Bessel–like beams with z–dependent cone angles

Белый, В. Н.; Forbes, Andrew; Казак, Н. С.; Хило, Н. А.; Ропот, П. И.

doi:10.1364/oe.18.001966

Cited by 47 publications

(32 citation statements)

References 20 publications

(8 reference statements)

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“…The width of the front wave of top-hat-like profiles remained confined between 2 and 9 μm for distances up to 10 μm and the light intensity at the center of the wavefront decreased with the distance z as 1/z. These observations suggest that the tapered shape of these optical fibers act as optical components with properties reminiscent of conical lenses, called axicons (67) that transform a Gaussian into a Bessel beam (68,69). In some cases at the end of the experiment, we fully characterized the light exiting from the used TOF so to relate properties of the evoked photoresponse to the profile of the light impinging on the rod.…”

Section: Methodsmentioning

confidence: 99%

The phototransduction machinery in the rod outer segment has a strong efficacy gradient

Mazzolini

Facchetti

Andolfi

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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Rod photoreceptors consist of an outer segment (OS) and an inner segment. Inside the OS a biochemical machinery transforms the rhodopsin photoisomerization into electrical signal. This machinery has been treated as and is thought to be homogenous with marginal inhomogeneities. To verify this assumption, we developed a methodology based on special tapered optical fibers (TOFs) to deliver highly localized light stimulations. By using these TOFs, specific regions of the rod OS could be stimulated with spots of light highly confined in space. As the TOF is moved from the OS base toward its tip, the amplitude of saturating and single photon responses decreases, demonstrating that the efficacy of the transduction machinery is not uniform and is 5-10 times higher at the base than at the tip. This gradient of efficacy of the transduction machinery is attributed to a progressive depletion of the phosphodiesterase along the rod OS. Moreover we demonstrate that, using restricted spots of light, the duration of the photoresponse along the OS does not increase linearly with the light intensity as with diffuse light.V ertebrate photoreceptors, rods and cones, are morphologically specialized light sensing neurons and consist of four parts: an outer segment (OS), an inner segment (IS), the nuclear region, and the synapse (1). The OS of rod photoreceptors is stacked with thousands of lipid discs containing rhodopsin molecules that absorb photons (2-4). They are surrounded by a plasma membrane and differ in their lipid and protein composition.It is known that within 1 s, each excited rhodopsin, densely packed in the disc membrane, activates tens of G proteins (named transducin), each of which activates one phosphodiesterase (PDE) molecule (5-7). Activated PDEs rapidly hydrolyze cytoplasmic cyclic guanosine monophosphate (cGMP) thereby closing cyclic nucleotide-gated (CNG) channels (8, 9). In darkness, a current carried by Na + , K + , and Ca 2+ ions, which is known as the photocurrent, enters via the CNG channels into the OS and is pumped out by Na + /K + ATPase, located in the IS (1). This current can be recorded using suction electrodes (3, 10).The existence of distinct compartments on photoreceptor OSs is a consequence of their function. The OS is a highly modified nonmotile cilium developed for the absorption of light that is translated into the electrical signal. The IS and the nuclear region-containing the organelles and the nucleus-are dedicated to metabolism, homeostasis, and synthesis of the membrane and transportation of proteins and lipids supplied to the OS by an extensive trafficking through the tight restriction connecting the OS to the IS (11). Considering that, unlike typical cilia, the OS is continuously renewed throughout its entire life and given the varying density and asymmetry of the molecules involved, it is not surprising to find an efficacy gradient of phototransduction between the base and the tip. Indeed, the cholesterol (12, 13), the phospholipids (13-15), the CNG channels, the PDE (16), and the rhodop...

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Section: Methodsmentioning

confidence: 99%

The phototransduction machinery in the rod outer segment has a strong efficacy gradient

Mazzolini

Facchetti

Andolfi

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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“…Our results may be extended to higher azimuthal orders, to create Bessel-like beams that carry orbital angular momentum [23], by simply modulating the holograms with an appropriate azimuthally varying phase. There are however some limitations to these beams: the Bessel-like character is very accurate close to the center of the field and less accurate at the perimeter of the field, which can be rather complicated in structure as observed elsewhere [21]. This is also a characteristic of Bessel beams created with axicons.…”

Section: Discussionmentioning

confidence: 99%

“…Such beams have been created by complex multi-element set-ups (usually three or more) with free space propagation between them [20][21][22]. This makes the set-up difficult to align and prohibits the option of implementing the design with a thin phase-only solution, e.g., as a diffractive optic or with spatial light modulators.…”

Section: Introductionmentioning

confidence: 99%

Digital generation of shape-invariant Bessel-like beams

Litvin¹,

Mhlanga²,

Forbes³

2015

Opt. Express

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Bessel beams have been extensive studied to date but are always created over a finite region inside the laboratory. Means to overcome this consider multi-element refractive designs to create beams that have a longitudinal dependent cone angle, thereby allowing for a far greater quasi non-diffracting propagation region. Here we outline a generalized approach for the creation of shape-invariant Bessel-like beams with a single phase-only element, and demonstrate it experimentally with a phase-only spatial light modulator. Our experimental results are in excellent agreement with theory, suggesting an easy-to-implement approach for long range, shape-invariant Bessel-like beams.

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“…One efficient method is based on the laser excitation of sound in the media under study [10,11]. As was shown in [12][13][14][15], the use of different polarization modes of Bessel light beams (BLBs) as sound-exciting radiation [16] is promising for this method, because these beams have a number of unique properties (for example, they are not diffracted when they propagate in space [17][18][19]). An important specific feature of BLBs is the occurrence of a radial energy flux, which compensates for the change in the light-beam transversality when screened the beam central region [20].…”

Section: Introductionmentioning

confidence: 99%

Photoacoustic transformation of Bessel light beams in magnetoactive superlattices

et al. 2015

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Photoacoustic transformation of the TE mode of a Bessel light beam (BLB) has been studied for piezoelectric detection in short-period superlattices formed by magnetoactive crystals of bismuth germanate (Bi 12 GeO 20 ) and bismuth silicate (Bi 12 SiO 20 ) types. It is shown that the resulting signal amplitude can be controlled using optical schemes of BLB formation with a tunable cone angle. A resonant increase in the signal amplitude has been found in the megahertz range of modulation frequencies and its dependences on the BLB modulation frequency, geometric sizes of the two-layer structure and piezoelectric transducer, radial coordinate of the polarization BLB mode, and dissipative superlattice parameters are analyzed.

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Bessel–like beams with z–dependent cone angles

Cited by 47 publications

References 20 publications

The phototransduction machinery in the rod outer segment has a strong efficacy gradient

The phototransduction machinery in the rod outer segment has a strong efficacy gradient

Digital generation of shape-invariant Bessel-like beams

Photoacoustic transformation of Bessel light beams in magnetoactive superlattices

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