Silicon nanoparticles are of interest for their optical properties, for example, in light scattering. Here, Zywietz et al. achieve the laser printing of silicon nanoparticles on a substrate at predefined positions, and with control over their crystalline phase.

/pdf/laser-printing-of-silicon-nanoparticles-with-resonant-34kjpdes1w.pdf

Laser printing of silicon nanoparticles with resonant optical electric and magnetic responses

Methods of Experimental Physics.

It is an object of the present invention to provide a laser irradiation apparatus which can form a linear beam spot with a short optical path length, form a linear beam spot being long in a long-side direction, and reduce displacement of a condensing point at opposite ends in a direction of its line. In a laser irradiation apparatus having an optical system for shaping a laser beam emitted from a laser oscillator into a linear beam spot having a long-side direction and a short-side direction, the optical system includes a long-side direction condensing cylindrical lens disposed between a first short-side direction condensing cylindrical lens and a second short-side direction condensing cylindrical lens. Displacement of a position of a homogeneous plane is generated by the long-side direction condensing cylindrical lens so that a distance from the homogeneous plane to the second short-side direction condensing cylindrical lens is constant not depending on a field angle.

Laser irradiation apparatus, laser irradiation method and method for manufacturing semiconductor device

We demonstrate a nanoscale, subpicosecond (ps) metamaterial device capable of terabit/second all-optical communication in the near-IR. The 600 fs response, 2 orders of magnitude faster than previously reported, is achieved by accessing a previously unused regime of high-injection level, subpicosecond carrier dynamics in the α-Si dielectric layer of the metamaterial. Further, we utilize a previously unrecognized, higher-order, shorter-wavelength negative-index resonance in the fishnet structure, thereby extending device functionality (via structural tuning of device dimensions) over 1.0−2.0 μm. The pump energy required to modulate a single bit is only 3 nJ over our current 700 μm2 area device and can be easily scaled into the picoJoule regime with smaller cross sectional areas.

/pdf/subpicosecond-optical-switching-with-a-negative-index-3lq4iyszpm.pdf

Subpicosecond optical switching with a negative index metamaterial.

It is an object to achieve continuous crystal growth without optical interference using a compact laser irradiation apparatus. A megahertz laser beam is split and combined to crystallize a semiconductor film. At this point of time, an optical path difference is provided between the split beams to reduce optical interference. The optical path difference is set to have a length equivalent to the pulse width of the megahertz laser beam or more and less than a length equivalent to the pulse repetition interval; thus, optical interference can be suppressed with a very short optical path difference. Therefore, laser beams can be applied continuously and efficiently without energy deterioration.

Method for manufacturing semiconductor device and laser irradiation apparatus

Ultrashort pulsed laser irradiation is used to crystallize 100-nm amorphous-silicon (a-Si) films. The crystallization process is ob- served by time-resolved pump-and-probe reflection imaging in the range of 0.2 ps to 100 ns. The in-situ images, in conjunction with postpro- cessed scanning electron microscopy (SEM) and atomic force micros- copy (AFM) mapping of the crystallized structure, provide evidence for nonthermal ultra-fast phase transition and subsequent surface-initiated crystallization. © 2003 Society of Photo-Optical Instrumentation Engineers.

http://www.dmphotonics.com/Ultrafast_laser-induced_crystallization_of_amorphous_silicon_films/Ultrafast%20laser-induced%20crystallization%20of%20amorphous%20silicon%20films.pdf

Ultrafast laser-induced crystallization of amorphous silicon films

Ultra-short pulsed laser irradiation was used to crystallize an a-Si film with a laser fluence of 0.12 J/cm2. The crystallization process was observed by time-resolved pump- and-probe imaging in the range of 0.2 ps to 100 ns. Reflectivity data along with post-processed SEM pictures provide evidence for a non-thermal ultra-fast solid-phase transition. A crystallization sequence based on atomic self- diffusion is suggested.

Melting and solidification of a silicon film by continuous wave laser beam irradiation has been studied. The silicon film melting and recrystallization is controlled by the temperature distribution in the semiconductor. Calculations have been carried out for a range of laser beam parameters and material translational speeds. The temperature field development also has been monitored with localized transient reflectivity measurements. During transient heating of semitransparent materials at the nanosecond scale, the thermal gradients across the heat affected zone are accompanied by changes in the material complex refractive index. These changes, coupled with wave interference, modify the energy absorption and thus the temperature field in the target material. These affects are taken into account in a rigorous manner using thin film optics theory.

Heat transfer in laser processing of thin films

Fundamental questions arise regarding the possibility and nature of melting and the ensuring mechanism of ablation in femtosecond laser processing of materials. A comprehensive experimental study is presented to address these issues in depth and detail. The mechanisms of ultra-fast laser-induced phase-transformations during the laser interactions with materials have been investigated by time-resolved pump-and- probe imaging in both vacuum and ambient environment. The temporal delay between the pump and probe pulses is set by a precision translation stage up to about 500 ps and then extended to the nanosecond regime by an optical fiber assembly. Ejection of material in the form of nanoparticles is observed at several picoseconds after the main pulse. The ignition of surface-initiated plasma into the ambient air immediately following the pump pulse and the ejection of ablated material in the picosecond and nanosecond time scales have been proven by high-resolution, ultra-fast shadowgraphy. To further dissect the origin and evolution of the ablation process, a double pulse experiment has been implemented, whereby both the pump and probe pulses are split into two components each separated by variable temporal delays. A diffractive optical element is used to fabricate micro-channels in silicon wafers.

Ultrafast laser-induced processing of materials: fundamentals and applications in micromachining

The formation of bubbles at a liquid-solid interface due to acoustic cavitation depends particularly on the preconditions of the interface. Here, it is shown that following laser- induced bubble formation at the interface the acoustic cavitation efficiency is strongly enhanced. Optical reflectance measurements reveal that this observed enhancement of acoustic cavitation due to preceding laser-induced bubble formation, which could be termed as a memory effect, decays in a few hundred microseconds. By performing a double-pulse experiment using two excimer lasers the influence of process parameters, such as liquid temperature and salt concentration, on the temporal decay of the memory effect has been studied. An analysis of the experimental results by a diffusion model is presented.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

https://kops.uni-konstanz.de/bitstream/handle/123456789/9091/154_procspie_1994.pdf;sequence=1

Constantine P. Grigoropoulos

Papers

Ultrafast laser-induced crystallization of amorphous silicon films

Ultrafast laser-induced crystallization of amorphous silicon films

Heat transfer in laser processing of thin films

Ultrafast laser-induced processing of materials: fundamentals and applications in micromachining

Memory-Effect on Acoustic Cavitation