Kapteyn Murnane Laboratories

We present the discovery of seven molecular clouds in the radio galaxy B2 0902+34 at redshift z=3.4. These clouds are detected as CO(0-1) absorption features against the bright radio continuum, and spectrally resolved using the Karl G. Jansky Very Large Array (VLA). The velocity dispersion of the individual absorption components ranges from 3-7 km/s, which is similar to values observed for molecular clouds in the Milky Way and nearby galaxies, and imply cloud radii of R~10$^{1-2}$ pc. The absorbing clouds are found in a region of high obscuration inside a 30 kpc wide stellar nebula, as revealed by rest-frame near-ultraviolet imaging performed with the Hubble Space Telescope (HST). The fact that we spectrally resolve molecular clouds at the onset of Cosmic Noon opens prospects for studying cloud chemistry and physics that drive the formation of stars in the Early Universe.

The industry is developing extreme-ultraviolet wavelength (EUV) techniques to measure critical dimensions (CDs) in logic fabrication. As nascent approaches are unveiled, evaluations against reference metrologies are essential to motivate development at higher speeds using industrially relevant length scales. The parametric geometries determined from EUV diffractometry data using a tabletop coherent high-harmonic generation (HHG) source are compared against dimensions from synchrotron-based CD small angle x-ray scattering (CD-SAXS) for four line-space arrays with CDs below 50nm. An EUV imaging reflectometer captures the 0th order reflection and the 1st order diffraction intensities as functions of grazing angle. The 1st order intensities are functions of five wavelengths from the spectral comb of this HHG source. Fits to these data using rigorous couple-wave analysis (RCWA) electromagnetic simulations yield parametric values and uncertainties. EUV diffractometry simulations match well in general with the measured data after accounting for cross-sectional geometry and experimental conditions. EUV diffractometry line widths correlate well against those of CD-SAXS at the mid-height of the latter. These promising results were obtained using a general-purpose prototype coherent EUV reflectometer. Routes for further enhancing the sensitivity and accuracy are presented and are in progress.

We present a unique instrument, designed to characterize the composition, geometry, topography, and interface quality of 2D heterostructures. We demonstrate three modes of characterizations, including reflectometry, scatterometry, and coherent diffractive imaging reflectometry.

Ptychographic coherent diffractive imaging enables diffraction-limited imaging of nanoscale structures at extreme ultraviolet and x-ray wavelengths, where high-quality image-forming optics are not available. However, its reliance on a set of diverse diffraction patterns makes it challenging to use ptychography to image highly periodic samples, limiting its application to defect inspection for electronic and photonic devices. Here, we use a vortex high harmonic light beam driven by a laser carrying orbital angular momentum to implement extreme ultraviolet ptychographic imaging of highly periodic samples with high fidelity and reliability. We also demonstrate, for the first time to our knowledge, ptychographic imaging of an isolated, near-diffraction-limited defect in an otherwise periodic sample using vortex high harmonic beams. This enhanced metrology technique can enable high-fidelity imaging and inspection of highly periodic structures for next-generation nano, energy, photonic, and quantum devices.

The origin of the pseudogap in many strongly correlated materials has been a longstanding puzzle. Here, we present experimental evidence that many-body interactions among small Holstein polarons, i.e., the formation of bipolarons, are primarily responsible for the pseudogap in (TaSe4)2I. After weak photoexcitation of the material, we observe the appearance of both dispersive (single-particle bare band) and flat bands (single-polaron sub-bands) in the gap by using time- and angle-resolved photoemission spectroscopy. Based on Monte Carlo simulations of the Holstein model, we propose that the melting of pseudogap and emergence of new bands originate from a bipolaron to single-polaron crossover. We also observe dramatically different relaxation times for the excited in-gap states in (TaSe4)2I (∼600 fs) compared with another 1D material Rb0.3MoO3 (∼60 fs), which provides a new method for distinguishing between pseudogaps induced by polaronic or Luttinger-liquid many-body interactions.

Spatiotemporal orbital angular momentum (ST-OAM) of light is an emergent, spatiotemporally sculptured light. Such spatiotemporal optical vortices carry transverse OAM and exhibit novel properties. However, the lack of a simple and straightforward characterization method substantially slows its progress and potential adaptions for future applications. Here we demonstrated a simple, stationary, single-frame method to quantitatively characterize ST-OAM pulses. Our new method can measure the presence of ST-OAM, space-time topological charge numbers, OAM helicity, pulse dispersion, and beam divergence. We also investigated the nonlinear properties of ST-OAM pulses, uncovering the conservation of space-time topological charges in a second-harmonic generation process.

Coherent short wavelength sources enable high resolution probes of magnetic skyrmions. 3D vector ptycho tomography enables high resolution 3D static imaging of nanoscale spin textures, while ultrafast coherent EUV light enables dynamic magnetic scattering measurements.

We report a compact, cryogenic Yb:YAG regenerative amplifier that delivers >19-mJ energy pulses at 1-kHz with near-TEM00 spatial profile. The excellent power and pointing stabilities are ideal for OPCPA pumping over weeks-long continuous operation.

The papers in this special section focus on ultrafast science and technology. This field has seen a big highlight, since the Nobel prize in physics for 2018 was announced in high intensity lasers. The application space integrates state-of-the-art photonics techniques coming from the areas of quantum electronics, lasers, fiber optics and electro-optics to chemistry. This field continues to vastly expand with advanced developments across the entire spectrum of ultrafast applications ranging from fundamental laboratory studies to high harmonic generation, attosecond science, non-linear optics, and laser innovation. Recently developed innovative technologies have made a significant impact on ultrafast research in many areas, and is now expanding out of the realm of fundamental science research to industrial applications. This section examines some of the latest leading-edge developments in generating, propagating, measuring, and applications of ultrafast pulses of light.

EUV lithography is promising for addressing upcoming, <10nm nodes for the semiconductor industry, but with this promise comes the need for reliable metrology techniques. In particular, there is a need for actinic mask inspection in which the imaging wavelength matches that of the intended lithography process, so that the most relevant defects are detected. Here, we demonstrate tabletop, ptychographic, coherent diffraction imaging (CDI) in reflection- and transmission-modes of extended samples, using a 13 nm high harmonic generation (HHG) source. We achieve the first sub-wavelength resolution EUV image (0.9λ) in transmission, the highest spatial resolution using any 13.5 nm source to date. We also present the first reflection-mode image obtained on a tabletop using 12.7 nm light. This work represents the first 12.7 nm reflection-mode image using any source of a general sample.