Title: Holographic ultrafast laser parallel micro/nano-processing 

Speaker: Prof. Geoff Dearden (University of Liverpool)   

Time: Nov. 16, 2015 09:00AM 

Venue: No. 320 Meeting Room, Building 3, IOS, CAS 

Abstract: Ultrafast lasers have been employed for high precision surface micro-structuring of materials such as metals, semi-conductors and dielectrics with little thermal damage. Due to the ultra short pulse duration, unwanted thermal effects can be avoided during the ultrafast laser-material interaction, hence achieving ‘cool processing’. To ensure this non-thermal effect, the laser fluence must be kept low, a few times the material’s ablation threshold. However, many commercial laser systems provide about 100 times higher energy density. Significant attenuation of the laser output is therefore required for many applications, which leads to a great deal of energy loss. With this limitation in mind, a holographic multi-beam ultrafast laser parallel processing technique, where the high energy density single output is split into many desired diffracted beams with arbitrary geometric arrangement, has been researched and demonstrated in the Laser Engineering Group, University of Liverpool. The multi-beam patterns are generated by phase modulation using computer generated holograms (CGHs) which are displayed on a Spatial Light Modulator (SLM). The ability to address these devices in real time and synchronize with scanning methods adds an additional flexibility to the processing. The results obtained demonstrate high precision micro/nano-fabrication of different kinds of materials with greatly increased process efficiency and throughput, indicating potential for many industrial applications.

Biography：Prof Geoff Dearden received his PhD from the University of Liverpool (Faculty of Engineering) in 1993. He developed a prototype (low-voltage) industrial free electron laser, the first working FEL to be successfully demonstrated in the UK. From 1995-2001, he managed several successful knowledge exchange and training projects in laser engineering with regional and pan-European SMEs and partner institutes, under EU funded ERDF, ESF and ADAPT schemes, during which time he co-founded the University’s Lairdside Laser Engineering Centre. He was appointed lecturer in the Faculty in 2001, senior lecturer in 2005, reader (associate professor) in 2009 and the chair of full professor in 2014. He is currently academic lead for laser engineering in the University (from 2012) and Research Lead for the School of Engineering (from 2014). His research has included laser ignition in IC engines, ultra short pulse laser processing, highly parallel laser processing using dynamic diffractive beam techniques, laser based direct write, laser bending/forming, FE modeling of laser applications and optical sensing of laser processes. He has collaborated on 35 projects, including contract and public funded research with more than 70 companies and knowledge exchange with over 200 SMEs. He has more than 200 scientific publications. He has supervised 25+ PhDs.