Study on the Difference of Wavefront Distortion on Beams Caused by Wavelength Differences in Weak Turbulence Region

Wu, Jiali; Ke, Xizheng; Kang, Weilong; Liang, Jingyuan; Ke, Chenghu

doi:10.3390/photonics10070725

Cited by 4 publications

(2 citation statements)

References 21 publications

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“…Further contributing to the understanding of wavefront variances, Ke derived a formula for the overall undulation variance in the wavefront for beams of different wavelengths, highlighting differences in wavefront variance under identical transmission conditions [13]. Finally, in 2023, Wu discussed the wavefront distortion differences among beams induced by wavelength disparities in weak turbulence regions [14].…”

Section: Introductionmentioning

confidence: 99%

Study on the Difference in Wavefront Distortion on Beams Caused by Wavelength Differences in the Strong Turbulence Region

Han,

Ke,

Liang

2024

Applied Sciences

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In free-space optical communication, the transmission of signal light and beacon light of differing wavelengths through the same atmospheric channel encounters variations in how the atmospheric refractive index absorbs and scatters light. This leads to distinct degrees of wavefront aberrations between the signal and beacon lights. In this study, we employed statistical optics to derive wavefront phase structure functions for both signal and beacon lights under conditions of strong turbulence. We explored how wavefront distortion varies among beams of different wavelengths after propagation through such turbulent conditions. Our findings revealed that as the turbulence outer scale escalates, the difference in wavefront distortion between signal and beacon lights stabilizes after an initial increase, assuming constant wavelengths. Furthermore, we observed significant changes in the relative wavefront aberrations when the inner scale of turbulence surpasses the separation between two points on the receiving apertures. As the disparity in wavelength decreases, so does the difference in wavefront aberrations. Finally, we propose a method for correcting wavefront aberrations based on coefficients of Zernike polynomials corresponding to beams with different wavelengths. This approach is validated through simulation and experimentation, demonstrating an 11% enhancement in the signal-to-optical Strehl ratio and a 0.072 increase in spot energy after the addition of correction coefficients compared with before their inclusion. These results solidify the efficacy of our method in improving adaptive optics correction accuracy.

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Section: Introductionmentioning

confidence: 99%

Study on the Difference in Wavefront Distortion on Beams Caused by Wavelength Differences in the Strong Turbulence Region

Han,

Ke,

Liang

2024

Applied Sciences

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“…In 2020, Ke derived the variance formula for different wavelength beams, and showed that there are differences on the wavefront aberration when different wavelength beams propagating through the same transmission conditions [8]. In 2023, Wu shows that after Gaussian beams of different wavelengths propagate through the same atmospheric channel, the cross-correlation number of the arrivalangle fluctuation decreases with an increase in the wavelength difference [9].…”

Section: Introductionmentioning

confidence: 99%

Beacon wavelength selection for wavefront detection in horizontal path under strong turbulence

Wu,

Zhong,

Wang

et al. 2023

Holography, Diffractive Optics, and Applications XIII

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Atmospheric turbulence has severe influence on laser beam propagations. The well accepted method of compensating for the aberrations in the turbulence is generating a beacon on the target or at the point-ahead location. In most scenarios, the wavelength of the beacon is similar to or shorter than the launched beam. However, when the strength of the turbulence gets stronger, intensity scintillations and wavefront branch points also arise, making it difficult to accurately measure the wavefront. As scintillations and branch points weakens with wavelength increases, it is reasonable to consider using beacons with longer wavelengths to improve wavefront detection accuracy. To further investigate the feasibility of beacons with longer wavelengths, we established a simulation model of wavefront detection and correction in horizontal path under strong turbulence. A split-step multi-phase screen method is employed to simulate the propagations of laser beams. Then a series of simulations with different refractive index structure parameter Cn2 and beacon wavelengths are studied. We show that under weak turbulence, the optimal wavelength of beacon is similar to the launched beam, as is widely investigated and concluded. However, beacons with longer wavelength are preferred under strong turbulence, especially with a general wavefront reconstruction algorithm without considering branch points. This research would be helpful to for designing adaptive optics systems to improve beam qualities in strong turbulence with adaptive optics systems.

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Phase Error Scaling Law in Two-Wavelength Adaptive Optics

Hyde,

Kalensky,

Spencer

2024

IEEE Photon. Technol. Lett.

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We derive a simple, physical, closed-form expression for the optical-path difference (OPD) of a two-wavelength adaptive-optics (AO) system. Starting from Hogge and Butts' classic OPD variance integral expression [J. Opt. Soc. Am. 72, 606 (1982)], we apply Mellin transform techniques to obtain series and asymptotic solutions to the integral. For realistic twowavelength AO systems, the former converges slowly and has limited utility. The latter, on the other hand, is a simple formula in terms of the separation between the AO sensing (i.e., the beacon) and compensation (or observation) wavelengths. We validate this formula by comparing it to the OPD variances obtained from the aforementioned series and direct numerical evaluation of Hogge and Butts' integral. Our simple asymptotic expression is shown to be in excellent agreement with these exact solutions. The work presented in this paper will be useful in the design and characterization of two-wavelength AO systems.

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Study on the Difference of Wavefront Distortion on Beams Caused by Wavelength Differences in Weak Turbulence Region

Cited by 4 publications

References 21 publications

Study on the Difference in Wavefront Distortion on Beams Caused by Wavelength Differences in the Strong Turbulence Region

Study on the Difference in Wavefront Distortion on Beams Caused by Wavelength Differences in the Strong Turbulence Region

Beacon wavelength selection for wavefront detection in horizontal path under strong turbulence

Phase Error Scaling Law in Two-Wavelength Adaptive Optics

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