Experimental verification of the turbulent effects on laser beam propagation in space

Abstract

RESUMEN óíntegramente los efectos térmicos de un rayo láser que se propaga en el aire. Las mejoras incorporadas al diseño previo incluyeron un láser más potente, un sistema de formación de turbulencias de alta precisión, un sensor de presión integrado, y una plataforma para ajustar la altura entre el rayo láser y el modelo de turbulencia. Este diseño no sólo puede reproducir resultados previos con exactitud, sino que además permitió la medición exitosa de nuevos datos sobre la intensidad de la turbulencia C 2 n , la varianza de Rytov (cintilación) y el diámetro de coherencia (parámetro de Fried). Los interferogramas resultantes se analizaron utilizando transformadas rápidas de Fouse incrementan en relación con la temperatura. La región turbulenta mostró perturbaciones muy intensas, en el rango de 1.1 × 10 -12 m -2/3 a 2.7 × 10 -12 m -2/3 . A pesar de la intensidad de la turbulencia, con relación a la cintilación se demostró algo diferente, ya que la condición para un entorno de turbulencia débil se determinó en el laboratorio y se esperaba un bajo índice de cintilación. Esto es resultado de las distancias de propagación relativamente cortas obtenidas en el laboratorio. En la atmósfera abierta las trayectorias cubren grandes distancias y, para determinar los efectos de la turbulencia, el modelo debe generar turbulencias de mayor efectos térmicos de la turbulencia en un rayo láser en propagación. ABSTRACT beam propagating in air. Improvements made to the setup include a new, more powerful laser, a precision designed turbulence delivery system, an imbedded pressure sensor, and a platform for height adjustability between the laser beam and the turbulence model. The setup was not only able to reproduce previous results exactly but also allowed new data for the turbulence strength C 2 n , the Rytov variance (scintillation) and the coherence diameter (Fried's parameter) to be successfully measured. Analysis of the produced interferograms disturbances, in the range of 1.1 × 10 -12 m -2/3 to 2.7 × 10 -12 m -2/3 . In spite of the strong turbulence strength, scintillation proved otherwise, since the condition for a weak turbulence environment was determined in the laboratory and a low scintillation index was to be expected. This is as a result of the relatively short propagation distances achieved in the laboratory. In the open atmosphere, path lengths extend over vast distances and in order for turbulent effects to be realized, the turbulence model must generate stronger turbulence. The model was, therefore, able to demonstrate its ability to fully quantify and determine the thermal turbulence effects on a propagating laser beam.

The study of computational ghost imaging in presence of atmospheric turbulence

“…The Fresnel-Huygens diffraction equation has been used to investigate the theory of a plane wave beam diffracted from a turbulent medium. The transmission function of the object is named T(ζ) where T(ζ) is a simple shape like T. One can use the Fresnel integral to estimate the entanglement of the intensities (electric field) of SLM (𝐸 𝑠(𝑥) ) and the propagated field from SLM is given by [13]:…”

“…Turbulence-induced distortions cause blurring, speckle noise, and loss of spatial resolution [11,12]. These effects can severely limit the practical applications of CGI, particularly in long-range imaging scenarios [13]. By exploiting engineered structured illumination and adaptively adjusting to turbulent conditions, DCGI aims to provide improved imaging performance even in environments with varying vapor densities and turbulent characteristics [14].…”

Atmospheric propagation emulator for free space optical applications: design and performances

“…The wavefront deformation will lead to a variation of the light intensity at the end of the propagation path. According to Andrews and Phillips [1], [2], the refractive index structure coefficient -𝐶 𝑛 2 (commonly known as turbulence strength), can be calculated from Equation 1 as follows:…”

Analyzing the effect of oceanic turbulence on spreading properties of the Whittaker-Gaussian laser beam

“…Thus, research on random fluctuations such as biological tissues and atmospheric conditions is required. Therefore, the impact of laser beams traveling around various turbulence mediums have been extensively examined in various studies (Nossir et al 2021;Dalil-Essakali et al 2023;Chib et al 2022;Benzehoua and Belafhal 2023b;Ebrahim et al 2023;Augustine and Chetty 2014).…”