English

Application of Multipurpose Femtosecond Laser Interferometry in High Precision Silicon Nanostructures

167
2024-07-10 11:47:35
See translation

Researchers from the Laser Processing Group of the IO-CSIC Institute of Optics in Spain report on the application of multi-purpose femtosecond laser interference in high-precision silicon nanostructures. The related research was published in Optics&Laser Technology with the title "Versatile femtosecond laser interference pattern applied to high precision nanostructured of silicon".


Highlights:
1. A novel fs laser nanostructure configuration based on commercial Ti: Sa fs lasers.
2. A grating and spot array with a manufacturing cycle adjustable to 650 nanometers.
3. Produce amorphous stripes and spots with characteristic sizes as small as 120 nm in silicon.
4. High stripe contrast and clear local flux.
5. Suitable for various materials and applications.

Researchers have introduced a high-precision nanostructure technology based on commercial Ti: Sa femtosecond amplified laser (800 nm, 120 fs, 1 kHz, 1 mJ) beam interference. By applying this technology to the nanostructure of silicon, its potential and versatility have been demonstrated. By utilizing commercial and specialized laser manufactured diffractive optical elements as well as standard optical elements, periodic line gratings and spot arrays with adjustable periods (as low as 650 nm) can be easily manufactured. In addition, the process of manufacturing millimeter level diffraction gratings at a processing speed of up to 0.5 mm/s through multi pulse irradiation was also demonstrated. The various structures written in crystalline silicon have amorphous stripes and spots with a width as low as 300 nm. The corresponding complex morphology profiles include surface protrusions and depressions, with a minimum size of up to 120 nm, which can be controlled by laser flux and stripe width, indicating the existence of multiple competing material recombination processes in the molten phase. The special high contrast of stripe intensity and the near Gaussian intensity envelope of laser spot enable it to be patterned with well-defined local flux, paving the way for the study of single pulse flux dependence. This technology can obtain high-quality experimental data, which is crucial for modeling attempts aimed at revealing the basic formation mechanisms of complex surface morphologies of various materials. In addition, the technology introduced in this article has outstanding potential in the rapid and versatile manufacturing of high-precision metasurfaces.

Figure 1. Experimental setup for femtosecond direct laser interference patterning (DLIP) of nanostructures and intensity distribution on the sample plane recorded in the experiment.

Figure 2. A series of single pulse irradiation with increasing pulse energy were conducted in Si (111), ranging from below the amorphization threshold to 2-3 times the ablation threshold.

Figure 3: Optical micrograph and large-area AFM scan, covering the entire local flux window from below the amorphization threshold to above the ablation threshold.

Figure 4. Imprinted pattern with two cycles of 50 μ m rotated 90 ° and magnification of 20x.

Figure 5. Figure 7 (a) shows an optical micrograph of an area of the pattern recorded through transmission. The diameter of the ablation (transmission) area d ≈ 30 µ m can be easily adjusted through pulse flux and objective lens. b) Optical micrographs of single pulse laser imprinted areas in silicon (111) using laser-generated masks and Mag=20x. The image contrast is set to [0.91, 1.17]. (c) Same as (b), but after the sample moved halfway between the nanodots in both directions, a second irradiation pulse appeared on the pattern.

Figure 6. (a) shows the result of writing a 5 mmx5 mm grating at a speed of v=0.5 mm/s, where the light diffracts into rainbow colors under white light irradiation. Observing under an optical microscope (Figure 8 (b)), it can be observed that the entire grating area extends with highly periodic uniform lines.

Figure 7. Researchers wrote several 5 x 5 millimeter gratings under ablation conditions to explore the effects of laser flux, scanning speed, and grating period. The figure shows the results of gratings A1, A2, and A3.

The fs-DLIP system introduced in this article has strong versatility and can manufacture user selectable nanogrids with periods as low as 650 nm and nanodots with diameters less than 300 nm, and can be extended to large areas through sample scanning. Using the same device to manufacture diffractive optical elements and generate user designed interference patterns provides greater flexibility. In addition, using Ti: Sa fs amplification laser as the light source for fs-DLIP device has several advantages compared to more complex systems used in other works. Firstly, its commercial availability allows for wider deployment. Secondly, it has a higher repetition rate and can achieve higher processing throughput. Thirdly, due to the fewer stages of amplification/nonlinearity, the stability between pulses is relatively high. Fourthly, its Gaussian beam envelope can perform high-resolution imprinting on nanostructures with a clearly defined local flux, paving the way for the study of single pulse flux dependence.

Regarding the specific results of silicon patterning, high-precision amorphous and ablative nanostructures with very sharp boundaries have been obtained. In the amorphous state, the lateral morphology of the stripes is closely related to their width, indicating the existence of different non ablative material recombination processes in the molten phase, including Marangoni convection and surface capillary convection. The versatility of this technology in adjustable stripe period and width is expected to provide high-precision experimental data for studying the underlying mechanisms of complex surface morphology, which is not only applicable to silicon but also to various other materials. In addition, advanced and reliable control of this technology brings broad prospects for manufacturing metasurface based devices.

Source: Yangtze River Delta Laser Alliance

Related Recommendations
  • Trotec Lasersysteme Darmstadt Laser Cutting Technology Center opens

    Trotec Laser, a manufacturer of laser technology in Upper Austria, is opening a new laser cutting competence center. The expanded showroom in Darmstadt now also houses three new large format laser cutters from the SP series. This strategic move is designed to meet the growing demand for large format laser cutting solutions.To celebrate the reopening of the Darmstadt Competence Centre, Trotec will ...

    2023-09-06
    See translation
  • Vast's Haven-1 program has become the world's first commercial space station equipped with SpaceX Starlink lasers

    Vast's Haven-1 program will become the world's first commercial space station, equipped with SpaceX's Starlink laser terminal, providing connections to its crew users, internal payload racks, external cameras, and instruments at speeds of gigabits per second and low latency.Max Haot, CEO of Vast, said: "If you need to provide high-speed, low latency, and continuous Internet connection on the orbit...

    2024-04-10
    See translation
  • Laser technology reveals hidden gases in complex mixtures

    Laser Network reported on January 11th that modern equipment has been fine tuned to detect highly specific gases, including trace gases found in the atmosphere, gases present in combustion exhaust emissions, and gases used in technology plasma applications.They achieve this by calculating the percentage of light at a certain wavelength that is absorbed or attenuated by the sample. This way, the co...

    2024-01-11
    See translation
  • Researchers have implemented a creative approach to reduce stray light using spatial locking technology based on periodic shadows

    Reducing stray light is one of the main challenges in combustion experiments using laser beams (such as Raman spectroscopy) for detection. By using a combination of ultrafast laser pulses and gated ICCD or emICCD cameras, a time filter can be effectively used to remove bright and constant flame backgrounds. When the signal reaches the detector, these cameras can open electronic shutters within the...

    2023-10-16
    See translation
  • IPG Photonics has unveiled a new dual-beam laser with single-mode core power at the Novi Battery Show in Michigan

    IPG Photonics Corporation, a global leader in fiber laser technology, will highlight new and innovative laser solutions at the Battery Show from September 12 to 14, 2023 in Novi, Michigan, USA.The IPG booth will include industry-leading fiber laser sources and automated laser systems for electric vehicle battery welding applications.New laser technology pushes the limits of battery welding speedTo...

    2023-09-12
    See translation