Dynamic wave-front generation for the characterization and testing of optical systems

Neil, Mark A. A.; Booth, M. J.; Wilson, Tony

doi:10.1364/ol.23.001849

Cited by 95 publications

(50 citation statements)

References 7 publications

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“…A femtosecond laser system producing pulses with sub-30 fs pulse duration at 800 nm wavelength and energies up to 1 mJ at a repetition rate of 1 kHz was used. Using a reflective-type SLM, a calculated phase profile is transferred from a computer to the SLM, and arbitrary phase patterns can be embedded in the fundamental laser beam 28 . These modified laser pulses are then focused (f = 300 mm, f /# = 15) into the interaction region to a diameter of roughly 40 µm, resulting in peak intensities of approximately 2 × 10 15 W cm −2 (ref.…”

Section: Methodsmentioning

confidence: 99%

Strong-field physics with singular light beams

et al. 2012

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Light beams carrying a point singularity with a screw-type phase distribution are associated with an optical vortex. The corresponding momentum flow leads to an orbital angular momentum of the photons 1-3 . The study of optical vortices has led to applications such as particle micro-manipulation 4,5 , imaging 6 , interferometry 7 , quantum information 8 and highresolution microscopy and lithography 9 . Recent analyses showed that transitions forbidden by selection rules seem to be allowed when using optical vortex beams 10 . To exploit these intriguing new applications, it is often necessary to shorten the wavelength by nonlinear frequency conversion. However, during the conversion the optical vortices tend to break up 11-13 . Here we show that optical vortices can be generated in the extreme ultraviolet (XUV) region using high-harmonic generation 14,15 . The singularity impressed on the fundamental beam survives the highly nonlinear process. Vortices in the XUV region have the same phase distribution as the driving field, which is in contradiction to previous findings 16 , where multiplication of the momentum by the harmonic order is expected. This approach opens the way for several applications based on vortex beams in the XUV region.Places where physical quantities become infinite or change abruptly are called singularities. The presence of phase dislocations (singularities) in the wavefront of a light beam determines both the phase and intensity structure around them. As the phase becomes indeterminate at singularities, both the real and the imaginary parts of the field amplitude (that is, also the field intensity) vanish. The characteristic helical phase profiles of optical vortices are described by exp(imθ) multipliers, where θ is the azimuthal coordinate and the integer number m is their topological charge, also called dislocation strength or winding number.Recalling the fact that in free space the Poynting vector gives the momentum flow, for helical phase fronts the Poynting vector has an azimuthal component that produces an orbital angular momentum parallel to the axis of the beam. The momentum circulates around the beam axis, so such beams are said to contain an optical vortex. As has been shown 1-3 , an m-fold charged optical vortex beam carries an orbital angular momentum of mh per photon independent of the spin angular momentum (that is, the polarization state). It was shown that transitions that are forbidden by known selection rules in the electric and magnetic dipole approximation seem to be allowed when using optical vortex beams 10 . This provides a new degree of freedom in the spectroscopy of forbidden transitions. Multi-coloured optical vortices can be generated through a nonlinear frequency-conversion process such as second-harmonic generation 16 or four-wave mixing, which is an important process in the white-light vortex generation. However, as predicted in ref. 11 and observed in ref. 12, vortex breakup in self-focusing nonlinear media is an important issue for supercontinuum vortex genera...

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Section: Methodsmentioning

confidence: 99%

Strong-field physics with singular light beams

et al. 2012

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“…Tilts larger than 45 waves were avoided, as above this value the corresponding binarized grating thickness was observed to decrease to below the minimum required for Nyquist sampling, and using equal values for X and Y tilt allowed for maximal separation of orders in the Fourier plane. The desired phase profile, ϕ D , is transformed into a binary representation, which is displayed on the SLM according to [4] ϕ B x; y π if cos ϕx; y ≥ 0 0 otherwise ;…”

Section: Theory and Simulationmentioning

confidence: 99%

“…The Fourier transform of square waves can be represented as an infinite sum of odd exponential functions [4,7]:…”

Section: Theory and Simulationmentioning

confidence: 99%

“…Ferroelectric-liquid-crystal-on-silicon (FLCOS) spatial light modulators (SLMs) allow for the implementation of rapidly reconfigurable holograms into an interferometric system [4], which enables the optical wavefront in one arm of the interferometer to be arbitrarily distorted on demand to compensate for a variety of optical surfaces. These devices can also add new flexibility to the incorporation of wellknown phase shifting techniques [5], as the phase steps can be programmed directly into the holographic display, and thus eliminate the need for separate phase-shifting elements.…”

Section: Introductionmentioning

confidence: 99%

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Traceable interferometry using binary reconfigurable holograms

2014

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The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. We describe the characterization of a ferroelectric-liquid-crystal-on-silicon (FLCOS) spatial light modulator (SLM) in the production of holograms for use in interferometric metrology. It has already been shown that such a device can be used in producing small-amplitude arbitrary reference surfaces with small but appreciable errors due to the contaminating effect of higher-order structures being propagated through the spatial filter. Here we further quantify the size of these residuals for increasingly large aberrations up to nine waves rms Zernike astigmatism, showing a Zernike-corrected rms wavefront error of roughly 0.06 waves with high vibrational stability. We also present measurements of a vacuum window element using the FLCOS device to drastically reduce interferometric fringe density, showing a residual wavefront error of 0.046 waves rms with dominant components originating from test piece structure rather than holographic errors.

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“…dark region,---1 and bright region= +1). (right column) of Zi=5,6,7,8,9,10,14,and 15 (from top to bottom). ORMS is taken as 0.447 as it corresponds to Strehl ratio=0.8, the minimum figure considered for a well corrected optical system.…”

Section: Introductionmentioning

confidence: 99%

Programmable diffractive optics for laser scanning confocal microscopy

Boruah

Neil

2007

SPIE Proceedings

Self Cite

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Coherent light beams find applications in several exciting research areas where it is important to have absolute control over the phase and amplitude properties of the light beams.To name a few, in applications such as microscopy, optical trapping, interferometry etc. it is imperative to have dynamic control over the properties of the beam. One way of achieving this is with the help of a computer controlled diffractive optical element such as a liquid crystal spatial light modulator (LCSLM). Based on the principle of holography, such a technique can provide dynamic control over amplitude, phase and polarisation state across a coherent beam.This work describes about a ferro-electric liquid crystal spatial light modulator (FLC-SLM) system acting as a programmable diffractive optical element. The efficiency of the system to detect and correct aberrations in laser beams were demonstrated. The ultra sensitivity of singular light beams to the presence of azimuthal aberrations were observed and a novel aberration sensor based on these findings were implemented. The synchronisation of the display holograms on the FLCSLM panel with the acquisition of a CCD camera is demonstrated in a programmable reference beam phase stepping interferometry experiment.Laser scanning confocal microscopy is a widely used technique for the electronic visualization of optically sectioned microscopic structures. The information available from such a system is limited by the intensity and polarisation properties of the point spread function (PSF) at the sample plane, which are in turn dependent on the optical system and the sample being imaged. Aberrations due to incorrect optics or the sample itself may significantly degrade the PSF there by reducing the resolution and the signal available for image formation. Also the information obtained from a laser scanning confocal system working in the epi-fluorescence mode will also depend on the polarisation properties of the PSF, as molecular absorption and emission cross-sections are polarisation dependant. These polarisation properties can be particularly important for high resolution microscopy such as STED and molecular alignment studies when high numerical aperture lenses are used that can result in complex polarisation structure within the PSF. The thesis develops the theory necessary to understand the vectorial behaviour of the 3D PSF for an arbitrarily polarised beam. The design and implementation of a beam scanning optical microscope system, that uses an FLCSLM to control the optical field in the illumination pupil of the microscope objective, are described. The performance of the system in engineering and reconfiguring the 3D PSF is demonstrated. Use of programmable diffractive optics to generate different depletion beams for STED microscopy is also demonstrated. 2To My Parents 3

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Dynamic wave-front generation for the characterization and testing of optical systems

Cited by 95 publications

References 7 publications

Strong-field physics with singular light beams

Strong-field physics with singular light beams

Traceable interferometry using binary reconfigurable holograms

Programmable diffractive optics for laser scanning confocal microscopy

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