Multi-pixel short-wave infra-red (SWIR) Geiger-mode avalanche photodiode (GmAPD) light detection and ranging (LIDAR) sensors have enabled unprecedented 3D imaging capabilities in commercial and government platforms. Traditionally, GmAPD sensors operate in range-gated synchronous mode and direct-detect (DD) single photons transmitted by the laser light that is back scattered from distant object. In this work, we explore performance metrics of asynchronous GmAPD sensors for single photon direct-detect as well as coherent-detect (CD) systems. The characteristics of free-running pixels, photon detection efficiency (PDE), dark-count rate (DCR), as well as bandwidth and jitter are discussed specific to DD and CD single-photon sensor operation.

Best practices for the verification and validation of 3D absolute and predicted accuracy of LIDAR data utilizes both point and area ground control surveys. A comparison of both approaches indicates that the legacy (DGPS point survey) provides a rigid, well defined estimate of the measured total accuracy that can be directly compared with predicted accuracy models using the Generic Point-cloud Model (GPM 1.1) construct for modeling sensor measurement error. In contrast, the area ground control approach, often using terrestrial or drone based LIDAR sensors can provide a much higher density survey of the test site, but with a fundamentally different perspective on the absolute accuracy of the site under measurement and consequently the predicted accuracy of the survey. Comparisons of both approaches highlight the strengths and weaknesses of both approaches, especially in the characterization of non-traditional features including building corners, building centers, and building sides.

Transparent electro-optic (EO) devices can potentially be used for efficient, high speed, and low mass non-mechanical beam steering. Transmission through EO devices will affect the wavefront quality and aberration of both the transmitted and received laser light. The consequences of wavefront distortions on coherent detection are not fully understood. Therefore, we have tested the performance of coherent detection lidar using liquid crystal polarization grating (LCPG) beam steering device. We will discuss the impact of LCPG beam steering devices on the performance of NASA’s Navigation Doppler Lidar, built for providing altitude and vector velocity data to aerial and space vehicles.

This conference presentation was prepared for SPIE Defense + Commercial Sensing, 2023.

A compact, high energy and high repetition rate microchip laser platform with tailorable parameters for a wide range of novel sensing applications is presented. The source provides tunable pulse repetition rates from 1 - 200 kHz. The pulse duration can be tailored to cover 100 ps to nanosecond-range at 1064 nm, and sub-ns to several ns at 1535 nm. The highest pulse energy directly from the compact seed laser is 12 µJ, for 1 kHz operation and 1535 nm, making it very attractive for long-range eye-safe sensing applications. The 1064 nm, 100 ps laser source can provide up to 2 kW of peak power at 150 kHz making it attractive for high-resolution LIDAR applications. The microchip architecture allows for an extremely compact footprint enabling high durability and operation in extreme environmental conditions.