Ultrafast 2.1µm Holmium Lasers for GHz ablation

Projektinformationen

Giga2u

ID Finanzhilfevereinbarung: 101138967

DOI

10.3030/101138967

Projekt abgeschlossen

EK-Unterschriftsdatum 21 September 2023

Startdatum 1 Oktober 2023

Enddatum 31 März 2025

Finanziert unter

• European Research Council (ERC)

Gesamtkosten

Keine Daten

EU-Beitrag

€ 150 000,00

Koordiniert durch

RUHR-UNIVERSITAET BOCHUM
Germany

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

Berichtszeitraum: 2023-10-01 bis 2025-03-31

Zusammenfassung vom Kontext und den Gesamtzielen des Projekts

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.

Arbeit, die ab Beginn des Projekts bis zum Ende des durch den Bericht erfassten Berichtszeitraums geleistet wurde, und die wichtigsten bis dahin erzielten Ergebnisse

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)

Fortschritte, die über den aktuellen Stand der Technik hinausgehen und voraussichtliche potenzielle Auswirkungen (einschließlich der bis dato erzielten sozioökonomischen Auswirkungen und weiter gefassten gesellschaftlichen Auswirkungen des Projekts)

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.