The Application of Femtosecond Laser in Precision Photonics Manufacturing

Femtosecond laser emits ultra short light pulses with a duration of less than 1 picosecond, reaching the femtosecond domain. The characteristics of femtosecond lasers are extremely short pulse width and high peak intensity.

Ultra short blasting can minimize waste heat, ensure precise material processing, and minimize incidental damage. Their peak intensities can cause nonlinear optical interactions, such as multiphoton ionization and plasma formation, providing precise spatial control of laser energy for various applications.

The nonlinear constraint effect of femtosecond lasers allows for nanoscale resolution, achieving features below the diffraction limit. These lasers have a wide range of applications as they can process various materials, including metals, semiconductors, ceramics, polymers, and composite materials, without the need for masks or photoresists. Their ability to focus on transparent materials also helps to create complex three-dimensional structures, which is crucial for manufacturing integrated photonic chips.

Overall, femtosecond lasers are an ideal choice for precision microfabrication and photonics manufacturing.
Accurate nanoscale control of unit structures and gaps is crucial for effectively controlling light in photonic crystals in the near-infrared and visible light ranges. Femtosecond lasers perform excellently in manufacturing 3D micro/nanostructures directly in transparent materials, utilizing their ultra short pulse duration to achieve excellent accuracy.

A study published in "Light: Science and Applications" demonstrates this by introducing a method for manufacturing photonic crystal structures using nanoscale femtosecond laser multi beam lithography. Researchers focused a controllable multi beam light field inside the crystal and combined it with chemical etching. This method can precisely control the structural units and gaps of sub wavelength size, overcoming the limitations of single beam processing.

The proposed method is cost-effective and simple, and can achieve 3D photonic crystal structures within crystals, with potential applications in optical communication and manipulation.

The advancement of materials science and nanofabrication has led to the exploration of periodic nanostructured surfaces, such as plasma and dielectric metasurfaces, for advanced photonics applications. Traditionally, photolithography methods have been used to process these periodic surface structures, which can be both complex and time-consuming.

However, focusing on femtosecond lasers provides a one-step, maskless, and efficient alternative solution suitable for various materials. This allows for the creation of features smaller than the laser wavelength through laser-induced PSS.

Recent studies, particularly those studying wide bandgap transparent crystals such as LiNbO, have demonstrated the potential of femtosecond lasers in manufacturing large-area LIPSS with enhanced light absorption through controlled heating strategies. This provides a promising approach for the precision manufacturing of dielectric crystals other than LiNbO
Femtosecond laser direct writing provides enormous potential for manufacturing 3D photonic integrated circuits on transparent substrates. However, a key challenge of this technology is to achieve smooth and significant refractive index changes within the laser irradiation area, which hinders the development of compact PICs.

A study published in the journal Science of China and Physics, Mechanics, and Astronomy has solved this problem by proposing a significant method to suppress the bending loss of small curvature radius waveguides, paving the way for miniaturization of 3D photonic integrated circuits.
The proposed method involves the use of femtosecond lasers to directly write multiple modified tracks into fused silica, thereby enhancing the refractive index contrast and successfully reducing the bending loss of bent waveguides. This breakthrough is expected to improve the integration density and flexibility of 3D photonic devices.

Chemical etching after femtosecond laser irradiation utilizes laser-induced changes in chemical properties to selectively etch laser modified areas. This allows complex 3D micro nano structures to be directly written into the interior of dielectric materials. FLICE has been applied to create embedded hollow microstructures for microfluidics and 3D optofluids in glass.

Recent work has achieved over 100000 ultra-high etching selectivity in crystals such as YAG and sapphire. This makes it possible to create nanoscale 3D photonic lattices, waveguides, and nanopores without damaging the crystal.

As a maskless and high-precision 3D processing technology, femtosecond laser processing can perform surface lithography on materials such as thin films of lithium niobate. This breakthrough has successfully overcome the challenges in material integration and enabled the manufacturing of high-performance photonic components.

For example, researchers used femtosecond laser assisted chemical mechanical polishing lithography to create low loss waveguides and high Q microresonators on lithium niobate chips. This processing strategy has strong potential to functionalize different crystal platforms for integrated photonics.

The silicon ablation of femtosecond lasers involves the use of ultra short pulses to accurately remove materials from the silicon substrate. This process is crucial in precision photonics, as it can create complex structures with minimal thermal damage, enabling the manufacture of high-quality optical devices such as optical waveguides.

Researchers at RIKEN Advanced Photonics Center have developed a new technology called BiBurst mode, which uses GHz pulse pulses of femtosecond laser pulses grouped in MHz envelope for efficient and high-quality silicon ablation. These survey results are published in the International Journal of Extreme Manufacturing.

The team has demonstrated that using BiBurst mode can perform silicon ablation at a speed 4.5 times faster than single pulse mode and has excellent quality. This mechanism involves absorbing subsequent pulses at the absorption site generated by the previous pulse, which helps to improve efficiency. This breakthrough may have a significant impact on the basic research and industrial applications of femtosecond laser processing, thereby improving throughput and micro/nano processing accuracy.

Femtosecond laser writing stands out for its low cost, simplicity, and rapid prototyping capabilities, making it suitable for passive and reconfigurable integrated photonic circuits. The rapid reconfigurability of this technology makes it valuable for the initial evaluation of optical laboratories.
A study published in Applied Physics Letters used FLW technology to manufacture programmable dual qubit quantum photon processors. The manufactured FLW quantum processor achieves high fidelity, with a single qubit gate of 99.3% and a double qubit CNOT gate of 94.4%.
Despite challenges such as propagation loss and low refractive index contrast, FLW chips exhibit natural low loss coupling with standard single-mode fibers and have advantages in quantum photon experiments.

Source: Laser Net