Flame focussing of laser beams and refractive fringe formation

Michaelis, M.M.; Bhagwandin, N.; Cunningham, P. F.

doi:10.1016/0030-4018(86)90331-7

Cited by 9 publications

(6 citation statements)

References 6 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…To understand the composite flame lens, one turns to conventional gas lens theory [1][2][3] and earlier flat flame experiments 16 , where the lens is modelled as a graded index medium established through the temperature (density) gradient transverse to the propagation. The refractive index, n, as a function of temperature, T, is taken to obey the Gladstone-Dale law for air 20 ,…”

Section: Resultsmentioning

confidence: 99%

“…The important point is that the central part of any flame is a poor refractor. Previous experiments 16 in which pencil beams were made to traverse a flat flame showed that the strongest refraction occurs at the flame front, followed by weakening refraction, as the pencil beam moves out of the flame's luminous sheath. This explains why only the light traversing the central regions of the spiral flame lens is refracted and not the peripheral.…”

Section: Discussionmentioning

confidence: 99%

“…There has also been interest in the optics of flames 10 , where the passive optical properties of flames have long been used in spectroscopy [10][11][12][13] , and flames have been used to line-focus laser light [14][15][16] . Optical devices based on gases and flames have the advantage of a high damage threshold.…”

mentioning

confidence: 99%

See 2 more Smart Citations

Focusing light with a flame lens

et al. 2013

View full text Add to dashboard Cite

The lens is a well-understood optical component used for focusing light, but is almost exclusively made in the solid-state form and, thus, suffers from optical damage at high powers. Attempts to overcome this through the use of non-solid graded-index media for lensing, for example, heated gasses, have found limited application owing to their long focal lengths. Here we describe the first flame lens, which produces a sharp focus with very little stray light and has a fourfold increase in focal power per unit length over previous gas lenses. Such gas devices remain topical due to their inherent ability to deliver high-power laser beams: our flame lens has a 'damage' threshold that is several orders of magnitude higher than that of most conventional lenses and is immediately repaired after damage for reuse, and thus will be of use in focusing high-irradiance laser beams.

show abstract

Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Focusing light with a flame lens

et al. 2013

View full text Add to dashboard Cite

show abstract

“…The study of these fringes has been extended to five types of refractive body by the authors and co-workers: flames (N Bhagwandin (2); glass microballoon laser fusion targets (0 Willi (3); laser plasmas on plane targets (R N Campbell (4,5)); spark induced shocks in air and compressed air shocks (R N Campbell, J Waltham); gas lenses (M Notcutt (6)). where L is the distance from the focus to the plane of observation The study of these fringes has been extended to five types of refractive body by the authors and co-workers: flames (N Bhagwandin (2); glass microballoon laser fusion targets (0 Willi (3); laser plasmas on plane targets (R N Campbell (4,5)); spark induced shocks in air and compressed air shocks (R N Campbell, 3 Waltham); gas lenses (M Notcutt (6)).…”

mentioning

confidence: 99%

“…Two types of refractive fringe technique are applicable : shadowgraphy and Schlieren. The former has been accomplished using a 50 ps probe beam to measure the plasma density in a shot to shot framing mode (2).…”

mentioning

confidence: 99%

Refractive Fringe Diagnostic Techniques

Michaelis¹,

Cunninghan²,

Campbell³

et al. 1987

SPIE Proceedings

View full text Add to dashboard Cite

Refractive fringes, were first observed by Evtushenko (1) et al.They are defined as intereference fringes caused by the interference of light refracted by an object either with other light refracted by the same object or with light that avoided the object by a small distance.The study of these fringes has been extended to five types of refractive body by the authors and co-workers: flames (N Bhagwandin (2); glass microballoon laser fusion targets (0 Willi (3); laser plasmas on plane targets (R N Campbell (4,5)); spark induced shocks in air and compressed air shocks (R N Campbell, J Waltham); gas lenses (M Notcutt (6)). FLAT FLAMES A long flat flame produced by a row of oxyacetylene nozzles, illustrates the formation of two types of refractive fringes, fine and coarse. Fine fringes occur when light penetrates the flame at a shallow depth and having been greatly refracted forms a line focus; light from the line focus interferes with unrefracted light to form a set of fringes spaced according to the relation ync (2n L ) where L is the distance from the focus to the plane of observation (Fig. la) Coarse fringes are formed by rays of different depths refracted from opposite sides of the narrow combustion front interfering with each other. These rays produce a fringe spacing obeying the Young double slit formula Y -L d SPIE Vol. 674 High Speed Photography (Pretoria 1986) / 531 REFRACTIVE FRINGE DIAGNOSTIC TECHNIQUES M M MICHAELIS, P F CUNNINGHAM, R N CAMPBELL M NOTCUTT AND 0 WALTHAM Refractive fringes, were first observed by Evtushenko (1) et al. They are defined as intereference fringes caused by the interference of light refracted by an object either with other light refracted by the same object or with light that avoided the object by a small distance.The study of these fringes has been extended to five types of refractive body by the authors and co-workers: flames (N Bhagwandin (2); glass microballoon laser fusion targets (0 Willi (3); laser plasmas on plane targets (R N Campbell (4,5)); spark induced shocks in air and compressed air shocks (R N Campbell, 3 Waltham); gas lenses (M Notcutt (6)). FLAT FLAMESA long flat flame produced by a row of oxyacetylene nozzles, illustrates the formation of two types of refractive fringes, fine and coarse. Fine fringes occur when light penetrates the flame at a shallow depth and having been greatly refracted forms a line focus; light from the line focus interferes with unrefracted light to form a set of fringes spaced according to the relation y n = (2n L )where L is the distance from the focus to the plane of observation ( Fig. la) Coarse fringes are formed by rays of different depths refracted from opposite sides of the narrow combustion front interfering with each other. These rays produce a fringe spacing obeying the Young double slit formula SPIE Vol. 674 High Speed Photography (Pretoria 1986) / 531 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/23/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx

show abstract