Separation of coherent and incoherent light by using optical vortex via spatial mode projection

Li, Xiang; Wang, X.; Yi, Yang; Zhou, Yifan; Chen, Qianyuan; Wang, Anzhou; Mao, Song; Yan, Yuqi

doi:10.1016/j.optcom.2022.128986

Cited by 5 publications

(5 citation statements)

References 34 publications

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“…Such an application would be unlikely to be beneficial in most freespace LIDAR applications, where forward scatter makes up a relatively small fraction of the noise. In [3], "Numerical simulation model of an optical filter using an optical vortex", it is unclear how they were able to achieve the improvement using a Fresnel lens mask on the SLM. As discussed earlier, a Fresnel lens exploits refraction rather than interference to produce its focussing effect.…”

Section: Discussionmentioning

confidence: 99%

“…Another paper that describes a spatial coherence filter is "Numerical simulation model of an optical filter using an optical vortex" by Zhou et al [3]. In their work, they utilise a spatial light modulator (SLM) with a phase map that will impart a topological charge onto the beam, forming a ring-shaped Laguerre-Gaussian (LG) beam if the incident light is coherent, and experiencing no significant change if the light is incoherent.…”

Section: Literaturementioning

confidence: 99%

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The practicalities of a spatial coherence filter in free-space LIDAR environments

Hawthorne,

McDonald,

Park

et al. 2023

Electro-Optical and Infrared Systems: Technology and Applications XX

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A scanning LIDAR system that uses a single pixel detector can be highly attractive, with simple data processing coupled with low cost and complexity. However, the impact of ambient light noise is much greater than with a multiple pixel system. A potential means of overcoming this is to filter for transverse spatial coherence. Such filters have been discussed and evaluated in the literature, typically based on an axicon or a spiral phase plate that creates a ring with coherent light. Incoherent light, in contrast, smears the light out diffusely, allowing for spatial separation and thus, filtering. The focus of the existing literature tends to be in optical communication or underwater ranging, whereas a free-space LIDAR environment has distinct issues that inhibit the practicality of the filter if a direct replication is performed. This work thus focusses on exploring the practical implementation of these filters in a free-space LIDAR environment.

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Section: Discussionmentioning

confidence: 99%

Section: Literaturementioning

confidence: 99%

The practicalities of a spatial coherence filter in free-space LIDAR environments

Hawthorne,

McDonald,

Park

et al. 2023

Electro-Optical and Infrared Systems: Technology and Applications XX

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“…Changes in spatial coherence have been exploited to improve transmission measurements, primarily using optical vortices [5][6][7] . Optical vortices are produced when an input Gaussian beam is encoded with an orbital angular momentum (OAM), which can be done using a phase plate, creating an intensity ring about a null centre 8 .…”

Section: Optical Vortex-based Transmissometersmentioning

confidence: 99%

“…These signals can then be separated, either using image processing techniques 5 or by introducing additional optics prior to signal detection. For example, Li et al (2022) created enhanced spatial separation between the coherent and incoherent light by imparting a large OAM mode and focusing the beam down such that the incoherent light formed a spot in the center of the coherent ring 6 . Watnik et al (2023) simulated a scheme that could minimize the effect of scattered light on the transmitted signal by placing a beam block after the phase plate, designed to block out the spatially incoherent portion while allowing the spatially coherent light to pass through and be focused via lens onto a detector 7 .…”

Section: Optical Vortex-based Transmissometersmentioning

confidence: 99%

Optimizing beam attenuation measurements using spatial incoherence

Gribbon¹,

McKee²,

Griffin³

2023

Ocean Sensing and Monitoring XV

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The beam attenuation coefficient is a fundamental inherent optical property (IOP) and accurate measurements of attenuation are necessary for input to radiative transfer models. Transmissometers for measuring attenuation are systematically biased by inadvertently collecting light that is scattered in forwards directions within the collection angle of the instrument. Recent experimental work has demonstrated the splitting of coherent, transmitted light into optical vortex modes, leaving the incoherent, forward-scattered light in the vortex null (Alley et al., 2018). We propose that a linear diffraction grating can be used to spatially separate a portion of coherent, unscattered light. We demonstrate experimentally a coherence transmissometer using this concept and compare its performance against that of a standard transmissometer using a traditional lens and pinhole arrangement.

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“…Hence, vortex beams can serve as carriers for coherence-based filtering, achieving spatial separation between coherent and incoherent light. 5 The fundamental principle involves emitting Gaussian laser beam and modulating the received signals through optical field modulation. Echo beams with coherence (signal light) can be modulated into vortex beams, while echo beams lacking coherence (multi-scattered light, background light) remain unmodulated, retaining Gaussian geometrical distribution.…”

Section: Introductionmentioning

confidence: 99%

A method to enhance the detection capability of optical sensing based on the quantum characteristics of vortex beam

Li,

Zhang,

et al. 2023

Quantum and Nonlinear Optics X

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We propose a method based on vortex beams, which carries optical orbital angular momentum (OAM) to achieve spatial separation of coherent signal light and incoherent noise light and conducted experiments to evaluate the effect. Based on the experimental results, we established the relationship between signal-to-noise ratio (SNR) and topological charge number, signal channel size, and then optimized the relevant parameters. We built a LIDAR system for underwater detection to verify the practical effectiveness of the method. The experimental results demonstrate a significant improvement in the SNR for underwater detection.

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Separation of coherent and incoherent light by using optical vortex via spatial mode projection

Cited by 5 publications

References 34 publications

The practicalities of a spatial coherence filter in free-space LIDAR environments

The practicalities of a spatial coherence filter in free-space LIDAR environments

Optimizing beam attenuation measurements using spatial incoherence

A method to enhance the detection capability of optical sensing based on the quantum characteristics of vortex beam

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