Encyclopedia of Optical Engineering

Burillo, Francisco Rocadenbosch

doi:10.1081/e-eoe

Cited by 16 publications

(4 citation statements)

References 66 publications

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“…435 where w 0 is the original waist of the beam, x is the distance along the optical path, λ is the wavelength of light, and n is the index of refraction [41]. Calculation considers G = 100, R = 100 Ω, κ = 0.119 A/W, P = 133 mW, d = 6 mm, t = 0.25 440 mm, w 0 = 0.5 mm, λ= 6.8 mm, δ= 1 nm.…”

Section: Resultsmentioning

confidence: 99%

Non-Contact Ultrasonic Inspection by Gas-Coupled Laser Acoustic Detection (GCLAD)

Gulino

Bruzzi

Caron

et al. 2021

Preprint

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Gas-Coupled Laser Acoustic Detection (GCLAD) is an ultrasonic, non-contact detection technique that has been recently proven to be applicable to the inspection of mechanical components. GCLAD response raises as the intersection length between the probe laser beam and the acoustic wavefront propagating in the air increases; such feature differentiates the GCLAD device from other optical detection instruments, making it a line detection system rather than a point detector. During the inspection of structures mainly extending in two dimensions, the capability to evidence presence of defects in whichever point over a line would enable moving the emitter and the detector along a single direction: this translates in the possibility to decrease the overall required time for interrogation of components compared to point detectors, as well as generating simpler automated monitoring layouts. Based on this assumption, the present study highlights the possibility of employing the GCLAD device as a line inspection tool. To this end, preliminary concepts are provided allowing maximization of the GCLAD response for the non-destructive testing of components which predominantly extend in two dimensions. Afterwards, the GCLAD device is employed in pulse-echo mode for the detection of artificial defects machined on a 12 mm-thick steel plate: the GCLAD probe laser beam is inclined to be perpendicular to the propagation direction of the airborne ultrasound, generated by surface acoustic waves (SAWs) in the solid which are first reflected by the defect flanks and subsequently refracted in the air. Numerical results are provided highlighting the SAW reflection patterns, originated by 3 mm deep surface and subsurface defects, that the GCLAD should interpret. The subsequent experimental campaign highlights that the GCLAD device can identify echoes associated with surface and subsurface defects, located in eight different positions on the plate. B-scan of the component ultimately demonstrates the GCLAD performance in accomplishing the inspection task.

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Section: Resultsmentioning

confidence: 99%

Non-Contact Ultrasonic Inspection by Gas-Coupled Laser Acoustic Detection (GCLAD)

Gulino

Bruzzi

Caron

et al. 2021

Preprint

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“…A major advantage in using these LCs is that, despite their high rotational viscosity, they exhibit a fast response time to an applied electric field. The threshold voltage, V th at which the LC starts to respond to the external applied voltage is directly related to the dielectric anisotropy and can be described as (Spring, 2011):…”

Section: B Electric Tunabilitymentioning

confidence: 99%

“…Therefore, as the dielectric anisotropy, ∆ε increases, the LC responds to lower applied voltages. It should be emphasized that other factors such as the rise and decay times, elastic constants, Frederick's transition of the LCs also play a role in the final performance of the LC-based devices (Onuki, 2004;Spring, 2011).…”

Section: B Electric Tunabilitymentioning

confidence: 99%

“…New guiding mechanisms were thus essential in order to minimize or even eliminate these effects. One such early attempt was the idea of using an air-glass microstructure for optical fiber guidance; proposed and demonstrated by Standley and Holden (1974) and Kaiser and Astle (1974). Although unsuccessful, this work would be reinvented with great success a few decades later.…”

Section: Introduction a Historical Backgroundmentioning

confidence: 99%

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Hybrid photonic-crystal fiber

Markos,

Travers,

Abdolvand

et al. 2019

Preprint

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This article offers an extensive survey of results obtained using hybrid photonic crystal fibers (PCFs) which constitute one of the most active research fields in contemporary fiber optics. The ability to integrate novel and functional materials in solid-and hollow-core PCFs through various post-processing methods has enabled new directions towards understanding fundamental linear and nonlinear phenomena as well as novel application aspects, within the fields of optoelectronics, material and laser science, remote sensing and spectroscopy. Here the recent progress in the field of hybrid PCFs is reviewed from scientific and technological perspectives, focusing on how different fluids, solids and gases can significantly extend the functionality of PCFs. In the first part of this review we discuss the most important efforts by research groups around the globe to develop tunable linear and nonlinear fiber-optic devices using PCFs infiltrated with various liquids, glasses, semiconductors and metals. The second part is concentrated on the most recent and state-of-the-art advances in the field of gasfilled hollow-core PCFs. Extreme ultrafast gas-based nonlinear optics towards light generation in the extreme wavelength regions of vacuum ultraviolet (VUV), pulse propagation and compression dynamics in both atomic and molecular gases, and novel soliton -plasma interactions are reviewed. A discussion of future prospects and directions is also included.

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3D‐ultramicroscopy utilizing aspheric optics

Saghafi

Becker

Hahn

et al. 2013

Journal of Biophotonics

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Using a combination of achromatic aspheric optical elements and achromatic cylindrical lenses, we developed an improved laser light sheet generator for two-side illumination ultramicroscopy. This light sheet generator has a much longer Rayleigh range, a more uniform spatial intensity distribution along x -, y - and z-axis, and reduced aberrations than the standard system consisting of a slit aperture and a single cylindrical lens, which is commonly used in light sheet microscopy. As there is no truncation of the beam by a slit aperture in our design the laser energy is used more efficiently. Applying this light sheet generator to ultramicroscopy of chemically cleared biological samples, such as Drosophila, dissected mouse hippocampi, and entire mouse brains, we achieved a markedly improved resolution of fine details.

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Encyclopedia of Optical Engineering

Cited by 16 publications

References 66 publications

Non-Contact Ultrasonic Inspection by Gas-Coupled Laser Acoustic Detection (GCLAD)

Non-Contact Ultrasonic Inspection by Gas-Coupled Laser Acoustic Detection (GCLAD)

Hybrid photonic-crystal fiber

3D‐ultramicroscopy utilizing aspheric optics

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