Laser scribing is an indispensable step in the industrial production of Cu(In,Ga)Se<sub>2</sub> thin film solar modules. While cell separation (P1 and P3) is usually achieved using high velocity, low overlap lift-off processes, removal of the absorber layer for generating an electrical back-to-front interconnect (P2) is typically a slow process. In the present study we present an approach for scaling the classical P2 process velocity to an industrially exploitable level. We demonstrated successful P2 scribing at up to 1.7 m/s in a single beam, single pass configuration using a linear focal spot. The presented process is robust against variations in the scribing velocity and focal position, a key point for successful machine integration.
The thin-film solar cell market has seen a period of consolidation during the last years and many involved companies
were forced to stop production due to increasing price pressure from competing cell technologies. Today, thin-film solar
industry is gaining momentum again. Especially Cu(In,Ga)Se2 technology evolves at high pace fired by recently achieved
record efficiencies of 20.4 percent on flexible polyimide substrate  and 20.8 percent on glass substrate . Fresh
companies are preparing market entry with matured products and manufacturing technology suitable for high-volume
and high-throughput production. Among these key-enabling technologies is laser patterning for cell-to-cell
interconnects. Several research groups worked on efficient and reliable laser processes that are now ready for the
industrial assessment. Here we present a set of work-horse processes for P1, P2 and P3 scribing of CIGS cells on glass
substrate. Optimized parameters are presented for 532 nm and 1064 nm using 50 ps pulses from an all-in-fiber laser
system. We further demonstrate the successful realization of functional 8-cell modules with a reduced “dead-zone”
width of 70±5 μm and high efficiencies. The certified efficiency of 16.6 percent for our low-dead-zone champion module
confirms the observation that shrinking of interconnects has no adverse effects on their electrical quality.
We have successfully demonstrated white-light continuum (WLC) generation in the near-infrared (NIR) region from 1.1 μm to 2.5 μm using specially designed highly nonlinear optical fibers. A passively mode-locked diode-pumped Er:Yb:glass laser with a semiconductor saturable-absorber mirror (SESAM) successfully generates femtosecond pulses with about 90 mW average output power, which is sufficient to produce the WLC with over 40 mW power without any additional optical amplification. This WLC source is expected to be suitable for many applications, such as laser radar systems and optical gas sensing.
Fast pulse-generating laser sources at 10 GHz are commercially available. For future communications system applications of these light sources at 40 GHz, we developed a passive, fully integrated optical 10 to 40 GHz time-domain multiplexer. This device is very compact (16×5 mm<sup>2</sup>) and robust, whereby its miniaturization and robustness are based on the high-index-contrast silicon-oxynitride (SiON) waveguide technology used. This 4X multiplexer consists of two cascaded asymmetric Mach-Zehnder structures. Thereby a total of three directional couplers and two delay lines of 50 ps and 25 ps, respectively, are cascaded. Because of the high SiO2-SiON index contrast of 3.8 % it was possible to realize a multiplexer device with bending radii of less than 1.0 mm in an ultra-compact double-folded design. The slightly unbalanced attenuation in the delay lines was pre-compensated by the directional coupler design, i.e. by detuning from 50 % : 50 % coupling ratio. We demonstrated experimentally that with a fundamentally mode-locked 10 GHz Er:Yb:glass laser source at the design wavelength of 1535 nm our 4X multiplexer produces a 40 GHz pulse train with < 0.22 dB pulse-to-pulse power variation and < 350 fs timing jitter. Although the current device is designed for 40 GHz, its principle can be applied to 160 GHz or higher, provided that suitable pulse sources are available.
Femtosecond and picosecond pulses can find many applications if they can be produced with laser sources that are not only powerful and efficient but also compact and reliable. In continuous wave operation, diode pumping of solid-state lasers has allowed for a rapid progress towards powerful, compact and reliable sources, while the often used technique of Kerr lens modelocking for pulsed operation tends to be in conflict with requirements for diode-pumpable high power designs. Passive modelocking with semiconductor saturable absorber mirrors solves this problem as it relaxes the restrictions on the cavity design. We report on our recent achievements in this field. In particular we present a novel semiconductor device for dispersion compensation and various improved diode-pumped passively modelocked lasers. Also we show which laser parameters determine the stability of a passively modelocked lasers against Q-switching instabilities.