English

Application of Multipurpose Femtosecond Laser Interferometry in High Precision Silicon Nanostructures

92
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
  • Deep Photon Network Platform, Empowering Any Functional Photon Integrated Circuit

    The widespread application in the fields of optical communication, computing, and sensing continues to drive the growing demand for high-performance integrated photonic components. Recently, Ali Najjar Amiri of Kochi University in Türkiye and other scholars proposed a highly scalable and highly flexible deep photonic network platform, which is used to realize optical systems on chip with arbi...

    2024-03-11
    See translation
  • Entangled photon pairs generated by quantum light sources can be used for quantum computing and cryptography

    A new device composed of semiconductor rings generates pairs of entangled photons, which can be used in photon quantum processors.Quantum light sources generate entangled photon pairs, which can be used in quantum computing and cryptography. A new experiment has demonstrated a quantum light source made from semiconductor gallium nitride. This material provides a multifunctional platform for devic...

    2024-03-30
    See translation
  • US blue laser company Nuburu plans to raise nearly $65 million in funding

    Recently, Nuburu, a high-power industrial blue light laser company in the United States, announced that the company has agreed to a new financing arrangement worth up to $65 million.This agreement was reached between Nuburu and the Delaware hedge fund Liquous LP, which claims to provide a "customized liquidity solution". According to the terms of the agreement, Nuburu will first receive an initial...

    2024-10-11
    See translation
  • The world's highest power industrial grade fiber laser is released in Tianjin

    On August 31st, Tianjin Kaipulin Optoelectronics Technology Co., Ltd. (hereinafter referred to as Kaipulin), a Tianjin Port Free Trade Zone enterprise, officially released the world's first 200000 watt ultra-high power industrial grade fiber laser, breaking the record for the highest power of industrial grade fiber lasers in the world and marking China's stable position in the international advanc...

    2024-09-02
    See translation
  • Dr. Torsten Derr will be appointed as the CEO of SCHOTT Group on January 1, 2025

    November 25, 2024, Mainz, GermanyStarting from January 1, 2025, Dr. Torsten Derr will take over as the CEO of SCHOTT Group.The new CEO of SCHOTT Group previously served as the CEO of SGL Carbon SE.Starting from January 1, 2025, Dr. Torsten Derr will officially assume the position of CEO of SCHOTT Group. SCHOTT Group announced in October 2024 that Dr. Torsten Derr will succeed Dr. Frank Heinrich, w...

    2024-11-27
    See translation