Single-shot extreme ultraviolet laser imaging of nanostructures with wavelength resolution

Abstract

We have demonstrated near-wavelength resolution microscopy in the extreme ultraviolet.Images of 50 nm diameter nanotubes were obtained with a single ~1 ns duration pulse from a desk-top size 46.9 nm laser. We measured the modulation transfer function of the microscope for three different numerical aperture zone plate objectives, demonstrating that 54 nm half-period structures can be resolved. The combination of near-wavelength spatial resolution and high temporal resolution opens myriad opportunities in imaging, such as the 2 ability to directly investigate dynamics of nanoscale structures. © 2007 Optical Society of America OCIS codes: 180.7460, 110.7440, 140.7240. Conventional visible light microscopy, the most convenient method to image small objects, is limited in resolution to about 200 nm [1]. A direct approach to overcome this limitation is the use of shorter wavelength extreme ultraviolet (EUV) or soft x-ray (SXR) light [2][3][4][5][6][7][8][9][10][11]. The highest spatial resolution achieved to date was obtained at the Advanced Light Source, a third generation synchrotron, where images with 15 nm half-period spatial resolution were acquired in exposure times of several seconds using 1.52 nm wavelength SXR light [2]. The need for compact and more broadly accessible full-field optical microscopes has motivated the development of microscopes based on high-harmonic light sources [5,6], plasma sources [7], and EUV/SXR lasers [8][9][10][11] . However, in all cases the spatial resolution achieved was several times the wavelength and/or required long exposures.In this letter we report what is to our knowledge the first EUV microscope that can obtain images with a spatial resolution approaching the wavelength of illumination, in this case λ = 46.9 nm (hν = 26.4 eV). Moreover, this microscope can obtain high spatial resolution images with a single laser shot, corresponding to ~1 ns temporal resolution, opening the possibility to investigate dynamics of nanoscale structures. This is possible due to the high brightness of the laser source, the high throughput of the optics, and the ability to tailor the spatial coherence of the laser to reduce coherence effects that can degrade single shot images. The entire microscope is extremely compact, occupying an area of 0.4 m × 2.5 m. The combination of these attributes 3 results in the demonstration of a high-resolution tool that can rapidly acquire full-field images for practical laboratory use in a broad range of applications.The microscope is schematically illustrated in Figure 1. Two spherical Sc/Si multilayer mirrors arranged in a Schwarzschild configuration with 13% throughput condense the light from the output of the laser onto the sample. A freestanding objective zone plate lens projects the image onto a charge-coupled device (CCD) detector with 13.5 µm pixels. The laser beam is created via a highly ionized plasma column that is generated by fast electrical discharge excitation of an argon-filled capillary [12]. It emits laser pulses with ~10 µJ of energy (2.4×...

Aspects of nanometer scale imaging with extreme ultraviolet (EUV) laboratory sources

“…In the compact EUV microscope utilizing a Fresnel optic, described in Section 5, the coherence of the source can be problematic due to coherence effects present in the microscope image, related to the properties of the laser beams [41]. Thus, for EUV imaging using the zone−plates, a compact laser plasma EUV source based on a double stream gas−puff target, presented in Fig.…”

Imaging and spectroscopy through plasmonic nano-probe

“…The diffraction limit of UV lights itself is down to 100 nm without a near-field probe. It has been reported that a compact capillary discharge UV laser can realize an imaging with a spatial resolution of 120-150 nm [86,87].…”

Nanoimaging using soft X-ray and EUV laser-plasma sources

“…Employing such radiation allows to visualize in a direct way through absorption contrast mechanism the flow of the gas, usually investigated with other techniques, such as the interferometry [10]. It was demonstrated that the radiation from a capillary discharge laser operating at a wavelength of = 46.9 nm EUV images permits to obtain a spatial resolution better than 55 nm [11,12], and that the spatial resolution of holographic images [13], employing the same EPJ Web of Conferences 167, 03001 (2018) https://doi.org/10.1051/epjconf/201816703001 PPLA 2017 wavelength, can be improved up to sub-50 nm [14]. A table top EUV laser emitting 13.2 nm wavelength radiation from Ni-like Cd ions was employed for imaging of with a sub-38 nm spatial resolution and a picosecond time resolution [15].…”