Transient optical gratings for short pulse, short wavelength ionising radiation studies - Opportunities and approaches

Loss of short wavelength phase information occurs when event sizes exceed radiation wavelengths, making conventional holography impossible above a material-dependent quantum energy limit. Despite this, and prior to the invention of holography or lasers, Bragg's X-ray microscope [1] opened the door to optical computation in short-wavelength studies using spatially coherent visible light, including phase retrieval methods. This optical approach lost ground to semiconductor detection and digital computing in the 1960s. Since then, visible optics including spatial light modulators, array detectors and femtosecond lasers have become widely available, routinely allowing versatile and computer-interfaced imposition of optical phase, molecular coherent control, and detection. Today, free electron lasers (FELs) begin to offer opportunities for atomic resolution and ultrafast pump-probe studies. Thus we investigate an overlooked aspect of Bragg's X-ray microscope: the incoherent ionising radiation to coherent visible (IICV) spatial light modulator (SLM) conversion that is a necessary prerequisite for coherent optical computations. Some potential opportunities and approaches are outlined.