Diode-pumped Nd:BaY2F8 picosecond laser

Picosecond pulse generation at 1050 nm by a diode-pumped Nd:BaY₂F₈ (Nd:BaYF) active crystal has been investigated under low-power pumping (440 mW absorbed). The sample was oriented along the optical axes and cut at Brewster angle for y-axis laser polarization to minimize birefringence effects. Stable passive mode-locking operation has been achieved by inverse saturable absorption with 80-mW output power and 3.7-ps pulses.     

Efficient and compact intracavity-frequency-doubled Nd:GdVO4/KTP laser end-pumped by a fiber-coupled laser diode

A compact and efficient diode-pumped intracavity-frequency-doubled Nd:GdVO₄/KTP green laser is demonstrated with a flat–flat cavity design. With a 1.3 at. % Nd³⁺-doped GdVO₄ crystal and pumped at the weak-absorption peak of 806 nm, the second-harmonic output power at 532 nm was measured to be 1.95 W at an incident pump power of 8.4 W, corresponding to an optical conversion efficiency of 23.2%. The output characteristic at the fundamental wavelength of 1.063 μm was investigated with two different pump wavelengths. More than 4.5-W output power was generated when the laser was pumped at 806.2 nm. Received: 26 July 2000 / Revised version: 18 September 2000 / Published online: 7 February 2001     

Optical properties and highly efficient laser oscillation of Nd:YAG ceramics

Optical absorption, emission spectra have been measured for polycrystalline Nd-doped Y₃Al₅O₁₂ ceramics. Fluorescence lifetimes of 257.6 μs, 237.6 μs, 184.2 μs and 95.6 μs have been obtained for 0.6%, 1%, 2% and 4% neodymium-doped YAG ceramics, respectively. For the first time, highly efficient laser oscillation at 1064 nm has been obtained with this kind of ceramics. Slope efficiency of 53% has been achieved on a uncoated 4.8-mm thick 1% Nd:YAG ceramics sample. Optical to optical conversion efficiency is 47.6%. Laser oscillation has also been obtained with a 2% Nd:YAG ceramics. The optical properties and laser output results have been compared with that of Nd:YAG single crystal grown by the Czochralski method. Almost identical results have been achieved including laser experiments results. But fabrication of Nd:YAG ceramics is much easier compared to the single-crystal growth method. And also large size (now of about 400 mm diameter×5 mm is available) and high-concentration (>1%) Nd:YAG ceramics can be fabricated. The results show that this kind of Nd:YAG ceramics is a very good alternative to Nd:YAG single crystal. Received: 20 April 2000 / Published online: 16 August 2000     

A Compact All-Solid-State 630-ps 9.43-kHz High Power Nd：YAG/Nd：YVO4 Hybrid Laser System

We present a simple and compact design for an all-solid-state laser amplifier system which can output 9.43-kHz 630-ps, 3.5-W pulse trains under 20 W absorbed pumping power. The excellent matching between the repetition of its seed source and the fluorescence lifetime of the amplifying medium makes it quiet efficient for the four-pass amplifier to be pumped in cw mode without need of any synchronization device between the oscillator and the amplifier. The entire setup just covers an area of 55 × 25 cm^2. The output average power fluctuation is less than ±1.5% within 10min and 3% within 6h.     

A Diode-Stack End-Pumped Electro-Optically Q-Switched Nd:YAG Slab Oscillator--Amplifier System

A laser diode-stack end-pumped electro-optically Q-switched Nd：YAG slab oscillator-amplifier system with neardiffraction-limited output is demonstrated by a stable-unstable hybrid resonator. The average power of 100 W at a repetition rate of lOkHz with a pulse width 14.7ns and average power of 76.3 W at a repetition rate of 5kHz with a pulse width of 10.2ns are measured. At the repetition rate of 10 kHz and at an output power of 89 W, the beam quality factors M^2 in the unstable and stable directions are 1.3 and 1.5, respectively.     

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.     

Efficient Pumping Scheme by Direct Excitation of Upper Laser Level in Nd:CNGG

We report an efficient pumping scheme which involves a direct excitation of the upper lasing level of a four-level laser in a Nd-doped Ca₃(NbGa)_2-xGa₃O₁₂ (Nd:CNGG) by using a tunable Ti:sapphire, 700-920nm, cw pump source. The slope efficiency is improved from 10.5% of the traditional band pumping at 808nm to 21.8% of the direct pumping at 882nm. The influence of pumping wavelength on lasing is discussed. We present a scheme of double pumping for lasing.     

High-power sub-10-fs Ti:sapphire oscillators

Received: 10 March 1997/Revised version: 16 April 1997     

All-solid-state cavity-dumped sub-5-fs laser

Received: 19 March 1997/Revised version: 9 May 1997     

Characteristics of Nd：GdVO4 Laser with Different Nd-Doping Concentrations

We report the properties of a compact diode-pumped continuous-wave Nd：GdV04 laser with a linear cavity and different Nd-doped laser crystals. In a 0.2at.% Nd-doped Nd：GdVO4 laser, 1.54 W output laser power is achieved at 912nm wavelength with a slope efficiency of 24.8% at an absorbed pump power of 9.4W. With 0.3at.% Nd-doping concentration, we can obtain the either single-wavelength emission at 1064nm or 912nm or the dual-wavelength emission at 1064nm and 912nm by controlling the incident pump power. From an incident pump power of 11.6 W, the 1064nm emission between ^4Fa/2 and ^4I11/2 is suppressed completely by the 912nm emission between ^4Fa/2 and ^4I9/2. We obtain 670 mW output of the 912nm single-wavelength laser emission with a slope efficiency of 5.5% by taking an incident pump power of 18.4 W. Using a Nd：GdV04 laser with 0.4at.% Nd-doping concentration, we obtain either the single-wavelength emission at 1064nm or the dual-wavelength emission at both 1064nm and 912nm by increasing the incident pump power. We observe a strong competition process in the dualavelength laser.     

Simultaneous dual-wavelength Q-switched Nd:YAG laser operating at 1.06 μm and 946 nm

Considering the reabsorption loss of the quasi-three level system and the unsaturable loss of the saturable absorber, we obtained the operating condition of a diode-pumped simultaneous dual-wavelength Q-switched Nd:YAG laser operating at 1.06 μm and 946 nm. The dual-wavelength pulsed laser was realized successfully through adaptive coating design of the cavity mirrors. As much as 1.6 W total average output power of the dual-wavelength at 1.06 μm and 946 nm was achieved at the incident pump power of 14.2 W with an optical conversion efficiency of 11.3%.     

Thermal effects investigation and cavity design in passively mode-locked Nd:YVO4 laser with a SESAM

A diode-pumped passively mode-locked Nd:YVO₄ laser with a five-mirror folded cavity is presented by using a semiconductor saturable absorber mirror (SESAM). The temperature distribution and thermal lensing in laser medium are numerically analyzed to design a special cavity which can keep the power density on SESAM under its damage threshold. Both the Q-switched and continuous-wave mode-locked operation are experimentally realized. The maximum average output power of 8.94 W with a 9.3 ps pulse width at a repetition rate of 111 MHz is obtained under a pump power of 24 W, correspondingly the optical slope efficiency is 39.2%.     

Laser action in a cw diode-pumped Nd:Ca3Sc2Ge3O12 crystal

CW diode-pumped laser operation of Nd³⁺ in Ca₃Sc₂Ge₃O₁₂ (CaSGG) single garnet crystal has been demonstrated for the first time. We measured an 18% slope efficiency and 2.7-nm tunability with two different laser cavities. A spectroscopic characterization of our sample has also been performed including the absorption cross section in the 800-nm region and the emission cross section and radiative lifetime of the upper laser level. Received: 7 December 1999 / Revised version: 6 February 2000 / Published online: 27 April 2000     

Passively Q-switched laser performance of c-cut Nd:Gd0.63Y0.37VO4 crystal

Passively Q-switched c-cut Nd:Gd_0.63Y_0.37VO₄ laser performance at 1.06 μm was demonstrated with Cr⁴⁺:YAG as saturable absorbers for the first time to our knowledge. This c-cut mixed crystal was found to have large energy storage capacity. The shortest pulse width, largest pulse energy, and highest peak power were obtained to be 6.6 ns, 201.7 μJ, and 30.6 kW, respectively.     

Passive Q-switching at 1.54 μm of an Er–Yb: GdCa4O(BO3)3 laser with a Co2+: MgAl2O4 saturable absorber

We report, for the first time to our knowledge, efficient passive Q-switching of the 1.54-μm laser transition in an Er–Yb-doped crystalline medium. The laser configuration is a compact microchip design that is suitable for a range of practical applications such as range finding and lidar. The slope efficiency of 11.6%, pulse duration of 5–6 ns and average output power of 88 mW are all comparable with standard Er–Yb:glass lasers.     

Passively Q-Switched Nd：KLuW Laser with Semiconductor Saturable Absorber

We demonstrate a passively Q-switched Nd：KLu W laser with a semiconductor sat urable absorber mirror （SESAM） at wavelength 1070 nm. At a pump power of 1.3 W, the pulse width is measured to be about 17ns with repetition rate of lOkHz and with the average output power of 260roW. To our knowledge, this is the first demonstration of Nd：KLuW used for passively Q-switched laser with an SESAM.     

Diode-pumped cw tunable two-frequency YAG:Nd<Superscript>3+</Superscript> laser with coupled resonators

Using the mode splitting that can be achieved by exploiting the effect of photoelasticity and the mode selection properties of coupled resonators, single- and two-frequency operation of a diode pumped cw YAG:Nd³⁺ laser was observed. In the two-frequency case, a regime with two orthogonal linearly polarized modes was realized. The frequency difference between the adjacent modes could be varied from 50 MHz to 8.4 GHz. A maximum laser output power of 12 mW was achieved at a pump level of 240 mW . Received: 1 November 2002 / Revised version: 14 January 2003 / Published online: 19 March 2003 RID="*" ID="*"Corresponding author. Fax: +375-17/2840-879, E-mail: ryabtsev@dragon.bas-net.by     

Q-switched Yb 3+ :YVO 4 laser with Raman self-conversion

We report the efficient continuous-wave (CW) and Q-switched laser operation of a diode-pumped Yb:YVO₄ laser. A CW output power of 1 W with a slope efficiency of 59% with respect to absorbed pump power was demonstrated. Passively Q-switched with a Cr⁴⁺:YAG saturable absorber, a Yb:YVO₄ laser with Raman conversion was demonstrated. Q-switched 18.7- J pulses with a pulse duration of 17 ns and a peak power up to 1 kW were obtained at 1018-nm fundamental wavelength and 3.6- J pulses with a pulse duration of 6 ns and a peak power of about 0.6 kW were obtained at 1119.5-nm first-Stokes wavelength.This revised version was published online in March 2005. In the previous version, the published online date was missing     

Reflective carbon nanotube as the saturable absorber for mode-locked 1064 nm laser

With a reflective single-walled carbon nanotube as the saturable absorber, a laser diode-pumped passively mode-locked Nd:YVO₄ laser at 1064 nm was realized for the first time. The pulse duration of 12 ps was produced with a repetition rate of 83.7 MHz. The peak power and the single pulse energy of the mode-locking laser were 1.28 kW and 15.4 nJ, respectively.     

Additive pulse mode-locked Nd: YAG laser

Additive pulse mode locking applied to lamppumped Nd: YAG lasers results in an attractive source of picosecond pulses at 1.06 m or 1.32 m with average powers at the Watt level. We provide detailed information on construction and operation and give data on performance. A modified active stabilization scheme allows not only improved stability of operation but also insight into the dynamics of pulse formation.