Abstract :

High harmonic generation (HHG) provides a lab-scale source of ultrafast, spatially coherent X-rays previously only available at synchrotrons or free electron lasers. It can produce femtosecond pulses of radiation in the spectral region from ~40nm down to 1 nm by nonlinear optical frequency conversion from the near IR. The nonlinear optical nature of the HHG process means that the generated radiation retains the spatial coherence properties of the original source, which ideal for applications in lensless or diffractive imaging. Lensless imaging relies on numerical algorithms to replace the action of lenses in an imaging experiment. As lenses are hard to make in the soft X-ray regime, the diffraction pattern from an object is collected using a camera. All phase information is lost in the collection process, but this phase information can be regenerated mathematically in some circumstances, allowing the formation of an image. The spatial coherence of an HHG source makes it well-suited to this technique of Coherent Diffractive imaging. This talk will explain the principles of HHG, and show how HHG radiation can be used in a new generation of lensless coherent imaging applications in the soft X-ray spectral region.

ABOUT THE SPEAKER:

Dr. Bill Brocklesby is a Reader at the Optoelectronics Research Centre at Southampton, and an associate member of the School of Physics and Astronomy. His research interests, originating from his doctoral work in Oxford and postdoctoral work at AT&T Bell Laboratories, span spectroscopy and microscopy of a wide range of materials and devices. For the last 10 years he has worked in the area of nanoscale imaging, with particular emphasis on the study of optical waveguide devices, demonstrating subwavelength optical imaging within devices such as fibre Bragg gratings and microstructured fibres, and nonlinear waveguides. He has been a member of the steering committee of the EPSRC-funded Nano-optics Network, and is a regular contributor to near field optics conferences, such as NFO. He has extensive experience with other microscope and scanning probe techniques such as micro-Raman spectroscopy, AFM, and STM, and ultrafast laser technology. He has over 50 journal papers in these research areas.