High power diode single-end-pumped Nd:YVO4 laser

A fiber-coupled diode-single-end-pumped Nd:YVO₄ laser with an Nd:YVO₄ crystal of 0.3 at% doping concentration and 3×3×10 mm³ dimensions was reported. 14.850 W of continuous-wave output power in an M² factor of 1.12 was obtained under pump power of 27.365 W, with an optical conversion efficiency of 60.49%, and a slope efficiency of 64.5%.     

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.     

A comprehensive study of Nd:YAG, Nd:YAlO3, Nd:YVO4 and Nd:YGdVO4 lasers operating at wavelengths of 0.9 and 1.3 μm. Part 1: cw-operation

This paper reports on efficient generation of cw laser radiation at 0.9 and 1.3 μm in different neodymium doped laser hosts. The thermal, mechanical and optical properties as well as the laser performance of Nd:YAG, Nd:YAlO₃, Nd:YVO₄ and Nd:GdVO₄ are studied in numerical simulations as well as in experimental investigations. For example an output power of more than 4.0 W is generated in Nd:YVO₄ at the 914 nm ⁴F_3/2→⁴I_9/2 transition using a pump power of 19 W. In Nd:GdVO₄ more than 6.0 W are obtained at the 1342 nm ⁴F_3/2→⁴I_13/2 laser transition by using a pump power of 19.3 W. The spatial beam quality of both lasers is diffraction limited with an M² value of less than 1.1. PACS  42.70.Hj; 42.55.Xi; 42.60.Pk     

Power scale-up of the diode-pumped actively Q-switched Nd:YVO4 Raman laser with an undoped YVO4 crystal as a Raman shifter

With an undoped YVO₄ crystal as a Raman shifter, we substantially improved the reliability and the output performance of an actively Q-switched 1176-nm Nd:YVO₄ Raman laser. With an incident pump power of 18.7 W, the average power is greater than 2.6 W at 80 kHz. The pulse width of the pulse envelope is shorter then 5 ns with mode-locked modulation. With an incident pump power of 12.7 W, the pulse energy and peak power is higher than 43 μJ and 14 kW at 40 kHz. PACS 42.55.Ye; 42.55.Xi; 42.60.Gd     

Diode-pumped continuous-wave Nd:YVO<Subscript>4</Subscript> laser with self-frequency Raman conversion

Continuous-wave operation of a diode-pumped Nd:YVO₄ laser with self-frequency Raman conversion is demonstrated. The threshold of Raman generation was measured to be 1.3 W of laser diode power. The maximum output power of Stokes radiation at the wavelength of 1177 nm was up to 50 mW at a laser diode pump power of 2.3 W, corresponding to the slope efficiency of 5%. The beam quality M² of the Stokes radiation was about 1.4. The fluctuations of the Stokes power were minimised down to 4%. PACS 42.55.Ye; 42.60.Pk; 42.65.Dr     

Co2+:LMA crystal as saturable absorber for a diode-pumped passively Q-switched Nd:YVO4 laser at 1342 nm

We have demonstrated an efficient diode-pumped passively Q-switched Nd:YVO₄ laser at 1342 nm by using an uncoated Co²⁺:LaMgAl₁₁O₁₉ (Co²⁺:LMA) crystal as the saturable absorber. With the absorbed pump power of 11.7 W, the pulse width could be as low as 42 ns, with a corresponding average output power of 580 mW. At around 40 kHz repetition rate, the energy of a single Q-switched pulse was estimated to be about 14.5 μJ and the peak power was 346 W. The passive Q switching operation for the Co²⁺:LMA in different polarization states was also investigated. PACS 42.55.-f; 42.55.Xi; 42.60.Gd; 42.70.Mp     

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

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

High-power high-repetition-rate acousto-optically Q-switched 1342 nm laser

A high-power high-repetition-rate acousto-optically Q-switched 1342 nm laser with double Nd:YVO₄ crystals pumped by fiber-coupled laser diodes is presented. The highest output power of 13.7 W was achieved with a total of 42 W pumping power in cw operation, the slope efficiency was measured as 36%, and the optical efficiency was better than 32%. In Q-switchedoperation, the highest pulse repetition rate of 100 kHz was obtained. At 50 kHz repetition rate, the laser exported 11.2 W average output power, with 60 ns average pulse width, ∼5% width stability (RMS) and ∼8% peak-power stability (RMS). At 10 kHz repetition rate, the highest average output power was measured as 6.3 W, single pulse energy was calculated as 0.63 mJ, with pulse width of 19 ns and peak-power higher than 30 kW. Combining the experimental results, we analyze and discuss some problems concerning Nd:YVO₄ crystal working at 1,342 nm wavelength. PACS 42.55.-f; 42.55.Xi; 42.60.Gd     

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.     

Efficient diode-pumped Nd:YVO4 continuous-wave laser at 1.34 μm

We report a high-power continuous-wave(cw) diode-pumped efficient 1.34 μm Nd:YVO₄ laser. The laser properties of a low Nd³⁺-doped concentration of the Nd:YVO₄ crystal operating at 1.34 μm formed with a simple plane-concave cavity have been demonstrated. With the incident pump power of 22 W, an output power of 8.24 W was obtained, giving an optical conversion efficiency of 37.5% and slope efficiency of 40%. The thermal effects of cw end-pumped solid-state lasers were studied.     

Radially polarized laser beam from a Nd:YAG laser cavity with a c-cut YVO4 crystal

We demonstrate the generation of a radially polarized beam by simply inserting an undoped c-cut YVO₄ crystal into a Nd:YAG laser cavity. In a hemispherical cavity, the cylindrically symmetric, positive birefringence of the YVO₄ crystal extends the stability limit of the cavity length for an extraordinary ray (radial polarization) compared to an ordinary one (azimuthal polarization). By adjusting the cavity length, a radially polarized beam with an output power up to 1 W was selectively obtained. In addition, a higher-order transverse mode was also generated by arranging the cavity design. The method demonstrated in this paper can be readily applied to laser systems with an isotropic laser medium. PACS 42.60.Da; 42.25.Lc; 42.25.Ja     

Dual-wavelength laser operation at 1064 and 914 nm in two Nd:YVO<Subscript>4</Subscript> crystals

We present for the first time a dual-wavelength laser operation at 1064 and 914 nm in two NdYVO₄ crystals. A 879 nm laser diode is used to pump the first Nd:YVO₄ crystal emitting at 914 nm, and the second Nd:YVO₄ laser emitting at 1064 nm intracavity pumped at 914 nm. A total output power of 4.28 W at the two fundamental wavelengths was achieved at the absorbed pump power of 13.8 W. The M² values for 914 and 1064 nm lights at the maximum output power were found to be around 1.3 and 1.1, respectively.     

Diodes-double-end-pumped high efficiency continuous wave 36 W TEM00 mode Nd:GdVO4 laser

A effective continuous-wave (CW), high power laser generated using a YVO₄/Nd:YVO₄ composite crystal is presented. 18.8 W output power in multi-mode has been achieved with a maximum absorbed pump power of 31.2 W, corresponding to an optical-to-optical efficiency of 60.26%. In TEM₀₀ mode operation, 15.1 W output power also has been achieved with the maximum absorbed pump power of 31.2 W, corresponding to an optical-to-optical efficiency of 47.69%. With a 200 mm focal-length positive lens and using the moving knife-edge method, the beam quality factor is measured to be M² = 1.2 for TEM₀₀ mode beam.     

A 15.1 W continuous wave TEM00 mode laser using a YVO4/Nd:YVO4 composite crystal

A effective continuous-wave (CW), high power laser generated using a YVO₄/Nd:YVO₄ composite crystal is presented. 18.8 W output power in multi-mode has been achieved with a maximum absorbed pump power of 31.2 W, corresponding to an optical-to-optical efficiency of 60.26%. In TEM₀₀ mode operation, 15.1 W output power also has been achieved with the maximum absorbed pump power of 31.2 W, corresponding to an optical-to-optical efficiency of 47.69%. With a 200 mm focal-length positive lens and using the moving knife-edge method, the beam quality factor is measured to be M² = 1.2 for TEM₀₀ mode beam.     

Nd:YVO₄ amplifier for ultrafast low-power lasers

An Nd:YVO₄ amplifier consisting of two modules end pumped at 808?nm at 30?W total absorbed power has been designed for efficient, diffraction-limited amplification of ultrafast pulses from low-power seeders. We investigated amplification with a 50?mW, 7?ps Nd:YVO₄ oscillator, a 2?mW, 15?ps Yb fiber laser, and a 30?mW, 300?fs Nd:glass laser. Output power as high as 9.5?W with 8?ps pulses was achieved with the 250?MHz vanadate seeder, whereas the 20?MHz fiber laser was amplified to 6?W. The femtosecond seeder allowed extracting Fourier-limited 4?ps pulses at 7?W output power. To our knowledge, these are the shortest pulses from any Nd:YVO₄ laser device with at least 7?W output power. This suggests a novel approach to exploit the gain bandwidth of vanadate amplifiers with high output power levels. Such amplifier technology promises to offer an interesting alternative to high-power thin disk oscillators at few picoseconds duration, as well as to regenerative amplifiers with low-repetition-rate fiber seeders.     

Investigation of Nd:YVO4/YVO4 composite crystal and its laser performance pumped by a fiber coupled diode laser

Thermal effect control is critical to scale the output power of diode end-pumping solid lasers to several watts up and beyond. Diffusion bonding crystal has been demonstrated to be an effective method to relieve the thermal lens for the end-pumping laser crystal. The temperature distribution and thermal lens in Nd:YVO₄/YVO₄ composite crystal was numerically analyzed and compared with that of Nd:YVO4 crystal in this paper. The end-pumping Nd:YVO₄/YVO₄ composite crystal laser was set up and tested with z cavity. The maximum output power of 9.87 W at 1064 nm and 6.14 W at 532 nm were obtained at the pumping power of 16.5 W. The highest optical-optical conversion efficiencies were up to 60% at 1064 nm and 40% at 532 nm, respectively.     

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.     

Passive Q-switching of a diode-side-pumped Nd-doped mixed gadolinium yttrium vanadate bounce laser

High power passive Q-switching was achieved with a pulse width of 18–32 ns by using a diode-side-pumped Nd:Gd_0.6Y_0.4VO₄ bounce amplifier. An average output power of > 8 W was obtained at a pump power of 39 W. The peak power of the Q-switched output was adjusted within 1.9–5.2 kW by changing the Nd concentration. The mixed vanadates showed significantly higher Q-switching performances in comparison with pure Nd:GdVO₄. PACS 42.55.Xi; 42.60.Gd; 42.60.Da     

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.     

High-power continuous-wave doubly resonant all-intracavity sum-frequency mixing deep blue laser at 447 nm

In this paper, a high-power continuous-wave deep blue laser at 447 nm with intracavity tripling was achieved. The deep blue laser at 447 nm is obtained by using a doubly cavity, and type-II critical phase matching KTP crystal for intracavity sum-frequency mixing. Through designing of the cavity, the optimum matching of modes and gains for the two wavelengths was obtained. With incident pump power of 30 W for the Nd:YVO₄ crystal and 16 W for the other Nd:YVO₄ crystal, the deep blue laser output of 3.5 W at 447 nm with TEM₀₀ mode was obtained, the beam quality M² value was equal to 1.8 in both horizontal and vertical directions at the maximum output power, and the power stability is better than 3% at the maximum output power during half an hour. The experimental results show that the intracavity sum-frequency mixing by doubly resonant is an effective method for high-power blue laser.