Manipulating the spatial coherence of a laser source

Chriki, Ronen; Nixon, Micha; Pal, Vishwa; Tradonsky, Chene; Barach, Gilad; Friesem, Asher A.; Davidson, Nir

doi:10.1364/oe.23.012989

Cited by 40 publications

(13 citation statements)

References 31 publications

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“…A further manipulation of the spatial coherence properties is obtained by resorting to more sophisticated intra-cavity spatial filters (masks) in the degenerate cavity laser 67 . For example, a variable slit which enables independent control of the spatial coherence length in one coordinate axis without affecting that in the other axis; two pinholes, an annular band and an array of circular holes can generate cosine, Bessel and comb-like spatial coherence functions, respectively.…”

Section: Degenerate Cavity Lasermentioning

confidence: 99%

Complex lasers with controllable coherence

et al. 2019

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The invention of lasers 60 years ago is one of the greatest breakthroughs in modern optics. Throughout the years, lasers have enabled major scientific and technological advancements, and have been exploited in numerous applications due to their advantages such as high brightness and high coherence. However, the high spatial coherence of laser illumination is not always desirable, as it can cause adverse artifacts such as speckle noise in imaging applications. To reduce the spatial coherence of a laser, novel cavity geometries and alternative feedback mechanisms have been developed. By tailoring the spatial and spectral properties of cavity resonances, the number of lasing modes, the emission profiles and the coherence properties can be controlled. This technical review presents an overview of such unconventional, complex lasers, with a focus on their spatial coherence properties. Laser coherence control not only provides an efficient means for eliminating coherent artifacts, but also enables new applications.

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Section: Degenerate Cavity Lasermentioning

confidence: 99%

Complex lasers with controllable coherence

et al. 2019

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“…The modal frequency spectrum with separation of time scales is also similar to that of multimode fiber lasers that are not extremely long (typical length 100 m). We therefore see a general link between the near degeneracy of the spatial modes in gain and loss (enabling support of many spatial modes even in the presence of mode competition [17,47]) and their near degeneracy in frequency.…”

Section: Modal Frequency Spectrum Analysismentioning

confidence: 84%

Spatiotemporal supermodes: Rapid reduction of spatial coherence in highly multimode lasers

et al. 2018

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Spatial coherence quantifies spatial field correlations over time, and is one of the fundamental properties of light. Here we investigate the spatial coherence of highly multimode lasers in the regime of short time scales. Counter intuitively, we show that in this regime, the temporal (longitudinal) modes play a crucial role in spatial coherence reduction. To evaluate the spatial coherence we measured the temporal dynamics of speckle fields generated by a highly multimode laser with over 10 5 lasing spatial (transverse) modes, and examined the dependence of speckle contrast on the exposure time of the detecting device. We show that in the regime of short time scale, the spatial and temporal modes interact to form spatio-temporal supermodes, such that the spatial degrees of freedom are encoded onto the temporal modes. As a result, the speckle contrast depends on the number of temporal modes, and the degree of spatial coherence is reduced and the speckle contrast is suppressed. In the regime of long times scale, the supermodes are no longer a valid representation of the laser modal structure. Consequently, the spatial coherence is independent of the temporal modes, and the classical result, where the speckle contrast is suppressed as the number of spatial modes, is obtained. Due to this new spatio-temporal mechanism, highly multimode lasers can be used for speckle suppression in high-speed full-field imaging applications, as we demonstrate here for imaging of a fast moving object.

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“…Either an LED or a laser can be employed once their spatial coherence is properly controlled, yielding a 1D coherent beam. It is promising to use a laser with tunable spatial coherence [23] such as degenerate cavity lasers [24]. Our simple approach has potential for advancing LSFM systems [25], including generation of multiple light-sheets in 3D [26,27].…”

Section: Discussionmentioning

confidence: 99%