Research Overview

Henry Kapteyn and Margaret Murnane photo.

Our group is developing new probes of quantum matter using coherent X-ray beams, which have undergone a revolution in the past decade. More than 50 years after the demonstration of the visible laser, it is finally possible to generate laser-like beams spanning the deep-UV, extreme ultraviolet (EUV) and soft X-ray regions of the spectrum by harnessing high harmonic upconversion of femtosecond lasers. Moreover, by combining phase matching techniques and selection rules, we can achieve exquisite “quantum” control over x-ray light. It is now possible to produce short wavelength waveforms with controlled spectral and temporal shapes, polarization state, and phase structure. Exciting recent advances also include the first sub-wavelength imaging at short wavelengths, the ability to directly manipulate spins in materials using light, the first methods to measure the full mechanical properties of ultrathin films and nanostructured media, uncovering new regimes of nanoscale heat flow, as well as routes for mapping new states and phases in quantum materials. Ultrafast coherent EUV and x-ray beams are thus becoming indispensable tools in the race to develop new nanoscale and quantum devices.

We welcome trainees from physics, materials science, engineering and chemistry to work together to solve grand-challenge scientific problems that are also at the technological forefront. Trainees from our group go on to positions in academe, industry and national laboratories.

Research Areas

  • Ever since the invention of the visible laser over 50 years ago, scientists have been striving to create lasers that generate coherent beams at shorter wavelengths i.e. the extreme UV (EUV) and soft X-ray (SXR) regions of the spectrum. This quest has led to the construction of large facilities, such as kilometer-scale x-ray free-electron lasers, to reach the keV photon energy region.

  • Magnetism has been the subject of scientific inquiry for more than 2000 years. However, it is still an incompletely understood phenomenon. The fundamental length and time scales for magnetic phenomena range from Å (exchange lengths) and sub-femtoseconds (exchange splitting) on up. 

  • High harmonics are ideal as the illumination source for time- and angle-resolved photoemission spectroscopy (trARPES), which can measure the full electronic band structure of a material. Moreover, a new generation of ultrafast (~50-100fs), MHz rep rate, VUV (1-20eV) highly-cascaded high harmonics driven by compact fiber lasers have 10-100meV energy resolution, and are ideal for spin-resolved ARPES (Optica 7, 832 (2020).

  • Although x-ray imaging has been explored for decades, and visible-wavelength microscopy for centuries, it is only recently that the spectral region in between―the extreme ultraviolet (EUV)―has been explored for imaging nanostructures and nanomaterials.

  • Heat transport is driven by a thermal gradient, flowing from hot to cold regions in a material. However, at dimensions <100nm, bulk models no longer accurately predict the transport properties of materials. Because no complete models of nanoscale heat transport were available, it was assumed instead that bulk-like diffusive heat transport was valid—provided that an effective parameter, such as a size-dependent thermal conductivity, was incorporated.

  • Nanoparticles exhibit a surface-area-to-volume ratio many orders of magnitude higher than bulk materials, allowing them to serve as powerful catalysts for chemical reactions, both in the laboratory and as atmospheric aerosols.

  • The demand for faster, more efficient, and more compact nanoelectronic devices, like smartphone chips, requires engineers to develop increasingly complex designs. To achieve this, engineers use layer upon layer of very thin films – as thin as only a couple strands of DNA – with impurities added, to tailor the function. 

  • Science and technology are inextricably linked and continue to drive each other. Ultrafast lasers have revolutionized our understanding of how molecules and materials work and how charges, spins, phonons and photons interact dynamically. In past research, our group designed Ti:sapphire lasers that operate at the limits of pulse duration and stability, with adjustable pulse durations from 7 fs on up.