ABSTRACT
In recent years, additive manufacturing has been evolving towards flexible substrates for the fabrication of printable electronic devices and circuits. Generally polymer-based, these emerging substrates suffer from their heat sensitivity and low glass-transition temperatures. As such they require new highly-localized sintering processes to treat the electronic inks without damaging the polymer-based substrate. Laser-based sintering techniques have shown great promises to achieve high-quality sintering locally, while controlling the heat penetration to preserve the polymer substrates integrity. In this report, we explore new optimization pathways for dynamic laser-based sintering of conductive silver inks. Multiple passes of a pulsed laser are first performed while varying pulse train frequencies and pulse energies as an attempt to optimize the properties of the silver inks. Then, time-domain pulse shaping is performed to alter the properties of the conductive inks. Together, these pathways allow for the careful control of the time-domain laser energy distribution in order to achieve the best electronic performances while preserving the substrate's integrity. Sheet resistance values as low as 0.024Ω/â¡ are achieved, which is comparable to conventional 1-hour oven annealing, with the processing time dramatically reduced to the milisecond range. These results are supported by finite element modeling of the laser-induced thermal dynamics.
ABSTRACT
The performance of a diode-pumped Cr:LiSAF laser and its intracavity frequency-doubled operation is reported. Close to 1 W of quasi-cw power at 870 nm was obtained in multimode operation. Power in excess of 20-mW cw of TEM(00) second-harmonic power at 435 nm has also been obtained by using a lithium triborate crystal with an infrared-to-visible conversion efficiency of 33%. This result is believed to be the highest yet reported for a true cw blue output from a diode-pumped Cr:LiSAF system. However, the maximum attainable output power was limited by thermal fluorescence quenching. The effect of the pump size on the temperature rise and on the small-signal gain is investigated.
ABSTRACT
A new definition of the pointing stability of a laser beam is proposed. It is derived from the superposition integral between the optical field and a misaligned version of itself. This approach permits the characterization of the pointing stability with a single number, while taking into account the intensity and phase features of the beam. This pointing stability criterion is invariant under propagation and can be related to the moment definitions of beam size, divergence, and quality. The definition is also suggestive of an experimental measurement procedure.
ABSTRACT
Real time holographic recording has been performed in glycerol using CO(2) laser beams for the writing. The dynamics of the grating formation was monitored with a reading beam at 632.8 nm. Particular attention has been paid on temporal behavior.
ABSTRACT
The effects of the substrate temperature (T(s)) on the optical constants of as-deposited Se and SeGe thin films and on the holographic recording properties of these films were investigated. The substrate temperature held between 35 degrees C and 50 degrees C during thin film deposition was identified as an appropriate means to improve the optical recording properties of these films.
ABSTRACT
Phase-conjugate reflectivity obtained by degenerate four-wave mixing are measured in different azo dye solutions. A reflectivity up to 80% was achieved. Values of the nonlinear susceptibility chi((3)) are calculated, and its origin is discussed.
ABSTRACT
Thin films of Se(x)Ge(1-x) have been used as optical recording media for x values of 0.33, 0.5, and 0.67. An investigation of the effect of hydrogen implantation into thin films of this material on optical recording parameters has been performed in the range from 10(14) to 10(16) ions/cm(2). Parameters such as writing energy and contrast ratio were mainly studied. Pulsed holography was also achieved.
ABSTRACT
Changes in the beam profile of the CO2 laser 10R(26) line, caused by transmission through, and absorption by, CDF3 were studied using an array of pyroelectric detectors. During the propagation of the laser beam through CDF3, nonlinear absorption and self-defocusing of the beam have both been determined from measurements of the effect on the exit beam of fluence, radiant energy, CDF3 pressure, transmission cell length, and distance from the exit of the cell to the detector array.
ABSTRACT
We point out the importance of intensity-dependent refractive-index effects when measuring transmission or absorption characteristics of gases with high-power TEA CO(2) laser pulses. An example is given showing how self-focusing in low-pressure SF(6) gas severely affected the transmission of a Gaussian beam. This effect increased rapidly with pressure but remained unchanged when the TEA CO(2) fluence varied from 0.3 to 1.0 J/cm(2).
