Femtosecond 5-W Yb:KGW slab laser oscillator pumped by a single broad-area diode and its application as supercontinuum source

We demonstrate a novel and very simple design for an efficient high-power femtosecond Yb:KGW slab laser oscillator. The laser is capable of producing output powers of more than 5 W at 44-MHz repetition rate and pulse widths as short as 161 fs with a nearly diffraction limited beam and an optical-to-optical efficiency of more than 28%. The laser is pumped by a single broad-area laser diode and employs simple pump optics consisting of three lenses. The laser output power is distributed between two beams and single or combined outputs are discussed. In combination with a tapered fiber the laser was used to generate femtosecond supercontinua with up to 1.3-W average power and spectra spanning from 420 to over 1750 nm.     

Femtosecond and continuous-wave laser performance of a diode-pumped Yb3+:CaYAlO4 laser

The cw and femtosecond laser operations of Yb(3+):CaYAlO(4) (Yb:CYA) are demonstrated. The laser emitted a maximum cw power of 1.94 W with a slope efficiency (η(slope)) of 71% and an optical-to-optical efficiency (η(opt)) of 51%. Under mode-locking operation, the laser emitted near transform-limited pulses with 156 fs pulse width, 8.1 nJ pulse energy and 0.74 W average power. The η(slope) and η(opt) of the mode-locked laser were 37% and 20%, respectively.     

7.6-W diode-pumped femtosecond Yb:KGW laser

We have demonstrated a high power diode-pumped mode-locked femtosecond Yb:KGW laser with semiconductor saturable absorber mirror(SESAM). By using an output coupler with 10% transmittance, the laser delivered 160-fs pulses with average output power of 7.6 W at a repetition rate of 78 MHz, corresponding to pulse energy of 97 nJ and peak power of 606 kW.     

Polarization-tunable Yb:KGW laser based on internal conical refraction

Using internal conical refraction, we demonstrate an Yb:KGW laser where the polarization state can be arbitrarily altered without any additional cavity components. The extinction ratio can also be altered between 1:1 and 40:1. The maximum output power achieved was 8.6 W at a slope efficiency of 60.5% with respect to incident pump power. This equals the power performance of a standard Yb:KGW laser used for reference.     

Efficient and tunable diode-pumped femtosecond Yb:glass lasers

Diode-pumped Yb:phosphate and Yb:silicate glass lasers have been passively mode locked for the first time to the authors' knowledge. Reliable self-starting mode locking without critical cavity alignment has been achieved with intracavity semiconductor saturable-absorber mirrors and soliton mode locking. We generated pulses as short as 58 fs with the Yb:phosphate laser and 61 fs with the Yb:silicate laser at average output powers of 65 and 53 mW, respectively. The pulse repetition rate was 112 MHz. Additionally, we demonstrated tunability of femtosecond pulses from 1025 to 1065 nm for the Yb:phosphate and from 1030 to 1082 nm for the Yb:silicate glasses. The highest mode-locked output power was 405 mW, with 183-fs pulses from the phosphate glass. The diode pump power was 1.68 W, corresponding to 24% optical-to-optical efficiency. The highest cw output power was 510 mW at the same incident pump power.     

Laser performance of Yb:GdCa<Subscript>4</Subscript>O(BO<Subscript>3</Subscript>)<Subscript>3</Subscript> compared to Yb:KGd(WO<Subscript>4</Subscript>)<Subscript>2</Subscript> under diode-bar pumping

A study of Yb:GdCOB under diode-bar pumping has been performed and the results are compared, experimentally and theoretically, with Yb:KGW in the same cavity. An output power of 7.3 W and a slope efficiency of 57.4% were obtained. Self-frequency-doubling experiments are also discussed.     

Diode-pumped efficient continuous-wave Yb:Y3Ga5O12 laser at 1035 nm

An efficient diode-pumped Yb:Y3Ga5O12 (Yb:YGG) laser was demonstrated by using a high-quality Yb:YGG crystal grown by the optical floating zone method. Continuous-wave laser power up to 2.65?W had been obtained under an incident pump power of 6.71?W at 970?nm, corresponding to an optical-to-optical efficiency of 39.5% and maximum slope efficiency of 84.5%. A modeling calculation of the Yb:YGG laser was also performed, and the theoretical results were consistent with the experimental results.     

Thermal analysis and efficient high power continuous-wave and?mode-locked thin disk laser operation of Yb-doped sesquioxides

We report on thermal conductivity analysis and thin disk laser power scaling of Yb:Lu₂O₃, Yb:Sc₂O₃, and Yb:LuScO₃. Using a volume Bragg-grating stabilized pump diode we have obtained cw output powers up to 301?W with optical-to-optical efficiencies of up to 73%. In mode-locked operation of an Yb:Lu₂O₃ thin disk laser 141?W of average output power with 738 fs pulses and an optical-to-optical efficiency of 40% were achieved.     

Compact laser source for high-power white-light and widely tunable sub 65 fs laser pulses

We demonstrate an Yb:KGW femtosecond solitary mode-locked laser oscillator, which is used as a pump source for tapered fibers to generate white-light laser pulses with an average output power of up to 2.5 W and a spectral bandwidth of over 1000 nm. By spectrally filtering these pulses and subsequent compression of the filtered pulses with a prism sequence, we are able to generate ultrashort laser pulses with durations between 26 and 65 fs that are tunable from 600 to 1450 nm and with tens to several hundreds of milliwatts of average power.     

Compact diode-pumped 1.1 kW Yb:YAG Innoslab femtosecond amplifier

We demonstrate a compact diode-pumped Yb:KGW femtosecond oscillator-Yb:YAG Innoslab amplifier master oscillator power amplifier (MOPA) with nearly transform-limited 636 fs pulses at 620 W average output power, 20 MHz repetition rate, and beam quality of M(x)(2) = 1.43 and M(y)(2) = 1.35. By cascading two amplifiers, we attain an average output power of 1.1 kW, a peak power of 80 MW, and a 615 fs pulse width in a single linearly polarized beam. The power-scalable MOPA is operated at room temperature, and no chirped-pulse amplification technique is used.     

Efficient laser operation of Yb:Lu3Ga5O12 garnet crystal

Efficient laser operation is demonstrated at room temperature with a new Yb:Lu3Ga5O12 garnet crystal. A continuous-wave output power of 5.36 W is generated at a center oscillation wavelength of 1041 nm, with an optical-to-optical efficiency of 51% and the slope efficiency of 63%. In passively Q-switched operation, the maximum average output power reaches 4.0 W (center wavelength of 1034 nm) at a repetition rate of 71 kHz, with optical-to-optical and slope efficiencies measured to be 40% and 50%, respectively. Laser pulses of 26 ns duration are generated with a pulse energy of 91 μJ and peak power of 3.5 kW.     

Highly efficient CW intracavity frequency-doubled Yb:YAG-LBO laser at 515 nm under 968 nm diode laser pumping

We describe the output performances of the 1030 nm transition in Yb:YAG under in-band pumping with diode laser at the 968 nm wavelength. An end-pumped Yb:YAG crystal yielded 1.93 W of continuous-wave (CW) output power for 9.1 W of absorbed pump power. The slope efficiency with respect to the absorbed pump power was 23.6%. Furthermore, 205 mW 515 nm green light was acquired by frequency doubling, resulting in an optical-to-optical efficiency with respect to the absorbed pump power of 2.7%. Comparative results obtained for the pump with diode laser at 940 nm are given in order to prove the advantages of the in-band pumping.     

A 515-nm laser-pumped idler-resonant femtosecond BiB3O6 optical parametric oscillator

We report on an idler-resonant femtosecond optical parametrical oscillator(OPO)based on BiB₃O₆(BiBO)crystal,synchronously pumped by a frequency-doubled,mode-locked Yb:KGW laser at 515 nm.The idler wavelengths of OPO can be tuned from 1100 nm to 1540 nm.At a repetition rate of 75.5 MHz,the OPO generates as much as 400 mW of idler power with 3.1 W of pump power,the corresponding pulse duration is 80 fs,which is 1.04 times of Fourier transform-limited(FTL)pulse duration at 1305 nm.In addition,the OPO exhibits excellent beam quality with M²<1.8 at 1150 nm.To the best of our knowledge,this is the first idler-resonant femtosecond OPO pumped by 515 nm.     

High-power 200 fs Kerr-lens mode-locked Yb:YAG thin-disk oscillator

We demonstrate a power-scalable Kerr-lens mode-locked Yb:YAG thin-disk oscillator. It delivers 200 fs pulses at an average power of 17 W and a repetition rate of 40 MHz. At an increased (180 W) pump power level, the laser produces 270 fs 1.1 μJ pulses at an average power of 45 W (optical-to-optical efficiency of 25%). Semiconductor-saturable-absorber-mirror-assisted Kerr-lens mode locking (KLM) and pure KLM with a hard aperture show similar performance. To our knowledge, these are the shortest pulses achieved from a mode-locked Yb:YAG disk oscillator and this is the first demonstration of a Kerr-lens mode-locked thin-disk laser.     

Second Harmonic Generation in Microstructured Barium Titanate

We investigate the second harmonic generation under femtosecond pulse-periodic laser radiation in barium titanate in the form of ceramics, in pores of a globular photonic crystal, and in a water colloidal suspension. We measure the dependence of the second harmonic radiation intensity on the incident laser power. Excitation of the second harmonic was carried out by powerful (10⁸ W) pulses of a solid-state Yb:KGW laser (wavelength, 1,026 nm) operating at 200 kHz. We estimate the efficiency of the second harmonic generation in various microstructured phases of barium titanate and show that the threshold of plasma formation in a suspension of barium titanate microparticles in water is substantially higher than in ceramics and in the ferroelectric photonic crystal. The second-harmonicgeneration power can be significantly increased in a water suspension of barium titanate microparticles.     

10% Yb3+-Lu2O3 ceramic laser with 74% efficiency

We demonstrate laser oscillation at 1080 nm with more than 16 W of output power and with an optical-to-optical slope efficiency of up to 74% using a 10% Yb3+ doped Lu2O3 ceramic made by hot pressing. This represents the highest output power and efficiency obtained for a Yb3+ doped Lu2O3 ceramic and demonstrates the feasibility for power scaling.     

Study of Yb:YVO<Subscript>4</Subscript> lasers end-pumped by a 985-nm diode laser

Efficient continuous-wave operation is demonstrated at room temperature with a Yb:YVO₄ laser end pumped by a 985-nm diode. An output power of 2.46 W is generated at the highest available absorbed pump power of 6.2 W, with an optical-to-optical and slope efficiency of 40 and 76%, respectively. A theoretical calculation of the laser characteristics agrees closely with the experimental results.     

Generation of 287 W, 5.5 ps pulses at 78 MHz repetition rate from a cryogenically cooled Yb:YAG amplifier seeded by a fiber chirped-pulse amplification system

We generate linearly polarized, 287 W average-power, 5.5 ps pulses using a cryogenically cooled Yb:YAG amplifier at a repetition rate of 78 MHz. An optical-to-optical efficiency of 41% is obtained at 700 W pump power. A 6 W, 0.4 nm bandwidth picosecond seed source at 1029 nm wavelength is constructed using a chirped-pulse fiber amplification chain based on chirped volume Bragg gratings. The combination of a fiber amplifier system and a cryogenically cooled Yb:YAG amplifier results in good spatial beam quality at large average power. Low nonlinear phase accumulation as small as 5.1 x 10(-3) rad in the bulk Yb:YAG amplifier supports power scalability to a > 10 kW level without being affected by self-phase modulation. This amplification system is well suited for pumping high-power high-repetition-rate optical parametric chirped-pulse amplifiers.     

Diode-pumped sub-100 fs Kerr-lens mode-locked Yb3+:Sc2O3 ceramic laser

Diode-pumped Kerr-lens mode-locked laser operations of Yb3+:Sc2O3 ceramics have been achieved. 92 fs pulses with the average power of 850 mW under 3.89 W incident pump power were obtained at a center wavelength of 1042 nm. The optical-to-optical efficiency was 21.9%. 90 fs pulses with the average power of 160 mW were also obtained at a center wavelength of 1092 nm. To our knowledge, this is the first demonstration of a Kerr-lens mode-locked Yb3+:Sc2O3 laser.     

Harmonically pump a femtosecond optical parametric oscillator to 1.13 GHz by a femtosecond 515 nm laser

We demonstrate a harmonically pumped femtosecond optical parametric oscillator(OPO)laser using a frequency-doubled mode-locked Yb:KGW laser at a repetition rate of 75.5 MHz as the pump laser.Based on a bismuth borate nonlinear crystal,repetition rates up to 1.13 GHz are realized,which is 15 times that of the pump laser.The signal wavelength is tunable from 700 nm to 887 nm.The maximum power of the signal is 207 m W at the central wavelength of 750 nm and the shortest pulse duration is 117 fs at 780 nm.The beam quality(M^2 factor)in the horizontal and vertical directions of the output beam are 1.077 and 1.141,respectively.