Objective During propagation through turbulent atmospheric environments, laser beams experience phenomena such as scintillation, drift, and angle-of-arrival fluctuations due to random refractive index variations. These effects severely degrade beam quality and stability, which impacts applications such as laser communication, synthetic aperture lidar, and other optoelectronic systems. Atmospheric turbulence is spatially and temporally variable, making controlled experimental studies challenging. Laboratory-based turbulence simulators, capable of generating reproducible and controllable turbulence, offer a practical solution. However, existing measurement systems for such turbulence simulators lack the ability to simultaneously achieve high precision, high-frequency sampling, and multi-parameter synchronization, limiting the detailed characterization of turbulence properties. This study aims to develop a dedicated measurement system for turbulence simulators and conduct comprehensive analyses of turbulence characteristics under varying conditions, providing critical data for turbulence simulator performance evaluation and turbulence propagation studies.

Methods A specialized measurement system (Fig.1) was designed to synchronously capture turbulence parameters including angle-of-arrival fluctuations, laser beam wander, scintillation index, and coherence length. The system integrates position-sensitive detectors (PSD) for laser centroid displacement and photomultiplier tubes (PMT) for intensity fluctuations, from which the power spectra of the angle-of-arrival, beam wander, and scintillation can be obtained. The coherence length is measured by the differential image motion method (DIMM), and the performance of the system in measuring the coherence length was analyzed according to the national standard. This system was used in a hot-air convection turbulence simulator (Fig.2). Turbulence intensity and spectral characteristics were analyzed by varying the temperature difference between the plates and the transverse wind speed.

Results and Discussions The coherence length measurement demonstrated an uncertainty better than 5% within a 245 cm dynamic range, outperforming conventional systems (10% uncertainty in 2-30 cm). This system was used in a hot-air convection turbulence simulator. In convection turbulence mode, coherence length exhibited a logarithmic-linear relationship with plate temperature differences (Fig.3), spanning from weak turbulence to conditions exceeding natural atmospheric turbulence by an order of magnitude. Longitudinal beam wander drift variance exceeded transverse wander by an order of magnitude (2.42-984 μrad² vs. 27.7-7210 μrad²). (Tab.3) Angle-of-arrival and beam wander power spectrum (Fig.4, Fig.6) showed high similarity, with transverse wind significantly increasing cutoff frequencies (from approximately100 Hz to 600 Hz). In convection turbulence mode, high-band fitting power rate fluctuated near −11/3, shifted to −8/3 under forced hot-air turbulence mode Fig.5, Fig.7). PMT measured scintillation power spectrum exhibited broader bandwidths due to reduced aperture averaging, necessitating higher sampling rates (>1000 Hz) for full spectral resolution (Fig.8).

Conclusions In view of the shortcomings of the current turbulence measurement methods in the turbulence simulator, a set of high precision and high sampling frequency multi-parameter synchronous measurement system was designed and developed, which was successfully applied to the turbulence measurement in the new hot air convection turbulence simulator, and the test results under different environmental conditions were obtained. In pure convection mode, the turbulence intensity increased with the temperature difference between the plates, exhibiting a logarithmic-linear relationship across the entire achievable temperature range of the simulator. Simultaneously, the variance of the beam wander drift was greater in the longitudinal direction than in the transverse direction, attributable to the longitudinal convection design of the simulator, which induces stronger airflow dynamics along its longitudinal axis. After full turbulence development, the angle-of-arrival fluctuation spectrum and the beam wander drift spectrum exhibited similar characteristics in their cut-off frequency and high-frequency power-law slope. When the simulator was switched from pure convection to hot-air mode (using fans), the cut-off frequency increased significantly, and the high-frequency power-law slope steepened, shifting from approximately −11/3 to around −8/3. Due to reduced aperture averaging effects, the scintillation spectrum measured by a small-aperture PMT exhibited a broader power spectrum. Capturing the complete spectral shape therefore requires a measurement device with a higher acquisition bandwidth.