Environmental CW range-resolved S-lidars with Si/InGaAs arrays: limitations and capabilities under sky background.

In this paper, we discuss some features of open-path remote sensing inherent to CW range-resolved S-lidars (S comes from Scheimpflug) as a new, to the best of our knowledge, and promising class of laser instruments for environmental monitoring. In many remote-sensing applications, the accompanying skylight can degrade the sensitivity and overload the photodetectors, which is also very relevant for S-lidars with Si and InGaAs arrays. We paid special attention to the topical problem of predicting the limitations and potential of S-lidars in the VIS and SWIR spectral bands, where the sky background is particularly strongly affected. For this purpose, the index of immunity against external backgrounds as a quantitative indicator of S-lidars' potential insensitivity to the current skylight is introduced. Its evaluation is carried out by comparing the potentially achievable signal-to-noise ratios at the detector output in the presence and absence of external illumination. The detector response to the skylight in the photon-counting mode is normalized to appropriate parameters of the array in order to use dimensionless estimates in describing the variability of conditions. Characteristic spectral and dark-current-related features distinguishing the response of Si and InGaAs array detectors in the presence of background illumination are taken into account. It is then shown how to determine the minimum required full well capacity of the array in order to neglect the skylight contribution and ensure stable operation of S-lidars. The proposed methodology is aimed at providing a rationale for design solutions to expand the applicability of this promising type of remote sensors.

Modeling of microjoule and millijoule energy LIDARs with PMT/SiPM/APD detectors: a sensitivity analysis.

This paper demonstrates a renewed concept and applications of the generalized methodology for atmospheric light detection and ranging (LIDAR) capability prediction as a continuation of a series of our previous works, where the dimensionless parameterization appeared as a tool for comparing systems of a different scale, design, and applications. The modernized concept applied to microscale and milliscale LIDARs with relatively new silicon photomultiplier detectors and traditional photomultiplier tube and avalanche photodiode detectors allowed prediction of the remote sensing instruments' performance and limitations. Such a generalized, uniform, and objective concept is applied for evaluation of the increasingly popular class of limited-energy LIDARs using the best optical detectors, operating on different targets (back-scatter or topographic, static or dynamic) and under intense sky background conditions. It can be used in the LIDAR community to compare different instruments and select the most suitable and effective ones for specific applications.

Dimensionless parameterization of lidar for laser remote sensing of the atmosphere and its application to systems with SiPM and PMT detectors.

In this paper, we show a renewed approach to the generalized methodology for atmospheric lidar assessment, which uses the dimensionless parameterization as a core component. It is based on a series of our previous works where the problem of universal parameterization over many lidar technologies were described and analyzed from different points of view. The modernized dimensionless parameterization concept applied to relatively new silicon photomultiplier detectors (SiPMs) and traditional photomultiplier (PMT) detectors for remote-sensing instruments allowed predicting the lidar receiver performance with sky background available. The renewed approach can be widely used to evaluate a broad range of lidar system capabilities for a variety of lidar remote-sensing applications as well as to serve as a basis for selection of appropriate lidar system parameters for a specific application. Such a modernized methodology provides a generalized, uniform, and objective approach for evaluation of a broad range of lidar types and systems (aerosol, Raman, DIAL) operating on different targets (backscatter or topographic) and under intense sky background conditions. It can be used within the lidar community to compare different lidar instruments.

Intensity-modulated linear-frequency-modulated continuous-wave lidar for distributed media: fundamentals of technique.

We analyze the intensity-modulation frequency-modulated continuous-wave (FMCW) technique for lidar remote sensing in the context of its application to distributed media. The goal of the technique is the reproduction of the sounded-medium profile along the emission path. A conceptual analysis is carried out to show the problems the basic version of the method presents for this application. The principal point is the appearance of a bandpass filtering effect, which seems to hinder its use in this context. A modified version of the technique is proposed to overcome this problem. A number of computer simulations confirm the ability of the modified FMCW technique to sound distributed media.

Spatial filtering efficiency of monostatic biaxial lidar: analysis and applications.

Results of lidar modeling based on spatial-angular filtering efficiency criteria are presented. Their analysis shows that the low spatial-angular filtering efficiency of traditional visible and near-infrared systems is an important cause of low signal/background-radiation ratio (SBR) at the photodetector input The low SBR may be responsible for considerable measurement errors and ensuing the low accuracy of the retrieval of atmospheric optical parameters. As shown, the most effective protection against sky background radiation for groundbased biaxial lidars is the modifying of their angular field according to a spatial-angular filtering efficiency criterion. Some effective approaches to achieve a high filtering efficiency for the receiving system optimization are discussed.