Dr. Italo Toselli is the founding member of TurbOttica LLC and a senior scientist at Fraunhofer IOSB. He has received his M.Sc. degree (2002) in Electronics Engineering from La Sapienza University (Italy) and his postgraduate Master in Information Technology (2002) from Cefriel-Politecnico di Milano (Italy) followed by his Ph.D. (2008) in Electronics and Communication Engineering from Politecnico di Torino (Italy). Before starting his Ph.D., he joined the Italian Navy as an Officer. During his Ph.D., he spent more than two years at the University of Central Florida, Orlando, working with Profs. Larry C. Andrews and Ronald L. Phillips. From January 2010 to October 2011 he held a National Research Council postdoctoral award at the Department of Mechanical and Aerospace Engineering, Naval Postgraduate School, Monterey, California. From September 2013 to June 2014 he was an ERCIM Marie Curie Fellow at the same institute where he is currently employed (Fraunhofer IOSB). From June 2014 to May 2017 he was a researcher at the Department of Physics at the University of Miami, Florida, before eventually re-joining Fraunhofer IOSB. Dr. Toselli co-authored more than 50 journal and proceeding papers focused on laser beam propagation through random media and he is a reviewer of main journals in optics and atmospheric propagation. He has served as invited speaker at SPIE and OSA conferences. He is a Senior member of OSA, a member of SPIE and a Committee member of main conferences in his field.
We discuss the capability of adaptive optics to increase the performance of laser systems operati... more We discuss the capability of adaptive optics to increase the performance of laser systems operating in atmospheric turbulence. Our approach is based on the Zernike filter functions, Taylor's frozen-flow hypothesis, and bandwidth limitations of a realistic servo control system. System performance is analyzed in terms of the Strehl ratio on target. Our results for plane-wave geometry indicate that adaptive optics can be effective even when engaging fast moving targets and that moderate closed-loop bandwidths of ∼100Hz would suffice for most analyzed scenarios. Applications of interest are beam delivery systems and free-space optical communications.
We investigate theoretically the performance of adaptive-optics correction for Gaussian beams aff... more We investigate theoretically the performance of adaptive-optics correction for Gaussian beams affected by oceanic turbulence. Action of adaptive optics is modeled as removal of a certain number of Zernike modes from the aberrated wavefront. We found that, similarly to atmospheric turbulence, adaptive optics is very effective in improving optical system performance of laser communication links in weak oceanic turbulence.
The presence of anisotropic turbulence statistics within the first meter from the ground surface ... more The presence of anisotropic turbulence statistics within the first meter from the ground surface has been known for decades from optical beam propagation experiments. We have carried over a number of measurements of a single lowest-order Gaussian He-Ne laser beam propagating close to the terrain. The experiments took place on the grounds of the University of Miami, FL over a grassy field in a variety of meteorological conditions and at a number of different heights from the ground. The spatial-temporal fluctuations of the intensity of a slightly divergent beam were recorded by a CCD camera and analyzed by the statistical moment calculations. The beam statistics were used for inferring the parameters of turbulent anisotropy, such as the ellipticity and the orientation of the refractive index anisotropy ellipse. Our results indicate that along the sub-kilometer link the two-point intensity correlation function of the beam manifests evident anisotropic features (anisotropic factors and...
ABSTRACT It is well known that in free atmosphere the Kolmogorov power spectrum of the refractive... more ABSTRACT It is well known that in free atmosphere the Kolmogorov power spectrum of the refractive index might not properly describe the actual turbulence behavior. In this paper, we use general non-Kolmogorov power spectrum for theoretical investigation of laser beam propagation in the double-passage problem: transmitter–target–receiver. The major application of our work is the Light Detection And Ranging (LIDAR) system operating at high altitudes, where non-Kolmogorov turbulence may be present. On confining ourselves to the weak turbulence regime, we show that the long-term average beam intensity profile, the long-term beam spread and the scintillation index are substantially affected by the non-Kolmogorov turbulent channels. Our analysis is valid for both bi-static and mono-static configurations, the latter leading to the enhanced backscattering effects.
Atmospheric turbulence induces significant variation on the angle-of-arrival of laser beams used ... more Atmospheric turbulence induces significant variation on the angle-of-arrival of laser beams used in free space laser communication. Angle-of-arrival fluctuations of an optical wave in the plane of the receiver aperture can be described in terms of the phase structure function that already has been calculated by Kolmogorov's power spectral density model. Unfortunately several experiments showed that Kolmogorov theory is sometimes incomplete to describe atmospheric statistics properly. In this paper, for horizontal path and weak turbulence, we carry out analysis of angle-of-arrival fluctuations using a non Kolmogorov power spectrum which uses a generalized exponent factor instead of constant standard exponent value 11/3 and a generalized amplitude factor instead of constant value 0.033. Also our non Kolmogorov spectrum includes both inner scale and outer scale effects.
Experimental and theoretical work has shown that atmospheric turbulence can exhibit "non-Kol... more Experimental and theoretical work has shown that atmospheric turbulence can exhibit "non-Kolmogorov" behavior including anisotropy and modifications of the classically accepted spatial power spectral slope, -11/3. In typical horizontal scenarios, atmospheric anisotropy implies that the variations in the refractive index are more spatially correlated in both horizontal directions than in the vertical. In this work, we extend Gaussian beam theory for propagation through Kolmogorov turbulence to the case of anisotropic turbulence along the horizontal direction. We also study the effects of different spatial power spectral slopes on the beam propagation. A description is developed for the average beam intensity profile, and the results for a range of scenarios are demonstrated for the first time with a wave optics simulation and a spatial light modulator-based laboratory benchtop counterpart. The theoretical, simulation, and benchtop intensity profiles show good agreement and ...
It is well known that free space laser system performance is limited by atmospheric turbulence. M... more It is well known that free space laser system performance is limited by atmospheric turbulence. Most theoretical treatments have been described for many years by Kolmogorov's power spectral density model because of its simplicity. Unfortunately several experiments have been reported recently that show the Kolmogorov theory is sometimes incomplete to describe atmospheric statistics properly, in particular, in portions of the troposphere and stratosphere. In this paper, using a non Kolmogorov spectrum and following same procedure already used for horizontal path analysis, we extend free space optical system performance analysis to uplink and downlink paths. Our non Kolmogorov spectrum uses a generalized exponent instead of constant standard exponent value 11/3 and a generalized amplitude factor instead of constant value 0.033. Therefore, in non-Kolmogorov weak turbulence, we carry out, for a uplink and a downlink paths, analysis of Long Term Beam Spread, Scintillation index, Proba...
We use the general non-Kolmogorov power spectrum for theoretical investigation of double-passage ... more We use the general non-Kolmogorov power spectrum for theoretical investigation of double-passage propagation of Gaussian beams in deep turbulence for the case of a point target. The presented results are of interest in LIDARs operating at high altitude, where non-Kolmogorov turbulence may be present.
Theoretical models and results of experimental campaigns relating to non-classic regimes occurrin... more Theoretical models and results of experimental campaigns relating to non-classic regimes occurring in atmospheric optical turbulence are overviewed. Non-classic turbulence may manifest itself through such phenomena as a varying power law of the refractive-index power spectrum, anisotropy, the presence of constant-temperature gradients and coherent structures. A brief historical introduction to the theories of optical turbulence, both classic and non-classic, is first presented. The effects of non-classic atmospheric turbulence on propagating light beams are then discussed, followed by the summary of results on measuring the non-classic turbulence, on its computer and in-lab simulations and its controlled synthesis. The general theory based on the extended Huygens–Fresnel method, capable of quantifying various effects of non-classic turbulence on propagating optical fields, including the increased light diffraction, beam profile deformations, etc., is then outlined. The review conclu...
Abstract. We use a non-Kolmogorov power spectrum for theoretical investigation of laser beam prop... more Abstract. We use a non-Kolmogorov power spectrum for theoretical investigation of laser beam propagation in the double-passage problem: transmitter–target–receiver. The major application of our work is the light detection and ranging (LIDAR) system operating in the zone of the atmosphere where non-Kolmogorov turbulence may be present. We show that the scintillation index is substantially affected by non-Kolmogorov turbulent channels at any turbulence strength. We consider the case of a small unresolved target and our analysis is valid for both the bistatic and monostatic configuration of the LIDAR system, in which the latter leads to the enhanced backscattering effects. Additionally, the paper contains a discussion of the simulation approach to light propagation through non-Kolmogorov turbulence. The simulation results and a discussion of their agreement with the theory are included. We found that the theory and the results of the simulations agree only to a certain extent. The “giant spikes” that occur when propagating through “deep turbulence” are responsible for the lack of better agreement. Their influence on the scintillation index and also on the probability density function of intensity probably requires a theoretical approach.
An experimental study has been performed of a laser beam propagating horizontally through the nea... more An experimental study has been performed of a laser beam propagating horizontally through the near-ground atmosphere above a grassy field at the University of Miami (UM) Coral Gables campus. The average intensity, scintillation index, and intensity correlation function are measured in the receiver plane for three channels with different turbulent conditions and at three different heights above the ground. Our results reveal that along short links (210 m) only the intensity correlation function captures the anisotropic information of turbulence, corresponding to the refractive index anisotropy ellipse of atmospheric fluctuations. In addition, we report an interesting phenomenon relating to turbulence eddy orientation near the ground. We confirmed that the experimental results are in agreement with the numerical simulations based on the multiple phase-screen method. Our findings provide an efficient method of determining the anisotropic parameters of atmospheric turbulence.
Atmospheric turbulence simulator is built and characterized for in-lab optical wave propagation w... more Atmospheric turbulence simulator is built and characterized for in-lab optical wave propagation with controlled strength of the refractive-index fluctuations. The temperature gradients are generated by a sequence of heat guns with controlled individual strengths. The temperature structure functions are measured in two directions transverse to propagation path with the help of a thermocouple array and used for evaluation of the corresponding refractive-index structure functions of optical turbulence.
We discuss the capability of adaptive optics to increase the performance of laser systems operati... more We discuss the capability of adaptive optics to increase the performance of laser systems operating in atmospheric turbulence. Our approach is based on the Zernike filter functions, Taylor's frozen-flow hypothesis, and bandwidth limitations of a realistic servo control system. System performance is analyzed in terms of the Strehl ratio on target. Our results for plane-wave geometry indicate that adaptive optics can be effective even when engaging fast moving targets and that moderate closed-loop bandwidths of ∼100Hz would suffice for most analyzed scenarios. Applications of interest are beam delivery systems and free-space optical communications.
We investigate theoretically the performance of adaptive-optics correction for Gaussian beams aff... more We investigate theoretically the performance of adaptive-optics correction for Gaussian beams affected by oceanic turbulence. Action of adaptive optics is modeled as removal of a certain number of Zernike modes from the aberrated wavefront. We found that, similarly to atmospheric turbulence, adaptive optics is very effective in improving optical system performance of laser communication links in weak oceanic turbulence.
The presence of anisotropic turbulence statistics within the first meter from the ground surface ... more The presence of anisotropic turbulence statistics within the first meter from the ground surface has been known for decades from optical beam propagation experiments. We have carried over a number of measurements of a single lowest-order Gaussian He-Ne laser beam propagating close to the terrain. The experiments took place on the grounds of the University of Miami, FL over a grassy field in a variety of meteorological conditions and at a number of different heights from the ground. The spatial-temporal fluctuations of the intensity of a slightly divergent beam were recorded by a CCD camera and analyzed by the statistical moment calculations. The beam statistics were used for inferring the parameters of turbulent anisotropy, such as the ellipticity and the orientation of the refractive index anisotropy ellipse. Our results indicate that along the sub-kilometer link the two-point intensity correlation function of the beam manifests evident anisotropic features (anisotropic factors and...
ABSTRACT It is well known that in free atmosphere the Kolmogorov power spectrum of the refractive... more ABSTRACT It is well known that in free atmosphere the Kolmogorov power spectrum of the refractive index might not properly describe the actual turbulence behavior. In this paper, we use general non-Kolmogorov power spectrum for theoretical investigation of laser beam propagation in the double-passage problem: transmitter–target–receiver. The major application of our work is the Light Detection And Ranging (LIDAR) system operating at high altitudes, where non-Kolmogorov turbulence may be present. On confining ourselves to the weak turbulence regime, we show that the long-term average beam intensity profile, the long-term beam spread and the scintillation index are substantially affected by the non-Kolmogorov turbulent channels. Our analysis is valid for both bi-static and mono-static configurations, the latter leading to the enhanced backscattering effects.
Atmospheric turbulence induces significant variation on the angle-of-arrival of laser beams used ... more Atmospheric turbulence induces significant variation on the angle-of-arrival of laser beams used in free space laser communication. Angle-of-arrival fluctuations of an optical wave in the plane of the receiver aperture can be described in terms of the phase structure function that already has been calculated by Kolmogorov's power spectral density model. Unfortunately several experiments showed that Kolmogorov theory is sometimes incomplete to describe atmospheric statistics properly. In this paper, for horizontal path and weak turbulence, we carry out analysis of angle-of-arrival fluctuations using a non Kolmogorov power spectrum which uses a generalized exponent factor instead of constant standard exponent value 11/3 and a generalized amplitude factor instead of constant value 0.033. Also our non Kolmogorov spectrum includes both inner scale and outer scale effects.
Experimental and theoretical work has shown that atmospheric turbulence can exhibit "non-Kol... more Experimental and theoretical work has shown that atmospheric turbulence can exhibit "non-Kolmogorov" behavior including anisotropy and modifications of the classically accepted spatial power spectral slope, -11/3. In typical horizontal scenarios, atmospheric anisotropy implies that the variations in the refractive index are more spatially correlated in both horizontal directions than in the vertical. In this work, we extend Gaussian beam theory for propagation through Kolmogorov turbulence to the case of anisotropic turbulence along the horizontal direction. We also study the effects of different spatial power spectral slopes on the beam propagation. A description is developed for the average beam intensity profile, and the results for a range of scenarios are demonstrated for the first time with a wave optics simulation and a spatial light modulator-based laboratory benchtop counterpart. The theoretical, simulation, and benchtop intensity profiles show good agreement and ...
It is well known that free space laser system performance is limited by atmospheric turbulence. M... more It is well known that free space laser system performance is limited by atmospheric turbulence. Most theoretical treatments have been described for many years by Kolmogorov's power spectral density model because of its simplicity. Unfortunately several experiments have been reported recently that show the Kolmogorov theory is sometimes incomplete to describe atmospheric statistics properly, in particular, in portions of the troposphere and stratosphere. In this paper, using a non Kolmogorov spectrum and following same procedure already used for horizontal path analysis, we extend free space optical system performance analysis to uplink and downlink paths. Our non Kolmogorov spectrum uses a generalized exponent instead of constant standard exponent value 11/3 and a generalized amplitude factor instead of constant value 0.033. Therefore, in non-Kolmogorov weak turbulence, we carry out, for a uplink and a downlink paths, analysis of Long Term Beam Spread, Scintillation index, Proba...
We use the general non-Kolmogorov power spectrum for theoretical investigation of double-passage ... more We use the general non-Kolmogorov power spectrum for theoretical investigation of double-passage propagation of Gaussian beams in deep turbulence for the case of a point target. The presented results are of interest in LIDARs operating at high altitude, where non-Kolmogorov turbulence may be present.
Theoretical models and results of experimental campaigns relating to non-classic regimes occurrin... more Theoretical models and results of experimental campaigns relating to non-classic regimes occurring in atmospheric optical turbulence are overviewed. Non-classic turbulence may manifest itself through such phenomena as a varying power law of the refractive-index power spectrum, anisotropy, the presence of constant-temperature gradients and coherent structures. A brief historical introduction to the theories of optical turbulence, both classic and non-classic, is first presented. The effects of non-classic atmospheric turbulence on propagating light beams are then discussed, followed by the summary of results on measuring the non-classic turbulence, on its computer and in-lab simulations and its controlled synthesis. The general theory based on the extended Huygens–Fresnel method, capable of quantifying various effects of non-classic turbulence on propagating optical fields, including the increased light diffraction, beam profile deformations, etc., is then outlined. The review conclu...
Abstract. We use a non-Kolmogorov power spectrum for theoretical investigation of laser beam prop... more Abstract. We use a non-Kolmogorov power spectrum for theoretical investigation of laser beam propagation in the double-passage problem: transmitter–target–receiver. The major application of our work is the light detection and ranging (LIDAR) system operating in the zone of the atmosphere where non-Kolmogorov turbulence may be present. We show that the scintillation index is substantially affected by non-Kolmogorov turbulent channels at any turbulence strength. We consider the case of a small unresolved target and our analysis is valid for both the bistatic and monostatic configuration of the LIDAR system, in which the latter leads to the enhanced backscattering effects. Additionally, the paper contains a discussion of the simulation approach to light propagation through non-Kolmogorov turbulence. The simulation results and a discussion of their agreement with the theory are included. We found that the theory and the results of the simulations agree only to a certain extent. The “giant spikes” that occur when propagating through “deep turbulence” are responsible for the lack of better agreement. Their influence on the scintillation index and also on the probability density function of intensity probably requires a theoretical approach.
An experimental study has been performed of a laser beam propagating horizontally through the nea... more An experimental study has been performed of a laser beam propagating horizontally through the near-ground atmosphere above a grassy field at the University of Miami (UM) Coral Gables campus. The average intensity, scintillation index, and intensity correlation function are measured in the receiver plane for three channels with different turbulent conditions and at three different heights above the ground. Our results reveal that along short links (210 m) only the intensity correlation function captures the anisotropic information of turbulence, corresponding to the refractive index anisotropy ellipse of atmospheric fluctuations. In addition, we report an interesting phenomenon relating to turbulence eddy orientation near the ground. We confirmed that the experimental results are in agreement with the numerical simulations based on the multiple phase-screen method. Our findings provide an efficient method of determining the anisotropic parameters of atmospheric turbulence.
Atmospheric turbulence simulator is built and characterized for in-lab optical wave propagation w... more Atmospheric turbulence simulator is built and characterized for in-lab optical wave propagation with controlled strength of the refractive-index fluctuations. The temperature gradients are generated by a sequence of heat guns with controlled individual strengths. The temperature structure functions are measured in two directions transverse to propagation path with the help of a thermocouple array and used for evaluation of the corresponding refractive-index structure functions of optical turbulence.
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Papers by Italo Toselli