Ultrafast 2.1µm Holmium Lasers for GHz ablation

Project Information

Giga2u

Grant agreement ID: 101138967

DOI

10.3030/101138967

Project closed

EC signature date 21 September 2023

Start date 1 October 2023

End date 31 March 2025

Funded under

• European Research Council (ERC)

Total cost

No data

EU contribution

€ 150 000,00

Coordinated by

RUHR-UNIVERSITAET BOCHUM
Germany

Periodic Reporting for period 1 - Giga2u (Ultrafast 2.1µm Holmium Lasers for GHz ablation)

Reporting period: 2023-10-01 to 2025-03-31

Summary of the context and overall objectives of the project

Femtosecond (fs) lasers are ubiquitous tools in science and industry, their widespread applications aided by their increasingly wide commercial availability. One of the fastest growing markets for ultrafast lasers is in material processing with approximately 16.7 - 22.0 billion € (2022) and a growth annual rate of 7.7 - 10.0% expected in coming years. Most commercial femtosecond lasers for material processing, operate at around 1 μm wavelength and are in the category of high-cost laser systems. Therefore, advancements in laser technology that allow to increase the ablation speed and efficiency at minimal investment are key potential new market players. In this regard, the recently acclaimed ablation-cooling regime using GHz repetition rate bursts of femtosecond pulses, has shown to outperform traditional ablation speeds and has further potential to reduce the cost of the laser system: however, an aspect of this disruptive technology that has not been thoroughly studied in terms of market potential is the operation wavelength. In this regard, the 2-3 μm wavelength window (or so called short-wave infrared region (SWIR) region), has shown significant evidence that prominent materials such as glasses, polymers and water-rich tissue are expected to have a significantly reduced threshold single-pulse energy needed. Effectively, this means even cheaper laser systems can be used, which would be disruptive for the industry. However, GHz repetition rate fs-lasers in the SWIR region remain extremely rare, therefore the possibilities open by SWIR GHz ablation remain unexplored. The objective of this project is to develop suitable laser technology and explore the application and market potential for SWIR GHz ablation of glass.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

The main technical and scientific outcomes of our proof of concept project were:
1) the demonstration of a watt-level GHz repetition rate, modelocked Holmium femtosecond oscillator with sub-100 fs at 2.1 um wavelength. The laser system was based on the very broadband new Holmium material, Ho:CALGO for achieving short pulse duration and high-power simultaneously - which was so far not possible with Holmium. This resulted in a publication to the scientific community which continues to gain attention.
2) the demonstration of a 10 W regenerative amplifier in the kHz repetition rate regime with 100 uJ pulse energy and sub-ps duration. This system has attracted a lot of attention in the community, since normally Holmium lasers are difficult to operate with high gain and sub-ps. This was possible due to the unusually high bandwidth of Ho:CALGO.
3) first tests of ablation in glasses and silicon using the kHz amplifier from 2)

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

The proof of concept project and technical outcomes described above supported the main impactful outcome of this project which was the recent founding of a spinoff company called Rayven, that aims to exploit 2.1 um femtosecond technology for the material processing market.

A large part of the project was dedicate to explore the business opportunities of GHz ablation at this longer wavelength. The main finding of this exploration was that the GHz technology is still in a too early adoption stage at other more traditional wavelengths around 1 um to consider directly penetrating the market at this new wavelength. In fact, potential customers were significantly more interested in a laser system at 2.1um but with "traditional" high energy pulses - which explained the slight deviation in the technical realization from the originally planned development of a multi-pass amplifier to rather focus on single-pulse energy first. We also note that we have nevertheless developed the key know-how in seed lasers and amplification to then quickly adapt our product when the market is ready.

As part of this project, an engineering platform was also developed for the technology. The entire laser platform was developed in a modular and practical way to adapt to parameters required by the customers. Furthermore, risks in the supplier chain were identified. Alternative technologies were identified to mitigate risks, in particular in the supply of the unique laser crystals that support the performance of the laser.

During the project, we submitted a patent application for a new implementation of an amplifier geometry that could support future technology developments.

In the future, two more research aspects need to be tackled to fully understand the future market when moving to GHz ablation 1) Adapting the existing amplifier technology (point 2 above) to amplify GHz bursts. During the project we started simulations that show that maintaining clean flat-top bursts during amplification containing many pulses >>10 is challenging; therefore pulse shaping using modulators need to be implemented 2) measurements of the processed glass samples showing advantages of 2.1 um compared to 1 um in GHz regime.