A narrow-band speckle-free light source via random Raman lasing

Hokr, Brett H.; Schmidt, Morgan S.; Bixler, Joel N.; Dyer, Phillip N.; Noojin, Gary D.; Redding, Brandon; Thomas, Robert J.; Rockwell, Benjamin A.; Cao, Hui; Yakovlev, Vladislav V.; Scully, Marlan O.

doi:10.1080/09500340.2015.1078919

Cited by 23 publications

(13 citation statements)

References 37 publications

(39 reference statements)

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“…mapped to what would otherwise be dark regions of the image increase the background level and lower the image contrast, the features of the object remain clearly visible. It has been shown in another experiment that even a narrow-band random laser, which has high temporal coherence, can provide speckle-free illumination for full-field imaging 80 .…”

Section: Speckle-free Imagingmentioning

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: Speckle-free Imagingmentioning

confidence: 99%

Complex lasers with controllable coherence

et al. 2019

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“…Speckle-free imaging with low spatial coherence light source is also an attractive area in imaging applications that can be used to further improve the imaging quality and break through the resolution limit. Random lasers (RLs) generated from lasing process in disordered medium have been demonstrated to intrinsically possess low spatial coherence which is suitable for speckle-free imaging [12][13][14][15]. However, the applications of RLs are limited by its poor emission directionality and low output power.…”

Section: Introductionmentioning

confidence: 99%

High-power low spatial coherence random fiber laser

Ma¹,

Li²,

Guo³

et al. 2019

Opt. Express

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A high-power multi-transverse modes random fiber laser (RFL) is investigated by combining a master oscillator power-amplifier (MOPA) configuration with a segment of extra-large mode area step-index multimode fiber (MMF). Spatial coherence of the highpower multi-transverse modes RFL has been analyzed, which shows that speckle contrast is reduced dramatically with the output power increasing. In this way, considerably low speckle contrast of ~0.01 is achieved under high laser power of ~56 W, which are the records for multi-transverse modes RFLs in both spatial coherence and output power. This work paves a way to develop high-power RFLs with very low spatial coherence for wide-range speckle-free imaging and free-space communication applications.

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“…Fast speckle suppression is essential for time-resolved imaging of moving targets or transient phenomena [10][11][12]. It can be achieved by using multimode lasers with low and tunable spatial coherence [13][14][15][16][17][18][19]. The decoherence time of such lasers, critical for fast speckle suppression in short integration times, is determined by the frequency spacing and linewidth of the individual lasing modes, as well as the total width of the emission spectrum ΔΩ [20].…”

Section: Introductionmentioning

confidence: 99%

Fast laser speckle suppression with an intracavity diffuser

et al. 2020

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Fast speckle suppression is crucial for time-resolved full-field imaging with laser illumination. Here, we introduce a method to accelerate the spatial decoherence of laser emission, achieving speckle suppression in the nanosecond integration time scale. The method relies on the insertion of an intracavity phase diffuser into a degenerate cavity laser to break the frequency degeneracy of transverse modes and broaden the lasing spectrum. The ultrafast decoherence of laser emission results in the reduction of speckle contrast to 3% in less than 1 ns.

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A narrow-band speckle-free light source via random Raman lasing

Cited by 23 publications

References 37 publications

Complex lasers with controllable coherence

Complex lasers with controllable coherence

High-power low spatial coherence random fiber laser

Fast laser speckle suppression with an intracavity diffuser

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