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.