Sergio V. Marchese

Powerful red-green-blue laser source pumped with a mode-locked thin disk laser

We present a red-green-blue laser source with average powers of 8 W in the red, 23 W in the green, and 10.1 W in the blue. The entire pump power for the nonlinear conversion stages is provided by a single laser oscillator without any amplifier stages. Our system does not require any synchronized cavities, and all nonlinear crystals except one are critically phase matched at room temperature.

Femtosecond thin disk laser oscillator with pulse energy beyond the 10-microjoule level

We report on a passively mode-locked Yb:YAG thin disk laser oscillator that generates 11.3-microJ pulses without the use of any additional external amplification. A repetition rate of 4 MHz is obtained using a 23.4-m-long multiple-pass cavity that extends the resonator length to a total of 37 m. The nearly transform-limited pulses at 45 W of average output power have a duration of 791 fs with a 1.56-nm-broad spectrum centered at 1030 nm. The laser is operated in a helium atmosphere to eliminate the air nonlinearity inside the resonator that previously limited the pulse energy.

High precision optical characterization of semiconductor saturable absorber mirrors

Precise semiconductor saturable absorber mirrors (SESAM) design has enabled modelocked lasers with >100 GHz pulse repetition rate or >10 muJ pulse energy. We discuss a new method for wide dynamic range nonlinear reflection measurements of SESAMs with <0.05% accuracy.

Efficient femtosecond high power Yb:Lu2O3 thin disk laser

We demonstrate the first passively mode-locked thin disk laser based on Yb:Lu(2)O(3). The laser generates 370-fs pulses with 20.5 W of average power in a diffraction-limited beam (M(2) < 1.1). The nearly transform-limited pulses have a spectral bandwidth of 3.4 nm centered near 1034 nm. With slightly longer pulses (523 fs) we obtained 24 W of average power at a pump power of 56 W, resulting in an optical-to-optical efficiency of 43%, which is higher than for any previously mode-locked thin disk laser.

Pulse energy scaling to 5 μJ from a femtosecond thin disk laser

We report an increase in pulse energy to 5.1μJ obtained directly from a femtosecond diode-pumped Yb:YAG thin disk laser without external amplification. Stable passive mode locking was obtained with a semiconductor saturable absorber mirror (SESAM). The laser delivers 63W of average output power in a nearly diffraction-limited beam (M2=1.1) at a center wavelength of 1030nm. The pulse repetition rate is 12.3MHz, and the pulses have a duration of 800fs, which results in a peak power of 5.6MW. The laser was operated in a box flooded with helium because the nonlinearity of air was found to be a limiting factor for the stability of the pulse formation at increasing pulse energies.

Analysis of nonlinear wavelength conversion system for a red-green-blue laser-projection source

We analyze the physical processes in the nonlinear wavelength conversion stages of a recently demonstrated red-green-blue (RGB) laser source, which generated > or = 8 W of average power in each color. The system is based on an infrared femtosecond mode-locked laser and contains a frequency doubler, a parametric generator, a parametric amplifier, and two sum-frequency conversion stages. It does not require any resonant cavities, external laser amplifiers, or nonlinear crystals operated at elevated temperatures; therefore it appears to be more practical than other previously demonstrated RGB laser sources. However, the optimization of the overall system is nontrivial, because pump depletion, birefringence, and temporal walk-off in the first conversion stages lead to spatial and temporal distortion of the interacting beams in the subsequent nonlinear conversion stages. This leads to the interaction of spatially and temporally distorted beams in the later conversion stages. By using a numerical simulation of the nonlinear conversion processes based on a Fourier-space method in one temporal and two transverse spatial dimensions, we can fully take into account these effects. We analyze and discuss the physical effects in the different conversion stages and describe the optimization of the overall system performance.

Passively mode-locked thin disk lasers reach 10 microjoules pulse energy at megahertz repetition rate and drive high field physics experiments

The direct generation of high energy pulses with a diode-pumped solid-state laser oscillator is a promising approach to enable the multi-megahertz operation of numerous applications in science and industry. Thin disk lasers enable the required average power with excellent beam quality, such that passive mode locking with a semiconductor saturable absorber mirror (SESAM) can be achieved. Using this concept, the authors have recently been able to reach a pulse energy as high as 5.1 muJ at 12 MHz repetition rate from an Yb:YAG thin disk oscillator. This significant increase over previous results was made possible by realizing the importance of the nonlinearity of air inside a thin disk laser cavity. To eliminate the airs contribution to the nonlinearity, the laser was covered with a box which then was flooded with helium. Here a further increase in pulse energy to 11 muJ is presented. The existing 40.7 MHz laser cavity presented was extended to a total of 37 m, by inserting a 23.4 m long multiple-pass cavity (MPC) and a simple 4f extension using curved mirrors with 5000 mm radius of curvature. This resulted in a repetition rate of 4 MHz, at which we achieved an average power of 45 W when operated in the box flooded with helium. The sech2-shaped pulses had a FWHM-duration of 791 fs and a spectral bandwidth of 1.56 nm, resulting in a time-bandwidth product of 0.35 (Fourier-limit: 0.315). The beam quality was nearly diffraction-limited with an M2-value of 1.1 (measured at 9.4 muJ).

First High Harmonic Generation (HHG) in a Photonic Crystal Fiber (PCF)

We generate the 7th-13th harmonic of ≈800 nm by propagating 30-fs pulses at >1014W/cm2through a xenon-filled hollow-core PCF. The extremely low HHG threshold of 0.4 µJ would be achievable by multimegahertz solid-state lasers.

Femtosecond thin disk lasers with ≫10 μJ pulse energy

We present a SESAM-modelocked Yb:YAG laser generating nearly transform-limited femtosecond pulses with 11-muJ energy at 4 MHz repetition rate and excellent beam quality. We discuss the key challenges for further increase of the pulse energy.

Efficient Femtosecond Yb:Lu 2 O 3 Thin Disk Laser

We demonstrate the first mode-locked Yb:Lu2O 3 thin disk laser, obtaining 370-fs pulses with 20.5 W average power. The 43% optical-to-optical efficiency obtained with 523-fs pulses is higher than for previous mode-locked thin disk lasers.