Daisy Raymondson

Ultrahigh 22 nm resolution coherent diffractive imaging using a desktop 13 nm high harmonic source.

New diffractive imaging techniques using coherent x-ray beams have made possible nanometer-scale resolution imaging by replacing the optics in a microscope with an iterative phase retrieval algorithm. However, to date very high resolution imaging (< 40 nm) was limited to large-scale synchrotron facilities. Here, we present a significant advance in image resolution and capabilities for desktop soft x-ray microscopes that will enable widespread applications in nanoscience and nanotechnology. Using 13 nm high harmonic beams, we demonstrate a record 22 nm spatial resolution for any tabletop x-ray microscope. Finally, we show that unique information about the sample can be obtained by extracting 3-D information at very high numerical apertures.

High numerical aperture tabletop soft x-ray diffraction microscopy with 70-nm resolution.

Light microscopy has greatly advanced our understanding of nature. The achievable resolution, however, is limited by optical wavelengths to ≈200 nm. By using imaging and labeling technologies, resolutions beyond the diffraction limit can be achieved for specialized specimens with techniques such as near-field scanning optical microscopy, stimulated emission depletion microscopy, and photoactivated localization microscopy. Here, we report a versatile soft x-ray diffraction microscope with 70- to 90-nm resolution by using two different tabletop coherent soft x-ray sources—a soft x-ray laser and a high-harmonic source. We also use field curvature correction that allows high numerical aperture imaging and near-diffraction-limited resolution of 1.5λ. A tabletop soft x-ray diffraction microscope should find broad applications in biology, nanoscience, and materials science because of its simple optical design, high resolution, large depth of field, 3D imaging capability, scalability to shorter wavelengths, and ultrafast temporal resolution.

Tabletop soft-x-ray Fourier transform holography with 50 nm resolution

We present what we believe to be the first implementation of Fourier transform (FT) holography using a tabletop coherent x-ray source. By applying curvature correction to compensate for the large angles inherent in high-NA coherent imaging, we achieve image resolution of 89 nm using high-harmonic beams at a wavelength of 29 nm. Moreover, by combining holography with iterative phase retrieval, we improve the image resolution to <53 nm. We also demonstrate that FT holography can be used effectively with short exposure times of 30 s. This technique will enable biological and materials microscopy with simultaneously high spatial and temporal resolution on a tabletop soft-x-ray source.

Tabletop Lensless Imaging Using Coherent High Harmonic Beams

We present the first demonstration of lensless imaging using coherent high harmonic beams. This coherent imaging technique avoids traditional diffractive optics, and is transparently extendable to shorter wavelengths without aberrations.

Near diffraction limited coherent diffractive imaging with tabletop soft x-ray sources

Tabletop coherent x-ray sources hold great promise for practical nanoscale imaging, in particular when coupled with diffractive imaging techniques. In initial work, we demonstrated lensless diffraction imaging using a tabletop high harmonic generation (HHG) source at 29 nm, achieving resolutions ~ 200 nm. In recent work, we significantly enhanced our diffractive imaging resolution by implementing a new high numerical aperture (up to NA=0.6) scheme and field curvature correction where we achieved sub-100 nm resolution. Here we report the first demonstration of Fourier transform holography (FTH) with a tabletop SXR source, to acquire images with a resolution ≈ 90 nm. The resolution can be refined by applying phase retrieval. Additionally, we show initial results from FTH with 13.5 nm HHG radiation and demonstrate ~ 180 nm resolution.

Coherent imaging of laser-plasma interactions using high-harmonic EUV Light

We demonstrate that light generated using high-harmonic conversion in waveguides has very high spatial coherence at 30 nm and 13nm. Using this light source, we demonstrate EUV images of the explosion of a micron-size water droplet illuminated by an intense femtosecond laser using an all-reflective, double-multilayer mirror setup and a CCD camera as an image recording device.

Ultrafast optical parametric oscillator pumped by an all normal dispersion (ANDi) Yb:Fiber oscillator

We describe a 13 nJ, 100 fs, 60 MHz Yb:Fiber ANDi oscillator that pumps a MgO2:PPLN optical parametric oscillator (OPO), producing up to 300 mW (signal+idler) of total output, and overall efficiency of 37%.

Tabletop coherent diffractive microscopy with soft x-rays from high harmonic generation at 13.5 nm

We demonstrate lensless diffractive microscopy with 92nm resolution using 13.5nm light from high harmonic generation. Fast image retrieval with Fourier transform holography is shown, and we present paths to refining the images to higher resolution.

Lensless Microscopy and Holography with 60 nm Resolution using Tabletop Coherent Soft X-Rays

We demonstrate high numerical aperture lensless diffractive imaging and Fourier transform holography using high harmonic generation from an ultrafast laser system. The HHG source operates at 29 nm or 13 nm wavelength and achieves 60 nm resolution.

Tabletop coherent diffractive microscopy with extreme ultraviolet light from high harmonic generation

We demonstrate lensless diffractive microscopy using a tabletop source of extreme ultraviolet (EUV) light from high harmonic generation at 29 nm and 13.5 nm. High harmonic generation has been shown to produce fully spatially coherent EUV light when the conversion process is well phase-matched in a hollow-core waveguide. We use this spatial coherence for two related diffractive imaging techniques which circumvent the need for lossy imaging optics in the EUV region of the spectrum. Holography with a reference beam gives sub-100 nm resolution in short exposure times with fast image retrieval. Application of the Guided Hybrid Input-Output phase retrieval algorithm refines the image resolution to 53 nm with 29 nm light. Initial images using the technologically important 13.5 nm wavelength give 92-nm resolution in a 10-minute exposure. Straightforward extensions of this work should also allow near-wavelength resolution with the 13.5 nm source. Diffractive imaging techniques provide eased alignment and focusing requirements as compared with zone plate or multilayer mirror imaging systems. The short-pulsed nature of the extreme ultraviolet source will allow pump-probe imaging of materials dynamics with time resolutions down to the pulse duration of the EUV.