Peter Baksh
University of Southampton
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Featured researches published by Peter Baksh.
Optics Express | 2016
Michal Odstrčil; Peter Baksh; Stuart A. Boden; Rachel Card; John E. Chad; Jeremy G. Frey; W.S. Brocklesby
Ptychography is a scanning coherent diffractive imaging (CDI) technique that relies upon a high level of stability of the illumination during the course of an experiment. This is particularly an issue for coherent short wavelength sources, where the beam intensity is usually tightly focused on the sample in order to maximize the photon flux density on the illuminated region of the sample and thus a small change in the beam position results in a significant change in illumination of the sample. We present an improved ptychographic method that allows for limited stability of the illumination wavefront and thus significantly improve the reconstruction quality without additional prior knowledge. We have tested our reconstruction method in a proof of concept experiment, where the beam instability of a visible light source was emulated using a piezo driven mirror, and also in a short wavelength microscopy CDI setup using a high harmonic generation source in the extreme ultraviolet range. Our work shows a natural extension of the ptychography method that paves the way to use ptychographic imaging with any limited pointing stability coherent source such as free electron or soft X-ray lasers and improve reconstruction quality of long duration synchrotron experiments.
Journal of Optics | 2013
Aaron Parsons; Richard T. Chapman; Peter Baksh; B. Mills; S. Bajt; W.S. Brocklesby; Jeremy G. Frey
Conventional coherent diffractive imaging (CDI) techniques rely on inversion of the two-dimensional phase problem in the fully coherent limit. Current work using synchrotrons has shown that by introducing a flexible parameter in a technique known as polyCDI, some reduced temporal coherence with relative bandwidth ~3% can be tolerated for simple non-dispersive objects. We demonstrate that using a high harmonic source with modulated spectral characteristics, although the excellent temporal coherence properties are lost in detection, it is possible to increase the tolerable relative bandwidth to ~20% by using the shrinkwrap technique and treating the data as if they were fully coherent but noisy. This reduces the integration time by a factor of ~5. This result is critical for the future use of lab-based sources of extreme ultraviolet and soft x-rays for CDI of non-dispersive objects, and we anticipate that it will improve results at synchrotron sources also.
Optics Letters | 2016
Peter Baksh; Michal Odstrčil; Hyun-su Kim; Stuart A. Boden; Jeremy G. Frey; W.S. Brocklesby
High-harmonic generation (HHG) provides a laboratory-scale source of coherent radiation ideally suited to lensless coherent diffractive imaging (CDI) in the EUV and x-ray spectral region. Here we demonstrate transmission extreme ultraviolet (EUV) ptychography, a scanning variant of CDI, using radiation at a wavelength around 29 nm from an HHG source. Image resolution is diffraction-limited at 54 nm and fields of view up to ∼100 μm are demonstrated. These results demonstrate the potential for wide-field, high-resolution, laboratory-scale EUV imaging using HHG-based sources with potential application in biological imaging or EUV lithography pellicle inspection.
Optics Express | 2016
Michal Odstrčil; Peter Baksh; C.B.E. Gawith; Ranko M. Vrcelj; Jeremy G. Frey; W.S. Brocklesby
Ptychographic Coherent diffractive imaging (PCDI) is a significant advance in imaging allowing the measurement of the full electric field at a sample without use of any imaging optics. So far it has been confined solely to imaging of linear optical responses. In this paper we show that because of the coherence-preserving nature of nonlinear optical interactions, PCDI can be generalised to nonlinear optical imaging. We demonstrate second harmonic generation PCDI, directly revealing phase information about the nonlinear coefficients, and showing the general applicability of PCDI to nonlinear interactions.
Applied Physics Express | 2016
Hyun-su Kim; Peter Baksh; Michal Odstrčil; Magdalena Miszczak; Jeremy G. Frey; Larissa Juschkin; W.S. Brocklesby
We demonstrate interference lithography using a high-harmonic source. Extreme ultraviolet (EUV) radiation is produced by high-harmonic generation with 800 nm light from a femtosecond Ti:sapphire laser (40 fs pulses, 1 kHz, 2 W average power) in argon gas. Interference patterns created using Lloyds mirror setup and monochromatized radiation at the 27th harmonic (29 nm) are recorded using a ZEP-520A photoresist, producing features with <200 nm pitch. The effect of the use of femtosecond pulsed EUV radiation on the recorded pattern is investigated. The capability of the high-harmonic source for high-resolution patterning is discussed.
Proceedings of SPIE | 2015
Michal Odstrčil; Peter Baksh; Hyun-su Kim; Stuart A. Boden; W.S. Brocklesby; Jeremy G. Frey
With the aim of improving imaging using table-top extreme ultraviolet sources, we demonstrate coherent diffraction imaging (CDI) with relative bandwidth of 20%. The coherence properties of the illumination probe are identified using the same imaging setup. The presented methods allows for the use of fewer monochromating optics, obtaining higher flux at the sample and thus reach higher resolution or shorter exposure time. This is important in the case of ptychography when a large number of diffraction patterns need to be collected. Our microscopy setup was tested on a reconstruction of an extended sample to show the quality of the reconstruction. We show that high harmonic generation based EUV tabletop microscope can provide reconstruction of samples with a large field of view and high resolution without additional prior knowledge about the sample or illumination.
Journal of Physics: Conference Series | 2017
Peter Baksh; Michal Odstrčil; Aaron Parsons; Jo Bailey; Katrin Deinhardt; John E. Chad; W.S. Brocklesby; Jeremy G. Frey
Coherent diffractive imaging (CDI) has become a standard method on a variety of synchrotron beam lines. The high brilliance short wavelength radiation from these sources can be used to reconstruct attenuation and relative phase of a sample with nanometre resolution via CDI methods. However, the interaction between the sample and high energy ionising radiation can cause degradation to sample structure. We demonstrate, using a laboratory based high harmonic generation (HHG) based extreme ultraviolet (EUV) source, imaging a sample of hippocampal neurons using the ptychography method. The significant increase in contrast of the sample in the EUV light allows identification of damage induced from exposure to 7.3 keV photons, without causing any damage to the sample itself.
Proceedings of SPIE | 2016
Alain Jody Corso; Stefano Bonora; Paola Zuppella; Peter Baksh; Magdalena Miszczak; W.S. Brocklesby; Zhanshan Wang; P. Nicolosi; Maria Guglielmina Pelizzo
The growing interest in the study of the extreme ultraviolet (EUV) radiation-matter interaction is feeding up the development of new technologies able to overcame some current technological limits. Adaptive optics is an established technology already widely used for wavefront correction in many applications such as astronomical telescopes, laser communications, high power laser systems, microscopy and high resolution imaging systems. Although this technology is already exploited in the EUV and X-ray range, its usage is only feasible in systems with a grazing incidence configuration. On the other hand, the development of a EUV normal incidence adaptive optics can open new interesting possibilities in many different fields ranging from free electron laser and synchrotron applications up to EUV photolithography. In this work we report the preliminary results achieved in the developing of a normal incidence EUV multilayered adaptive mirror tuned at 30.4nm. The proper functioning and potential applications of such device have been demonstrated by using a High order Harmonics Generation (HHG) source.
Optics Letters | 2016
Peter Baksh; Michal Odstrčil; Hyun-su Kim; Stuart A. Boden; Jeremy G. Frey; W.S. Brocklesby
This note amends the list of funders in a recent Letter [Opt. Lett.41, 1317 (2016)OPLEDP0146-959210.1364/OL.41.001317].
Archive | 2016
Hyun-su Kim; Peter Baksh; Michal Odstrčil; Magdalena Miszczak; Jeremy G. Frey; Larissa Juschkin; W.S. Brocklesby
We demonstrate interference lithography using a high-harmonic source. Extreme ultraviolet (EUV) radiation is produced using high harmonic generation with 800 nm light from a femtosecond Ti:Sapphire laser (40 fs pulses, 1 kHz, 2W average power) in argon gas. Interference patterns created using a Lloyd’s mirror setup and monochromatized radiation at the 27th harmonic (29 nm) are recorded using ZEP-520A photoresist, producing features with