Adjustable picosecond pulse duration in a LD end pumped SESAM passively mode-locked Nd:YVO<Subscript>4</Subscript> laser

With adjustable pulse durations, a semiconductor saturable absorber mirror (SESAM) passively mode-locked picosecond Nd:YVO₄ laser was studied. The pulse duration was adjustable from 20 to 80 ps by using intracavity etalons of different thicknesses.     

Theoretical analysis and experimental research on thermal focal length of a YVO4/Nd:YVO4 composite crystal

This paper investigates the temperature field distribution and thermal focal length within a laser diode array (LDA) end-pumped YVO4/Nd:YVO4 rectangular composite crystal. A general expression of the temperature field distribution within the Nd:YVO4 rectangular crystal was obtained by analysing the characteristics of the Nd:YVO4 crystal and solving the Poisson equation with boundary conditions. The temperature field distributions in the Nd:YVO4 rectangular crystal for the YVO4/Nd:YVO4 composite crystal and the Nd:YVO4 single crystal are researched respec- tively. Calculating the thermal focal length within the Nd:YVO4 rectangular crystal was done by an analysis of the additional optical path differences (OPD) caused by heat, which was very identical with experimental results in this paper. Research results show that the maximum relative temperature on the rear face of the Nd:YVO4 crystal in the composite crystal is 150 K and the thermal focal length is 35.7 mm when the output power of the LDA is 22 W. In the same circumstances, the experimental value of the thermal focal length is 37.4 mm. So the relative error between the theoretical analysis and the experimental result is only 4.5%. With the same conditions, the thermal focal length of the Nd:YVO4 single crystal is 18.5 mm. So the relative rate of the thermal focal length between the YVO4/Nd:YVO4 crystal and the Nd:YVO4 crystal is 93%. So, the thermal stability of the output power and the beam quality of the YVO4/Nd:YVO4 laser is more advantageous than the laser with Nd:YVO4 single crystal.     

Simultaneous dual-wavelength laser operation at 1342 and 946 nm in two laser crystals and their sum-frequency mixing

A sum-frequency yellow-green laser at 554.9 nm is reported by this paper, 946 nm wavelength is obtained from ⁴F_3/2-⁴I_9/2 transition in Nd:YAG and 1342 nm wavelength is obtained from ⁴F_3/2-⁴I_13/2 transition in Nd:YVO₄. Using a doubly folded-cavity type-II critical phase matching KTP crystal intra cavity to make 946 nm laser from Nd:YAG and 1342 nm laser from Nd:YVO₄ frequency summed, with incident pumped power of 30 W in Nd:YAG and 20 W in Nd:YVO₄, TEM₀₀ mode yellow-green laser at 554.9 nm at 1.15 W is obtained and its M² factor is less than 1.22. The experimental results show that the Nd:YAG and Nd:YVO₄ crystals intra-cavity sum-frequency mixing is an effective method for yellow-green laser and it can be applied to other two laser crystals to obtain more all-solid-state lasers with different wavelengths.     

All-solid-state CW doubly resonant sum-frequency mixing red-orange laser at 611 nm

We report for the first time a continuous wave (CW) coherent radiation at 611 nm by intracavity sum-frequency generation of 1064 nm Nd:YVO₄ laser and 1433 nm Nd:YAP laser. Red-orange laser is obtained by using a doubly cavity, type-II critical phase matching KTP crystal sum-frequency mixing. With total pump power of 27.9 W (17.8 W pump power for 1433 nm Nd:YAP laser and 10.1 W pump power for 1064 nm Nd:YVO₄ laser), TEM₀₀ mode red-orange laser at 611 nm of 1.15 W is obtained. The red-orange power stability in 30 min is better than 4.3%.     

Comparison between c-cut and a-cut Nd:YVO4 lasers passively Q-switched with a Cr4+:YAG saturable absorber

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 (>10 kW) lasers. Received:10December2001/Revisedversion:22January2002 / Published online: 14 March 2002     

Laser performance of grown-together YVO4/Nd:YVO4 composite crystal at continuous-wave 914 nm

We demonstrated a diode-end-pumped continuous-wave 914 nm laser using a novel grown-together YVO₄/Nd:YVO₄ crystal for the first time. A maximum output power at 914 nm of 7.5 W with an optical-optical efficiency of 16.3% and a slope efficiency of 24.3% was obtained when the incident pump power was 46.2 W. The beam quality factor M ² was 3.2 at the output power of 6.0 W. The quality and specification of the grown-together composite YVO₄/Nd:YVO₄ crystal should be improved. Meanwhile, energy-transfer upconversion spectrum of the composite YVO₄/Nd:YVO₄ crystal laser was also investigated.     

Efficient continuous-wave YVO<Subscript>4</Subscript>/Nd:YVO<Subscript>4</Subscript> Raman laser at 1176 nm

We present a simple and compact continuous-wave (CW) 1176 nm laser based on self-frequency Raman conversion in continuous-grown YVO₄/Nd:YVO₄ composite crystal. With a composite crystal 30 mm in length, a maximum output power up to 1.84 W was achieved at the incident diode pump power of 23.6 W. Corresponding to overall optical conversion, the efficiency was 7.8% and the slope efficiency was 8.5%. The conversion efficiency has been doubled compared with the conventional Nd:YVO₄ CW self-frequency Raman laser. The excellent performance of this laser shows that the long continuous-grown YVO₄/Nd:YVO₄ composite crystal is promising in the application of CW Raman lasers and ideal for miniaturization.     

An Intracavity-Triggered Passively-Switched Nd:YVO<Subscript>4</Subscript> Laser

We demonstrate an intracavity-triggered passively Q-switched Nd:YVO₄ laser within a diode-end-pumped configuration. We employ a Cr⁴⁺:YAG saturable absorber as the passive Q switch and an Nd:LiYF₄ (YLF) laser as the laser triggering of the Q-switched laser. Since we use the same Cr⁴⁺:YAG crystal and output coupler with the Nd:YVO₄ laser, the Cr⁴⁺:YAG Q switch is triggered inside the Nd:YLF laser cavity. As a result, the timing jitter in standard deviation of Nd:YVO₄ laser can be reduced to 16 ns.     

All-solid-state doubly resonant intracavity frequency sum mixing orange yellow laser with 3.2 W output power at 593.5 nm

A compact and efficient 593.5 nm orange-yellow laser is realized using doubly resonant intracavity sum frequency mixing. Two Nd: YVO₄ crystals are employed as the gain crystals. In two sub-cavities, 1064 nm radiation from one Nd: YVO₄ and 1342 nm radiation from the other Nd: YVO₄ are mixed to generate 593.5 nm orange-yellow laser. In the overlapping of the two cavities, sum frequency mixing is achieved in a type I critical phase matching (CPM) LBO crystal. An output power of 3.2 W at the wavelength of 593.5 nm is obtained with total incident pump power of 38 W. The optical to optical conversion efficiency is up to 8.4% and the stability of the output power is better than 2.48% in 8 h. To the best knowledge, this it the highest watt-level laser at 593.5 nm generated by diode end pump all-solid-state technology.     

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.     

37 W 888-nm-pumped grown-together composite crystal YVO<Subscript>4</Subscript>/Nd:YVO<Subscript>4</Subscript>/YVO<Subscript>4</Subscript> oscillator at 1342 nm

We report on a continuous-wave Nd:YVO₄ oscillator at 1342 nm based on the combination of a grown-together composite crystal YVO₄/Nd:YVO₄/YVO₄ and the 888 nm diode-laser direct pumping for the first time. At the absorbed pump power of 102 W, a maximum average output power of 37.2 W at 1342 nm was obtained, corresponding to an optical-optical conversion efficiency of 36.5% and a high slope efficiency of 63.0%, respectively. To the best of our knowledge, this is the highest output power ever obtained for a 1342 nm Nd:YVO₄ oscillator.     

Experimental observation of chaotic phase synchronization of a periodically pump-modulated multimode microchip Nd:YVO4 laser

In this Letter we demonstrate the experimental observation of chaotic phase synchronization (CPS) in a periodically pump-modulated multimode microchip Nd:YVO₄ laser. PS transition is displayed via the stroboscopic technique. We apply the recurrence probability and correlation probability of recurrence to estimate the degree of PS. The degree of PS is studied taking into account the modulation amplitude and modulation frequency. We also propose an experimental compatible numerical simulation to reflect the fact that the Arnold tongues are experimentally and numerically exhibited in the periodically pump-modulated multimode microchip Nd:YVO₄ laser.     

Optical properties and laser performance of neodymium doped scheelites CaWO4 and NaGd(WO4)2

Nd-doped CaWO₄ (CWO) and NaGd(WO₄)₂ (NGWO) single crystals with good optical quality have been grown by the Czochralski technique. The neodymium distribution coefficient in these matrices is about 0.4 for CWO and close to unity for NGWO. Polarized absorption and emission spectra have been recorded at room temperature and used to calculate the absorption and stimulated emission cross-sections.1 and 2% Nd : CWO and 1 % Nd:NGWO laser rods have been tested in a cavity longitudinaly pumped by an 1 W AIGaAs laser diode and compared to Nd : YAG and Nd:YVO₄ rods in the same conditions. The 2% Nd: CWO rod exhibits the best performance with slope efficiencies of 64%, higher than in the case of YAG and equal to the YVO₄ samples. The dependence of the laser output power versus the diode temperature has been measured for all these materials. The laser output of Nd: CWO was found to be nearly as stable as for Nd : YVO₄ and much more stable than in the case of Nd : YAG. A CWO microchip has also been tested for the first time to our knowledge.     

LD泵浦Nd:YVO_4双波长运转腔内和频491nm激光器

分析了Nd:YVO4激光器实现双波长运转及腔内和频的条件,利用一种LD泵浦Nd:YVO4晶体产生1 064 nm和914 nm双波长激光束,采用一个线性平凹腔结构,利用腔内Ⅰ类临界相位匹配LBO和频,获得了连续波输出的全固态激光器。实验采用端面结构,在5.0 W的808 nm泵浦功率下,获得了最高功率为2.5 mW连续波TEM00的激光输出,光-光转换效率为0.05%。     

The thermal effect in diode-end-pumped continuous-wave 914-nm Nd:YVO4 laser

The thermal effect and the heat generation in diode-end-pumped continuous-wave 914-nm Nd:YVO₄ lasers are investigated in detail. A theoretical model of a diode end-pumped solid-state laser is constructed to analyse the influence of fractional thermal loading on the thermal effect in the Nd:YVO₄ laser based on finite element analysis. The thermal focal lengths and the end-surface deformations of laser rods in Nd:YVO₄ quasi-three-level and four-level lasers are measured and compared with the results obtained by ordinary interferometry for the demonstration of higher thermal loading in 914-nm laser. Finally the fractional thermal loading in the Nd:YVO₄ quasi-three-level laser is calculated by matching the experimental and the simulated end deformations.     

Influence of the laser-diode temperature on crystal absorption and output power in an end-pumped Nd:YVO<Subscript>4</Subscript> laser

In this work, we studied the influence of heat loaded into the laser crystal in an end-pumped solid-state Nd:YVO₄ high power laser. We have shown experimentally that the optimum value of the laser-diode temperature for the maximum pump power absorption by the Nd:YVO₄ crystal and the maximum Nd:YVO₄ laser output power are approximately similar to that of a system of the low power type, but by increasing the pump power, different values can be obtained.     

Diode-pumped Nd:YVO<Subscript>4</Subscript>/Nd:YLF laser at 488 nm

We present a laser architecture to obtain continuous-wave blue radiation at 488 nm. A 808 nm diode-pumped the Nd:YVO₄ crystal emitting at 914 nm. A part of the pump power was then absorbed by the Nd:YVO₄ crystal. The remaining was used to pump the Nd:YLiF₄ (Nd:YLF) crystal emitting at 1047 nm. Intracavity sum-frequency mixing at 914 and 1047 nm was then realized in a BiB₃O₆ (BiBO) crystal to reach the blue radiation. We obtained a continuous-wave output power of 339 mW at 488 nm with a pump laser diode emitting 18.3 W at 808 nm.     

激光二极管端面抽运的1.34μm Nd:YVO4平凹腔型激光器

理论上分析了端面抽运的1.34μm Nd:YVO₄平凹腔型激光器的各项参数；实验 上实现了LD端面抽运的1.34μm Nd:YVO₄平凹腔型激光器的运转. 关键词： 固体激光 4晶体')" href="#">Nd:YVO₄晶体 平凹腔     

Diode-pumped Nd:LuVO<Subscript>4</Subscript>-Nd:YVO<Subscript>4</Subscript> laser at 492 nm with intracavity sum-frequency-mixing in LiB<Subscript>3</Subscript>O<Subscript>6</Subscript>

We present for the first time a Nd:YVO₄ laser emitting at 1064 nm intracavity pumped by a 916 nm diode-pumped Nd:LuVO₄ laser. A 809 nm laser diode is used to pump the Nd:LuVO₄ crystal emitting at 916 nm, a Nd:YVO₄ laser crystal was pumped at 916 nm and lased at 1064 nm. Intracavity sum-frequency mixing at 916 and 1064 nm was then realized in a LiB₃O₆ (LBO) crystal to reach the blue range. We obtained a continuous-wave output power of 216 mW at 492 nm under 19.6 W of incident pump power at 809 nm.     

Laser-diode end-pumped intracavity frequency doubling semiconductor saturable absorber mirror passively mode-locked picosecond lasers

A diode pumped Nd:YVO₄ semiconductor saturable absorber mirror (SESAM) passive mode-locked intracavity frequency doubled laser was studied. A type II phase matching KTiOPO₄(KTP) crystal and a type I phase matching LiB₃O₅ (LBO) frequency doubling crystal were respectively inserted in the cavity. With a pump power of 4.5 W, a 90 mW output of frequency doubled beam and 29.7 ps pulse duration were achieved with frequency doubled by KTP. With the same pump power a 140 mW output of frequency doubled beam and 3.67 ps pulse duration were achieved with LBO.