We report on ablation experiments of sputter deposited thin film systems of NiCr and Al2O3 for the fabrication of strain
sensors. To ensure proper functionality of the electrical circuits, the metal film has to be selectively removed while
damage in the Al2O3 films has to be avoided. Damage thresholds of the Al2O3 layer are investigated and damage
mechanisms are discussed. Damage thresholds decrease with increasing number of scans until reaching a constant value.
The processing window defined as the ratio of Al2O3 damage threshold and NiCr ablation threshold increases with
increasing film thickness and number of scans.
This paper presents results of ablation experiments of NiCr layers with thicknesses ranging from 23nm to 246nm on
Al2O3 substrates. Investigated parameters are fluence, number of pulses, film thickness and substrate roughness. The
influence of the parameters on the removal threshold is analyzed in order to identify stable processing parameters.
Patterned NiCr thin films as an essential component for the measurement of mechanical stress are required for the
development of sputtered thin film strain gages. With this new approach strain sensors will be resistant against creeping
or swelling through changing ambient conditions unlike conventional strain gages.
Radial and azimuthal polarizations have attracted new interest in the process development community due to improved
beam propagation and absorption conditions in the ablation cavity. This paper presents our recent activities and results
on polarization converted ultrashort laser pulses by use of segmented half-wave-plates for the generation of ripple
structures with predetermined sub-patterns. The formation of ripples fabricated in metals, ceramics, and semiconductors
is analyzed by the morphological investigation of the structures (spacing and orientation) as a function of the polarization
state of the laser beam.
Laser double pulses offer interesting opportunities to increase the ablation performance of ultra short laser pulses. In
recent published and performed experiments we have presented an optical setup that covers delay times from some
picosecond up to 20 ns as well as first experimental results of ablating aluminium and silicon. In this paper we present
further results of especially interesting time domains for both materials. The ablation efficiency on silicon with inter
pulse delays from 6.3 ns to 15 ns was investigated. In this range the double pulse effect was mainly depending on the
fluency. The double pulse efficiency increase is connected with a higher thermal impact on the work piece. The change
of delay and repetition rate has no influence on the ablation efficiency for both single and double pulses. The
experiments on aluminium concentrated on the pulse delays of 50 ps to 400 ps. The ablation depth per pulse is lower
than for single pulse ablation in this range. Double pulse efficiency decreases up to a pulse delay of 150 ps.
The high demand for beam shaping technology by the display industry has lead to higher resolutions, smaller pixel pitch
and reduced costs. Nowadays high quality, nematic Liquid Crystal on Silicon microdisplays (LCoS) with resolutions of
1920 × 1080 pixels and 8 μm pixel pitch are available. The optical properties of these microdisplays allow for their
application as an adaptive optical element where instantaneous change between arbitrary beam profiles is necessary.
Laser material processing which often requires high beam qualities with various beam profiles is one industry where this
technology could be applied. In this paper, a compact beam shaping setup and simple characterization methods for
practical use of the LCoS at micromachining stations are presented.
Utilisation of ultrashort laser pulses enables high precision in laser micromachining processes. Due to low thermal interaction between laser beam and matter, the vicinity of the laser ablation is free from melt and heat influenced zones. Established laser microstructuring processes on basis of femtosecond laser pulses have been applied for manipulation of micromechanical components of Silicon-gyrometers that are manufactured for the automotive industry. Compensation of mechanical imbalance, and adjustment of resonance frequencies have been successfully performed by mass balancing, and manipulation of the spring elements' geometries by laser ablation with a lateral resolution of 10-20 μm, and a vertical resolution of 500 nm-4 μm. The approach for automated laser processing on wafer-level is demonstrated.
Results of ablation of different materials by femtosecond and picosecond laser pulses are compared. Advantages and disadvantages of both laser systems are discussed. Two most important criteria, processing speed and quality of the fabricated structures, are addressed. High repetition rate picosecond lasers allow high speed cutting of thin metal foils and silicon wafers, whereas for micro-drilling it is more advantageous to use femtosecond laser systems.