How to make femtosecond pulses overlap

Maznev, A. A.; Crimmins, Timothy F.; Nelson, Keith A.

doi:10.1364/ol.23.001378

Cited by 182 publications

(95 citation statements)

References 8 publications

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“…The coherence and zero-time delay are maintained across the entire cross-section of the tilted pulses despite their different propagation directions, and the interference occurs in the entire spot area due to DOE ability to tilt short pulses [22,23]. The wavefront of the beams is not tilted after passing the beamsplitter.…”

Section: Experimental Set-ups Of Holographic Lithography and Their Fementioning

confidence: 99%

Fabrication of periodic micro-structures by holographic lithography

Stankevičius¹,

Gedvilas²,

Voisiat³

et al. 2013

Lith. J. Phys.

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The principles of the holographic lithography technique are reviewed, and the ability in the formation of structures with different periods by the holographic lithography technique in SZ2080 is demonstrated. The influence of laser exposure, phase shift between interfering laser beams, and the used laser wavelength on the structures fabricated by the four-beam interference technique has been studied. It is shown that by using the interfering beams with a different phase is it possible to reduce the period of the structure √ − 2 times compared to the four interfering beams of the same phase. Fabrication of micro-structures by the holographic lithography technique can be realized via multi-photon and single-photon polymerization processes. The structures created by these two techniques are compared. Finally, in the experiments with the five-beam interference, the doubleperiod effect was observed by adding the zero-order beam with a low intensity. The fabricated periodic microstructures have the potential to be used as a scaffold for cell growth and micro-optics.

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Section: Experimental Set-ups Of Holographic Lithography and Their Fementioning

confidence: 99%

Fabrication of periodic micro-structures by holographic lithography

Stankevičius¹,

Gedvilas²,

Voisiat³

et al. 2013

Lith. J. Phys.

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show abstract

“…In early work, Maznev et al showed that femtosecond pulses can be made to overlap by using 4f imaging of the +/-1 orders from a diffraction grating [5]. In the imaging process, the pulse fronts approach the crossing point so that there is even temporal overlap across the whole focal spot.…”

Section: High Intensity Pulse Front Matched Femtosecond Grating Formamentioning

confidence: 99%

Spatial chirp control of high-intensity 4D pulse focusing for laser-matter interactions

Durfee

Greco

Meier

et al. 2013

MATEC Web of Conferences

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Spatial chirp can be manipulated to control the focusing conditions for materials processing. Our double-ABCD nonparaxial analysis helps to understand and exploit the mechanisms for intensity localization, pulse front tilt, and grating formation, and includes initial spectral phase and detuning of the wavelength crossing plane. We also present a novel method for creating high density, high intensity interference patterns with crossed beams that have no relative pulse front tilt. Non-paraxial double ABCD tracingHigh-intensity laser-matter interactions inside a medium are complicated by nonlinear propagation along the way to the focal spot. Self-focusing, ionization defocusing and filamentation can prevent an ultrashort pulse from reaching its highest intensity. While focusing with high numerical aperture can suppress nonlinear propagation in advance of the focal plane, the area of the spot is necessarily on the scale of the wavelength. Control of the spatial distribution of the frequency components of an ultrafast pulse can lead to an axial localization of the intensity that is much smaller than the confocal parameter for the focal spot [1,2]. The technique of focusing spatially-chirped beams suppresses the intensity away from the focal plane, enabling our demonstration of micromachining on the backside of transparent materials [3,4]. Since the pulse duration gets shorter as the beam comes to a focus and the intensity is strongly localized in the axial direction, the pulse is effectively focused in 4D.The properties of space-time focused beams are strongly dependent of the nature of the spatial overlap of the frequency components. The analysis of optical systems with spatial chirp is therefore critical both for understanding the unusual properties of these beams and for designing systems to exploit these properties for materials processing. In a recent paper, we developed an analytical approach to calculate the propagation of spatially chirped beams. A ray is traced that represents the central axis of the Gaussian beamlet for each frequency component. Since one form of the calculation is nonparaxial, the beamlet angles can be large and the calculation is valid over a wider range of conditions than direct Fresnel propagation. Our technique explains, for example, how the evolution of the beamlet radius of curvature leads to an axial variation of the spectral chirp through the focus, contributing to the axial intensity localization. It also allows the derivation of simple scaling properties of the beam, showing that the improvement of the localization over the confocal parameter of the focused beamlets depends primarily on the degree of spatial chirp, not on the initial pulse duration or the focal length. General detuning of spatial chirped beams

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“…9 The practical implication of this limitation is that large samples cannot be simultaneously recorded by off-axis interferometry on the entire camera sensor using low-coherence sources. Diffractive gratings can solve this problem by tilting the field of the beams to be in plane, [9][10][11][12][13] with the cost of possible aliasing and image modulation.…”

Section: Introductionmentioning

confidence: 99%

Doubling the field of view in off-axis low-coherence interferometric imaging

2014

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We present a new interferometric and holographic approach, named interferometry with doubled imaging area (IDIA), with which it is possible to double the camera field of view while performing off-axis interferometric imaging, without changing the imaging parameters, such as the magnification and the resolution. This technique enables quantitative amplitude and phase imaging of wider samples without reducing the acquisition frame rate due to scanning. The method is implemented using a compact interferometric module that connects to a regular digital camera, and is useful in a wide range of applications in which neither the field of view nor the acquisition rate can be compromised. Specifically, the IDIA principle allows doubling the off-axis interferometric field of view, which might be narrower than the camera field of view due to low-coherence illumination. We demonstrate the proposed technique for scan-free quantitative optical thickness imaging of microscopic biological samples, including live neurons and a human sperm cell in rapid motion under high magnification. In addition, we used the IDIA principle to perform non-destructive profilometry during a rapid lithography process of transparent structures.

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How to make femtosecond pulses overlap

Cited by 182 publications

References 8 publications

Fabrication of periodic micro-structures by holographic lithography

Fabrication of periodic micro-structures by holographic lithography

Spatial chirp control of high-intensity 4D pulse focusing for laser-matter interactions

Doubling the field of view in off-axis low-coherence interferometric imaging

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