the laser, then the two frequency combs associated with the two laser eigenstates synchronize themself. Second, we submit a two-frequency laser to a frequency-shifted feedback. Doing so, we are able to transfer the radiofrequency synthetizer stability on the laser beat-frequency. This result is obtained both in cw and Q-switched regimes. Finally, together with the frequency-shifted feedback, we use the relaxation oscillations of a class B laser to induce a regime where the laser beat-frequency is synchronized with the external reference, while their relative phase oscillates. Subsequently, particular intensity dynamics are observed at the output.
In a previous Letter [Opt. Lett. 40, 1177 (2015)OPLEDP0146-959210.1364/OL.40.001177], oscillation wavelengths corresponding to two σ-polarized transition lines and were described in inverse. Here, the corrected correspondence between transition lines and oscillation wavelengths is addressed.
Newman (J. Appl. Phys. 34:437, 1963) first presented the use of semiconductor sources to pump a solid-state laser. The technology of diode-pumped solid-state laser (DPL) is now mature after more than 40 years development. DPL has attracted much attention in broad applications, such as industry, medical and military fields, scientific research, etc., due to the advantages of high efficiency, compact configuration, long lifetime, high reliability, and good beam quality. In this chapter, we firstly present a historical overview of DPL for four stages. Then, the principle DPL and related thermal effect will be introduced. Based on the theoretical analysis, different kind of DPL devices have been developed. Finally, the THz-wave generation using DPL technology also will be presented.
The passively Q-switched Yb:NaY(WO4)2 (Yb:NaYW) laser is studied. By using Cr4+:YAG as the saturable absorber, a very stable pulse train is obtained. At a high pump power, the pulse to pulse timing jitter is measured to be less than 2% and the amplitude fluctuation is less than 4%. A Q-switched average output power of 2.3 W at 1029 nm is generated with a slope efficiency of 33.9%; the one-dimensional intensity distribution of the laser facula is of the Gaussian type. The output repetition rate, pulse energy, pulse width and peak power are 33.3 kHz, 70 μJ, 36 ns and 2.0 kW, respectively. The passively Q-switched process is simulated by solving the rate equations, the simulated results are in good agreement with the experimental data.
Owing to the small differences between the cross-sections of the four emission peaks around 1.3 μm, an efficient four-wavelength synchronous launched laser is demonstrated using a Nd:GdLuAG crystal. The laser has no special resonator design. The maximum output power is 4.28 W, which corresponds to a conversion efficiency of 45.6%. For the Q-switching, the laser operated in dual-wavelength mode, and the single pulse energy is maintained at ~80 μJ. By calculating the population inversion density, multi-wavelength emission characteristics in both continuous wave and Q-switching lasers are discussed.
A diode pumped doubly passively Q-switched Yb: NaY(WO4)(2)/Cr4+:YAG / GaAs laser was realized for the first time to our knowledge. Compared with the singly passively Q-switched Yb:NaY(WO4)(2)/Cr4+:YAG laser, this laser can generate a higher repetition rate, and more symmetric and shorter pulses. The highest repetition rate and shortest pulse width was measured to be 82 kHz and 6 ns. At certain pump power, 1022 and 1026 nm dual-wavelength lasers were obtained, and the mechanism of this phenomenon was discussed.
Spontaneous formation of coherent vector fields, which results from synchronization of longitudinal modes of orthogonally polarized transverse modes, has been observed in a laser-diode (LD)-pumped thin-slice c-cut laser with reflective end faces operating under the multi-longitudinal mode oscillation condition. The suppression of antiphase dynamics inherent to multimode solid-state lasers as well as the enhanced self-mixing interference effect as compared with a linearly polarized multimode laser have been identified.
A side-pumped passively Q-switched 1064 nm laser system by using Nd: YAG/Cr4+: YAG/YAG composite crystal is demonstrated for the first time. Under pump power of 180 W, the maximum average output power of 85.6 W is obtained, with the pulse width of 140 ns and the repetition rate of 14.3 kHz, corresponding single pulse energy of 6.0 mJ and peak power of 42.7 kW. To our knowledge, this is the maximum average power of 1064 nm passively Q-switched laser which has reported.
Sub-nanosecond passively Q-switched microchip lasers based on Nd:YVO4 and Cr4+:YAG were reported. On the whole, 2 at.% doped Nd:YVO4 crystals exhibited better performance than 3 at.% doped crystals. The shortest pulse duration of 693 ps was obtained from a-cut, 2 at.% doped Nd:YVO4, and the highest peak power of 32 kW, largest pulse energy of 29 μJ were produced by c-cut, 2 at.% doped sample. These experiment results illustrate that Nd:YVO4 and Cr4+:YAG are good combination for producing sub-nanosecond, high peak power microchip lasers.
We passively Q switched a Nd:LaSc3(BO3)4 microchip laser with an antiresonant Fabry–Perot saturable absorber (A-FPSA) and achieved single-frequency, 180-ps pulses with 0.1 μJ of pulse energy at a repetition rate of 110 kHz. Because of the compactness and scaling possibilities offered by the A-FPSA, the pulse width can be varied from 180 ps to 30 ns and the repetition rate from 50 kHz to 7 MHz.
Passively Q-switched 1.064-μm microchip lasers have been constructed from thin pieces of Nd³⁺:YAG bonded to thin pieces of Cr⁴⁺:YAG. When pumped with the unfocused 1.2-W output of a fiber-coupled diode, these devices produced 11-μJ pulses of 337-ps duration at a pulse repetition rate of 6 kHz in a single-frequency TEM00 mode. The peak power of the lasers was in excess of 28 kW, with unfocused peak output intensities exceeding 180 MW/cm².
A diode-pumped Nd:YAG laser is passively Q switched by using F2⁻ color centers in lithium fluoride as a saturable absorber. When cw pumped with a laser diode, the laser produces pulses of 20–30-nsec duration at 1064 nm, with an energy of as much as 20 μJ and a peak power of more than 1 kW. Data are presented on pulse width, energy, and repetition rate as a function of pump power. When the laser is operated at high pulse energy levels, a gradual bleaching of the saturable absorber is observed.
We demonstrate, for the first time as far as we know, a passively Q-switched operation of a Nd:YVO4 laser in which a Cr⁴⁺:YAG crystal and a laser-diode bar are used as the saturable absorber and the pump source, respectively. Stable laser pulses as short as 28 ns with 20-µJ energy can be generated with this laser, which has the advantages of simplicity, high efficiency, and good long-term stability.
The conventional rate equations for a Q-switched laser are
augmented to explicitly include the effects of time- and level-dependent
pumping, thermalization among the sublevels in the upper and lower
multiplets, and multiplet relaxation in a homogeneously broadened
four-level laser medium. To make the numerical computations more
generally valid, we introduce a number of dimensionless variables. We
show that the initial set of five coupled differential equations can be
reduced to a simple set of two coupled equations for the inversion
density and photon flux. Via numerical modeling, we have investigated
the manner in which both thermalization and lower multiplet relaxation
affect Nd:YAG laser characteristics such as output energy and temporal
waveform. Our numerical results confirm earlier predictions that the
Q-switched Nd:YAG laser output energy increases monotonically by a
factor of 3.33 as one progresses from the assumption of slow to rapid
thermalization and by an additional factor of 1.46 if one further
assumes a terminal multiplet relaxation which is fast relative to the
resonator photon decay time. We also find that the laser pulsewidth is
substantially broadened when the resonator photon decay time is
comparable to the thermalization, and to a lesser extent, the terminal
multiplet relaxation times
Summary form only given. Passively Q-switched microlasers are an elegant means to generate sub-nanosecond duration pulses with moderate energies. Earlier work on these devices has emphasized that the following criterion must be met to ensure Q-switching: σgs /γσ×As/Ag>1, where, σgs, is the saturable absorber ground-state absorption cross section, σ is the gain medium emission cross section, γ is the gain medium degeneracy factor, and Ag and A s are the laser beam areas in the gain medium and saturable absorber, respectively. We assembled and characterized a CW pumped Nd:YVO4/Cr:YAG microlaser
With a 10-W diode laser to pump Nd:GdVO4 crystal in a folded cavity, we demonstrated Cr4+:YAG passively Q-switched Nd:GdVO4 lasers at 1.06μm. The maximum average output power of 2.1W and the highest peak power of 625W were, respectively, obtained
when the initial transmissions of the Cr4+:YAG crystals were 90% and 80%.