Johannes A. L'huillier

High energy cw-diode pumped Nd:YVO4 regenerative amplifier with efficient second harmonic generation.

We report on a 888 nm diode-pumped Nd:YVO4 regenerative amplifier with up to 33.7 W output power with a repetition-rate of 20 kHz and an adjustable pulse duration between 217 ps and 1 ns. This setup allowed for efficient second harmonic generation with an efficiency of up to 79%.

All solid-state 191.7 nm deep-UV light source by seventh harmonic generation of an 888 nm pumped, Q-switched 1342 nm Nd:YVO₄ laser with excellent beam quality.

In this paper we report on the realization of a deep-UV light source using the 1.3 μm transition of neodymium as pumping wavelength. The 191.7 nm radiation was obtained by generating the seventh harmonic of a high-power Q-switched 1342 nm Nd:YVO4 laser. A cesium lithium borate crystal was used for sum frequency mixing of the sixth harmonic and the fundamental. With a total of four conversion stages, up to 240 mW were achieved, with excellent beam quality at 155 mW (M2 < 1.7) and 190 mW (M2 < 1.9).

Fabrication of ridge waveguides in LiNbO 3

We have fabricated ridge waveguides in lithium niobate with sidewall roughness of 14 nm (rms) and sidewall angles of more than 71°. The use of thick electroplated metal masks for reactive ion etching (RIE) makes it possible to manufacture ridge structures with several microns in height. For light confinement towards the substrate we investigate direct heterobonding techniques. Due to the expected low transmission losses we envision future applications in the field of quantum optics.

High-average power Nd:YVO4 regenerative amplifier seeded by a gain switched diode laser

We report on a Nd:YVO4 regenerative amplifier (RA), end pumped by 888 nm-diode lasers. The output power was about 46W at repetition rates from 150 to 833kHz with an M2-factor of 1.2. The amplifier was seeded by a gain switched diode laser, generating pulses with a duration of 65 ps and a pulse energy of ≈ 5 pJ. The high gain of the RA of more than 70 dB provides amplified pulse energies as high as 180μJ. Bifurcations of the pulse energy could be avoided. Pulse amplitude fluctuations of only 1.2% for 10,000 consecutive pulses were measured. The long term output power stability of the laboratory setup was 0.3%.

Second harmonic generation in the new nonlinear optical material BiB/sub 3/O/sub 6/

Summary form only given. The monoclinic BiB/sub 3/O/sub 6/ is a new nonlinear optical material. Recently, large BiB/sub 3/O/sub 6/ crystals have been grown with good optical quality. Meanwhile, the Sellmeier coefficients were published an calculations indicated the suitability for nonlinear applications. We report on an investigation of the properties of this material for frequency doubling (SHG) of e.g. Nd:YAG laser radiation (1064 nm). The 5 mm long crystal used in these investigations was cut in the y-z-plane. The two crystal facets were AR coated for 1064 nm and 532 nm. Important parameters for efficient SHG are the linear losses at 1064 nm and the effective nonlinearity. Both parameters were measured across the crystals aperture (of 3/spl times/3 mm) with a spatial resolution of 120 /spl mu/m. In addition, we determined the temperature and the angular acceptance bandwidth.

Laser drilling of carbon fiber reinforced plastics (CFRP) by picosecond laser pulses: comparative study of different drilling tools

Carbon fiber reinforced plastic (CFRP) as a lightweight material with superior properties is increasingly being used in industrial manufacturing. Using ultrashort laser pulses can improve the quality in cutting or drilling applications, but at high power levels it is more complicated to maintain the accuracy and precision in CFRP drilling. According to the application requirements for the extent of the heat affected zone, the geometric precision and the productivity different drilling tools can be used. Therefore we report on the application of three different beam delivery systems to drilling processes of CFRP: Galvanometer scanner, trepanning head and diffractive optical elements.

Laser microstructuring of congruent lithium niobate by UV ps-pulses

We present single shot experiments at different pulse energies for LiNbO₃ on c⁺-side and c^--side by using a laser wavelength of 355 nm and a pulse duration of about 10 ps. Furthermore, we demonstrate laser micromachined grooves with high spatial pulse overlap on the c⁺-side of LiNbO₃. Here a (rms) sidewall roughness as low as 20 nm has been achieved at an ablation depth of 1.2μm.

Generation of Powerful Tunable Mid-Infrared Picosecond Laser Radiation Using Frequency Conversion in Periodically Poled Lithium Niobate

The generation of tunable mid-infrared picosecond laser radiation in the spectral range from 3-5µm by nonlinear frequency conversion in PPLN is reported. More than 3W output power at 3µm and 1W at 4.5µm were achieved.

Fabrication of low-loss ridge waveguides in z-cut lithium niobate by combination of ion implantation and UV picosecond laser micromachining

Ridge waveguides in ferroelectric materials like LiNbO3 attended great interest for highly efficient integrated optical devices, for instance, electro-optic modulators, frequency converters and ring resonators. The main challenges are the realization of high index barrier towards the substrate and the processing of smooth ridges for minimized scattering losses. For fabricating ridges a variety of techniques, like chemical and wet etching as well as optical grade dicing, have been investigated in detail. Among them, laser micromachining offers a versatile and flexible processing technology, but up to now only a limited side wall roughness has been achieved by this technique. Here we report on laser micromachining of smooth ridges for low-loss optical waveguides in LiNbO3. The ridges with a top width of 7 µm were fabricated in z-cut LiNbO3 by a combination of UV picosecond micromachining and thermal annealing. The laser processing parameters show a strong influence on the achievable sidewall roughness of the ridges and were systematically investigated and optimized. Finally, the surface quality is further improved by an optimized thermal post-processing. The roughness of the ridges were analysed with confocal microscopy and the scattering losses were measured at an optical characterization wavelength of 632.8 nm by using the end-fire coupling method. In these investigations the index barrier was formed by multi-energy low dose oxygen ion implantation technology in a depth of 2.7 μm. With optimized laser processing parameters and thermal post-processing a scattering loss as low as 0.1 dB/cm has been demonstrated.

2.6 μm to 12 μm tunable ZGP parametric master oscillator power amplifier

We present a widely tunable mid infrared coherent light source based on a tandem optical parametric oscillator (OPO) and subsequent optical parametric amplification (OPA). The output wavelengths can be seamlessly tuned in the Mid-IR from 2.6 μm to 12 μm or 4000 cm-1 to 833 cm-1 respectively. Maximal output energy of 26 mJ was obtained at a wavelength of 4.25 μm.