Beam shaping and high-speed, cylinder-lens-free beam guiding using acousto-optical deflectors without additional compensation optics

Bechtold, Peter; Hohenstein, R.; Schmidt, Michael

doi:10.1364/oe.21.014627

Cited by 31 publications

(14 citation statements)

References 18 publications

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“…The switching ratio in such a device is only limited by the time needed to reach a steady state in the actively emitting unit, which is in the 5 µs range for phosphorescent OLEDs 21 and even nanoseconds for fluorescent OLEDs 22 . High-speed beam-shaping solutions in the literature demonstrate switching velocities in the same regime or below (kHz - MHz) 23 – 25 . Characterization of the emission profile for the unit is carried out using a spectro-goniometer, where a detector measures the angular-dependent emission intensity.…”

Section: Resultsmentioning

confidence: 96%

Real-time beam shaping without additional optical elements

et al. 2018

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Providing artificial light and enhancing the quality of the respective light sources is of continued interest in the fields of solid state, condensed matter, and semiconductor physics. Much research has been carried out to increase the luminous efficiency, lifetime and colour stability of such devices. However, the emission characteristics of a given light source do not necessarily comply with today’s often sophisticated applications. Here, beam shaping addresses the transformation of a given light distribution into a customized form. This is typically achieved by secondary optical elements often sporting elaborate designs, where the actual light source takes up only a small fraction of the system’s volume. Such designs limit the final light source to a single permanent operation mode, which can only be overcome by employing mechanically adjustable optical elements. Here we show that organic light-emitting diodes (OLEDs) can enable real-time regulation of a beam shape without relying on secondary optical elements and without using any mechanical adjustment. For a red light-emitting two-unit OLED architecture, we demonstrate the ability to continuously tune between strongly forward and strongly sideward emission, where the device efficiency is maintained at an application-relevant level ranging between 6 and 8% of external quantum efficiency for any chosen setting. In combination with additional optical elements, customizable and tuneable systems are possible, whereby the tuning stems from the light source itself rather than from the use of secondary optics.

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Section: Resultsmentioning

confidence: 96%

Real-time beam shaping without additional optical elements

et al. 2018

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“…Moreover, a temporally focused low-NA Gaussian beam could be precisely positioned in a three-dimensional volume using a high-speed acoustic lens 59 , 78 – 81 or adding chromatic dispersion 82 . Alternatively, one could perform beam shaping by feeding the AODs with chirped signals (or multiple acoustic frequencies) 81 , 83 – 85 to create more power-efficient and axially confined light intensity patterns for optogenetic activation.…”

Section: Discussionmentioning

confidence: 99%

Optogenetic stimulation of complex spatio-temporal activity patterns by acousto-optic light steering probes cerebellar granular layer integrative properties

Hernandez

Pietrajtis

Mathieu

et al. 2018

Sci Rep

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Optogenetics provides tools to control afferent activity in brain microcircuits. However, this requires optical methods that can evoke asynchronous and coordinated activity within neuronal ensembles in a spatio-temporally precise way. Here we describe a light patterning method, which combines MHz acousto-optic beam steering and adjustable low numerical aperture Gaussian beams, to achieve fast 2D targeting in scattering tissue. Using mossy fiber afferents to the cerebellar cortex as a testbed, we demonstrate single fiber optogenetic stimulation with micron-scale lateral resolution, >100 µm depth-penetration and 0.1 ms spiking precision. Protracted spatio-temporal patterns of light delivered by our illumination system evoked sustained asynchronous mossy fiber activity with excellent repeatability. Combining optical and electrical stimulations, we show that the cerebellar granular layer performs nonlinear integration, whereby sustained mossy fiber activity provides a permissive context for the transmission of salient inputs, enriching combinatorial views on mossy fiber pattern separation.

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“…It should be noted that, during the transition from one frequency to the next, the angle of the deflected beam might be undefined. A work around for the latter is to synchronize the frequency switching with the pulse frequency of the laser beam, as demonstrated by Bechtold et al (2013a). As is clear from equations (4) and (5), the diffraction angle of an AOD depends of the wavelength of the laser beam.…”

Section: Acousto-optical Deflectorsmentioning

confidence: 99%

“…Therefore most approaches employ additional AODs inducing the inverse amount cylinder lensing (Bechtold et al, 2013a;Kirkby et al, 2010). However, Bechtold et al (2013a) developed a method to prevent cylindrical focusing effect, without compensationg optics, by acoustical frequency jumps synchronized to the pulse-to-pulse pause.…”

Section: Acousto-optical Deflectorsmentioning

confidence: 99%

Electro-optic and Acousto-optic Laser Beam Scanners

2014

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Optical solid state deflectors rely on the electro-optical or acousto-optic effect. These Electro-Optical Deflectors (EODs) and Acousto-Optical Deflectors (AODs) do not contain moving parts and therefore exhibit high deflection velocities and are free of drawbacks associated with mechanical scanners. A description of the principles of operation of EODs and AODs is presented. In addition, characteristics, properties and the (dis)advantages of EODs and AODs, when compared to mirror based mechanical deflectors, is discussed. Deflection angles, speed and accuracy are discussed in terms of resolvable spots and related quantities. Also, response time, damage threshold, efficiency and the type and magnitude of beam distortions is addressed. Optical deflectors are characterized by high angular deflection velocities, but small deflection angles. Whereas mechanical mechanical scanners are characterized by relatively small deflection velocities, but large deflection angles. Arranging an optical deflector and a mechanical scanner in series allows to take advantage of the best of both worlds.

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Beam shaping and high-speed, cylinder-lens-free beam guiding using acousto-optical deflectors without additional compensation optics

Cited by 31 publications

References 18 publications

Real-time beam shaping without additional optical elements

Real-time beam shaping without additional optical elements

Optogenetic stimulation of complex spatio-temporal activity patterns by acousto-optic light steering probes cerebellar granular layer integrative properties

Electro-optic and Acousto-optic Laser Beam Scanners

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