Harnessing attosecond technologies for functional nano and quantum materials

High harmonic quantum light sources provide an exquisite ability to harness and control short-wavelength light, enabling unprecedented control over the polarisation, spectral, temporal and orbital angular momentum waveforms. These represent the most complex coherent electromagnetic fields ever created, controlled on sub-Å spatial scales and sub-attosecond temporal scales, from the UV to the keV photon energy region.

These advances are providing powerful new tools for near-perfect X-ray imaging, for coherently manipulating quantum materials using light, and for designing more efficient nanoscale devices.

In this on-demand SelectScience^® webinar Dr. Margaret Murnane, Professor at the University of Colorado Boulder, explores capabilities and potential applications of tabletop high harmonic light sources.

Read on for the live Q&A session or register to watch the webinar at a time that suits you.

Q: Why should people choose to use high harmonic light sources compared to other conventional approaches?

MM: For microscopy, 10 nanometers spatial resolution can only be achieved with coherent light. Most of the X-ray and UV sources on the market are incoherent light sources that are not high brightness light bulbs. Using these sources you can certainly achieve sub-micron resolution but only of static samples. However, you will need high harmonic light sources if you want to achieve very high spatial resolution, be able to track heat transport and the mechanical properties.

Essentially, you could think about high harmonic light sources as the femtosecond lasers of the laser landscape. The femtosecond lasers are often used in eye surgeries or precise machining, so they're similar to high harmonic light source that no other electron or light-based technologies can achieve.

Q: What are the limits of X-ray energies you can generate through high harmonic generation?

MM: Right now, people have pushed it to a few kiloelectron volts but not in real applications. The real applications right now are mostly below 100 eV, which is matched to a lot of materials science and R&D questions. Going forward, I do see those applications being pushed out to at least 10 keV.

Q: What's the highest intensity possible with this light source?

MM: It depends on what you use to drive it. In our group, we tend to use 10-watt level femtosecond lasers because those are quite reasonable for graduate students and postdocs to maintain, and reasonable for an application.

Q: Can HHGD imaging help detect dopants?

MM: Yes, it does. We were able to detect the arsenic dopants underneath the nanostructures in the IMEC sample. We also can very sensitively detect if there's any contamination on the surface and interfacial roughness, etc. The UV light is very sensitive to the kinds of materials you shine it on. We've done the applications mostly in semiconductor and magnetic materials so far and we're now beginning to explore its applications in energy and other materials.

Q: Can this be used on graphene characterization?

MM: Yes, it can. It has been used to understand how the band structure of graphene and the electronic order changes, depending on what you put the graphene on.

Q: Do you think high harmonics could help advance the field of materials science?

MM: I think so. We’re collaborating with a bunch of material scientists right now. However, in many of these applications, we can't do everything, just like any laser technologies or any other technology, but we certainly have identified some nice areas to understand materials using the visible lasers whether it's nano-indentation or other types of approaches.

The one thing to remember is that our sample prep is very minimal. When we put one of these samples into liquid transport or image the sample, we just pop it in our microscope. We do not need to coat it or thin it, something that you might have to do for electromicroscopy or X-ray microscopy. This also allows us to make sure that the sample prep is not changing the sample. We've seen the situation of materials migration and we can avoid that.

Q: Where can I find your latest publications?

MM: Google Scholar keeps track of all my publications. We try to keep our website updated at JILA, you can Google and find our website to see a list of publications there. However, Google Scholar does a good job.

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