Anthony Bertrand

Investigation of CIS/CIGS and CdTe solar cells scribing with high-power fibre short pulse lasers

We present here some of the last results of the EUROPEAN project ALPINE. We present both the development of an adjustable fibre laser pulse source and scribing results on CdTe and CIGS solar cells. The scribing tests were performed at three different pulse durations: 400 fs, 8 ps and 250 ps. The results obtained with 250 ps are already very promising for P3 steps in both CdTe and CIGS solar cells. In both cases the results were validated electrically. In the case of P3 scribing for CIGS solar cells, shunt resistances as high as 125 kΩ.cm were obtained. Isolation resistances were higher than 1 MΩ.cm. The processing speed was 2 m/s.

Optimization of pulsed fiber laser scribing for CdTe and CIGS solar cells

The FP7 EU funded ALPINE project is focused on the processing of new type of thin film CdTe and CIGS photovoltaic modules by means of pulsed fiber laser scribing. The latest results of scribing tests performed for different laser parameters for P1, P2 and P3 steps in both CdTe and CIGS solar cells are discussed showing examples for CdTe module processing.

Adjustable supercontinuum laser source with low coherence length and low timing jitter

This paper introduces a supercontinuum (SC) laser source emitting from 400 nm to beyond 1750 nm, with adjustable pulse repetition rate (from 250 kHz to 1 MHz) and duration (from ~200 ps to ~2 ns). This device makes use of an internally-modulated 1.06 μm semiconductor laser diode as pump source. The output radiation is then amplified through a preamplifier (based on single-mode Yb-doped fibres) followed by a booster (based on a double-clad Yb-doped fibre). The double-clad fibre output is then spliced to an air-silica microstructured optical fibre (MOF). The small core diameter of the double-clad fibre allows reducing the splice loss. The strongly nonlinear propagation regime in the MOF leads to the generation of a SC extending from the violet to the nearinfrared wavelengths. On the Stokes side of the 1.06 μm pump line, i.e., in the anomalous dispersion regime, the spectrum is composed of an incoherent distribution of quasi-solitonic components. Therefore, the SC source is characterised by a low coherence length, which can be tuned by simply modifying pulse duration, that is closely related to the number of quasi-solitonic components brought into play. Finally, the internal modulation of the laser diode permits to achieve excellent temporal stability, both in terms of average power and pulse-to-pulse period.

Exploring new avenues for laser micromachining

There is growing demand in several industrial sectors for instruments with a very high degree of precision, to which lasers offer the ideal solution. For a non-specialist, however, it can be difficult to identify which of the many commercially available lasers best fits their particular needs. Furthermore, the laser is generally integrated as a component in a machine that may comprise (for example) a complex optical path, galvanometric heads, and software. Laser machines are therefore expensive, and the decision to invest in one needs careful consideration. Using lasers for manufacturing has several advantages. First, there is no contact with the material in process, and the laser system enables high accuracy, repeatability, and reproducibility. In addition, lasers offer sufficient flexibility to adapt to the parameters of the material (e.g., metal, polymer, glass, or ceramic). Continuous wave lasers are widely used for joining or direct additive laser construction (CLAD), while pulsed lasers— where thermal effects are directly linked to pulse duration— enable micromachining.1, 2 Figure 1 shows a typical laser setup for engraving. Our collaboration of research centers and universities, known as EcoLaserFact, came together in 2012 to offer practical help to companies considering micromachining laser-based processes for their business development. The collaboration has also developed new processes for laser micro-joining, micro-fluidic devices, surface texturing, CLAD technology, and new milling systems. The group was founded by nine partners based in northwest Europe: Multitel, Sirris, and Cluster Photonics in Belgium; Karlsruhe Institute of Technology and Bayerisches Lazercentrum in Germany; the University of Birmingham and Cardiff University in the UK; and Irepa Laser and the European Photonic Industrial Consortium in France. These companies were later joined by Belgian groups Lasea and the Centre de Recherche de l’Industrie Belge de la Céramique. Figure 1. Typical example of a laser setup for engraving. The galvanometric head translates the laser beam on the workpiece in the X and Y directions. The Z module changes the position of the focal point of the laser beam. HR: High reflector.

High-energy picosecond hybrid fiber/crystal laser for thin films solar cells micromachining

We report on an hybrid fiber/crystal ultra-short pulsed laser delivering high pulse energy and high peak power in the picosecond regime. The laser is composed of a mode-lock fiber oscillator, a pulse picker and subsequent fiber amplifiers. The last stage of the laser is a single pass Nd:YVO4 solid-state amplifier. We believe that this combination of both technologies is a very promising approach for making efficient, compact and low cost lasers compatible with industrial requirements.

Efficient high-power narrow-linewidth all-fibred linearly polarized ytterbium laser source

We report on experimental results on a high power, all-fibred, linearly polarized, mode-locked laser at 1.03 μm. The laser generates pulses of 40 ps wide at a repetition rate of 52 MHz, exhibiting 12 kW peak power. Dispersion in optical fibres is controlled to obtain both high power and narrow spectral linewidth. The average output power reached is 25 W with a spectral linewidth of 380 pm and a near diffraction limit beam (M2 < 1.2). This laser is an ideal candidate for applications like IR spectroscopy, where high peak power and narrow linewidth are required for subsequent wavelength conversion.

All fiber high energy, high power picosecond laser

We report on 83W, 14μJ, 5.9MHz, 30ps MOPA fiber laser based on an Yb modelocked fiber oscillator and a rod-type LMA amplifier. By frequency tripling, this configuration can generate up to 20W of UV.

High repetition rate, high energy, actively Q-switched all-in-fiber laser

We report an actively Q-switched Ytterbium-doped all-in-fibre laser delivering 10ns pulses with high repetition rate (from 100kHz to 1MHz). The laser operation has been validated at three different wavelengths (1040, 1050 and 1064nm). The laser can deliver up to 20Watts average power with an high beam quality (M2 = 1).

Impact of pumping configuration on all-fibered femtosecond chirped pulse amplification

We experimentally compared the co- and counter-propagative pumping scheme for the amplification of ultra-short optical pulses. According to pumping direction we show that optical pulses with a duration of 75 fs and 100mW of average output power can be obtained for co-propagative pumping, while pulse duration is never shorter than 400 fs for the counter-propagative case. We show that the impact of non-linear effects on pulse propagation is different for the two pumping configurations. We assume that Self Phase Modulation (SPM) is the main effect in the copropagative case, whereas the impact of Stimulated Raman Scattering is bigger for the counter-propagative case.