Details of Grant 

EPSRC Reference:	EP/D032954/1
Title:	Regimes of ultrafast laser writing.
Principal Investigator:	Khrushchev, Dr I
Other Investigators:
Researcher Co-Investigators:
Project Partners:
Department:	Sch of Engineering and Applied Science
Organisation:	Aston University
Scheme:	Overseas Travel Grants Pre-FEC
Starts:	18 August 2005	Ends:	17 September 2006	Value (£):	9,000
EPSRC Research Topic Classifications:	Materials Processing
EPSRC Industrial Sector Classifications:	Communications Electronics
Related Grants:
Panel History:
Summary on Grant Application Form
Summary.A new method of processing of transparent materials by ultrashort laser pulses attracts considerable interest in recent years. The approach is based on the fact that irradiation by a high-intensity beam from a femtosecond laser can permanently modify the structure of dielectric materials, thus changing their optical properties. The most common and significant result of such modification is the refractive index change, which finds a number of applications in manufacture of optoelectronic devices. In particular, optical waveguides, periodic structures and photonic crystal structures manufactured by this method have been demonstrated. The work so far has been mainly focused on amorphous materials and only several recent publications were dedicated to optical crystals. The physical mechanisms involved in modification of crystalline media remain, to large extent, unexplained. We propose to investigate one aspect of the above process / transition between purely nonlinear regime, observed at low repetition rate of the ultrafast laser, and the thermal regime, corresponding to the high repetition rates, when the nonlinear interaction of light with the medium is combined with the strong local heating of the material. Preliminary studies of thermal regime in amorphous media proved to be very fruitful and yielded several important results that helped to understand the physical mechanism of the inscription process in such media. Experimental evidence suggests that the same process in crystals occurs differently to that in glasses. Therefore, it is important to carry out a similar investigation in crystalline media. This collaboration project also aims to establish a link between the two groups that work in the area of femtosecond laser processing and possess complementary expertise. Prof. Mazur at Harvard is one of the pioneers of the femtosecond laser inscription. A number of important findings in this rapidly developing field have been produced by his group during the last decade. Research of the inscription regimes is one of the particularly strong lines of Prof. Mazur's research. In particular, a state of the art laser, dedicated to this work, has been designed and built in the group. On the other hand, Aston is one of only two universities in the U.K. active in the area of femtosecond laser inscription and working, among other topics, on the femtosecond processing of laser crystals. Several world's first results have been achieved at Aston in the last several years including, for example, inscription of buried waveguides in laser crystals. As a result, the work on the main topic of the project will be strengthened by contributions from both sides. We also anticipate that other topics of mutual interest will be identified during this collaborative work, thus benefiting both teams, research community and the relevant industry.
Key Findings
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Organisation Website:	http://www.aston.ac.uk