Project: Ytterbium-doped Alignment-free Femtosecond Fiber Laser Engineering

Background information:_x000D__x000D_Near IR multi-µJ 100–200-fs are ideally suited for a broad scope of photonic industrial, research, biomedical and security applications. Prominent examples are laser photorefractive keratomy in ophthalmology, precision micromachining of hard materials (e.g. sapphire) and 3-D waveguide writing in photoelectronics, surface nano-patterning in tribology, bio-sensing with wavelength-tunable or fixed broadband pulses (e.g. using the CARS technique). These and other potential applications open a lucrative market for hundreds of such laser sources per annum. The estimated global demand for lasers in vision correction is 5000 units. In 2007 several ground-breaking long-term contracts were signed between electronics and medical industries and laser manufacturers. Industrial interest in ultrafast lasers is perhaps best exemplified by a massive order put by Carl Zeiss Meditec to IMRA America for the delivery of µJ fs fiber amplifiers for keratomy despite the limited output pulse energy. For the obvious reasons of durability, practicality, environmental stability and the ability to rely on rugged telecom-grade components, fiber laser technology, including fiber chirped pulse amplifiers (FCPA) is booming. Recently the group of Limpert and Tünnermann has demonstrated fs pulse amplification at 1 kW output power level. Backed by a sizable US military contract, in 2006 Clark MXR released a 20-W 2-MHz 10-µJ fs laser. Although such results are extremely impressive, all known FCPA systems exhibit fundamental bottlenecks: poor recompressed quality and long (0.5-1 ps) pulse duration if splicable fiber Bragg gratings are used to stretch the pulse before the amplifier and/or poor mechanical stability if a conventional diffraction grating stretcher is used and the pulse is relaunched into the gain fiber._x000D__x000D_Project goals:_x000D__x000D_Project YAFFLE— named after the commonest European green woodpecker known, despite its modest size, for its agility and strength— aims to develop a monolithic <200-fs >15-µJ FCPA system that would overcome current technology barriers and present an attractive hands-free ultrafast laser source for industrial use. The solutions to the current technological challenges will be introduced along several tracks: a) design of a broadband air-gap-free, polarization stable fiber ring nJ seed laser based on the novel similariton mode-locking technique; b) design of a novel all-fiber pulse stretcher for direct delivery of the seed pulse into the amplifier fiber core. Using the latest advances in the design and fabrication of photonic crystal fibers (PCF), the stretcher should provide high-order dispersion correction at minimum added nonlinear pulse distortions; c) the most critical final power amplifier stage will be pumped and seeded from the input side only using a recently developed tapered fiber bundle (TFB) technology and combine the pump power from 6-8 low-power air-cooled laser diodes. In addition, special mode filtering techniques will be employed in the final amplifier stage to ensure large mode operation on the one hand and high tolerance to bending losses, needed for achieving amplifier compactness, on the other._x000D__x000D_Crucially for system reliability, in the envisaged FCPA architecture,— so far never attempted for the target pulse energy and duration,— all free space gaps between the fibers in the amplifier chain, including diode pump delivery lines, will be eliminated. Furthermore, if the progress in large-aperture volume Bragg gratings (VBG) retains its current pace, at the final stage of YAFFLE it would even become possible to replace the air-spaced grism compressor at the output of the FCPA with a VBG glass slab._x000D__x000D_Beside the outlined pure laser source development, the YAFFLE consortium will also conduct research in the area of pivotal potential applications, especially those that can underscore the potential of the new laser source in nonlinear optical applications, such as energetic supercontinuum generation and frequency comb extension, generation of parametrically tunable pulses and time-resolves spectroscopic applications; microchannel and microwaveguide fabrication in quartz and other transparent optical materials using multiphoton absorption._x000D__x000D_Consortium:_x000D_The YAFFLE consortium is formed around an industrial P, Menlo GmbH, the world leader and pioneer in optical frequency comb sources for metrology. The company, that started its activity as a spin-off of the research group headed by the Nobel Prize winner T. Hänsch, retains strong research ties to the renowned Max-Planck Institute for Quantum Optics (MPQ) and continues to hold a scientific and technological edge. The international research P in the consortium is Photonics Institute of TU Vienna which enjoys a long-standing cooperation with MPQ and Menlo. The Ps have complementary expertise in source development and ruggedization and present an optimum balance of know-how to meet the challenges of the project.

Acronym	YAFFLE (Reference Number: 4319)
Duration	01/01/2009 - 31/03/2012
Project Topic	We propose to develop a versatile ultracompact environmentally stable monolithic Yb-doped fiber laser system delivering >15-µJ <200-fs pulses at repetition rates up to 1 MHz for biomedical and chemical applications, and material processing (rapid prototyping, micromachining, micro-structuring.)
Project Results (after finalisation)	The CO result is a laser system able to deliver energetic 5-µJ pulses at a center wavelength of 1053 nm, which is primarily orientated at industrial micromachining applications. It provides technological advantages over established solid-state laser focussed contenders and can compete against the US based companies, which deliver alternative FCPA systems. White light generation was demonstrated within the project and example experiments in micro-material processing were performed.
Network	Eurostars
Call	Eurostars Cut-Off 1

Project partner

Number	Name	Role	Country
2	Menlo Systems GmbH	Coordinator	Germany
2	Photonics Institute, Vienna University of Technology	Partner	Austria