Tabletop coherent diffractive microscopy with extreme ultraviolet light from high harmonic generation Daisy A. Raymondson* a , Richard L. Sandberg a , William F. Schlotter b , Kevin S. Raines c , Chan La-o- Vorakiat a , Ethan Townsend a , Anne Sakdinawat d , Ariel Paul a , Jianwei Miao c , Margaret M. Murnane a , and Henry C. Kapteyn a a Department of Physics and JILA, University of Colorado and NIST, 440 UCB, Boulder, CO, USA 80309; b Institute for Experimental Physics, University of Hamburg, Luruper Chausee 149,22761 Hamburg, Germany; c Department of Physics and Astronomy and California NanoSystems Institute, University of California, Los Angeles, California, USA; Center for X-ray Optics, Lawrence Berkeley National Lab, University of California at Berkeley, Berkeley, California ABSTRACT 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. Keywords: Coherent diffractive imaging, x-ray microscopy, ultrafast optics, high harmonic generation 1. INTRODUCTION X-ray and extreme ultraviolet imaging offers several advantages over optical imaging, including higher resolution proportional to wavelength and the ability to access numerous chemical absorption edges in the soft x-ray and extreme ultraviolet (EUV) region of the spectrum. Soft x-ray microscopy on a synchrotron source has shown resolution down to 15 nm 1 . Two limitations to imaging in the EUV are the limited availability of high-brightness sources for applications, and the limited options for imaging optics. Since materials are highly absorbing in this region of the spectrum, no refractive lenses are available. Available optics include diffractive zone plate lenses and reflective multilayer mirror optics. Both are very lossy, 10% to 70% throughput per optical element, and both are prone to aberrations. Compact sources for EUV imaging are crucial to expanding access for applications such as biological microscopy and lithographic mask inspection. For compact sources such as high harmonic generation (HHG), coherent diffractive imaging without the use of imaging optics provides an attractive means of making use of the available flux. 1.1 Coherent diffractive “lensless” imaging Coherent diffractive imaging of nonperiodic samples was first proposed by David Sayre in 1952 2 as an extension of x- ray crystallography. By sampling the Bragg peaks from a sample at higher than the Nyquist frequency for the desired spatial resolution, a condition known as oversampling, it is possible to capture the information necessary to uniquely *daisy.raymondson@colorado.edu; phone 1 303 492-7764; fax 1 303 492-5235; http://jilawww.colorado.edu/kmgroup/ Best Student Paper Award Metrology, Inspection, and Process Control for Microlithography XXIII, edited by John A. Allgair, Christopher J. Raymond Proc. of SPIE Vol. 7272, 72720F · © 2009 SPIE · CCC code: 0277-786X/09/$18 · doi: 10.1117/12.814313 Proc. of SPIE Vol. 7272 72720F-1