OPTICAL SHUTTER FOR ACTIVE RANGE-GATED ELECTRO-OPTIC IMAGING

TP Engineering personnel have extensive experience with electro-optic systems and high Pulse Repetition Frequency (PRF) Laser systems. We have detailed knowledge of Pockels cell systems enabling active gated imaging through foliage at PRF <30 Hz. Recent improvements in electro-optic materials, optical devices and high voltage driver technology enable extension of these early devices to >100 kHz PRF. Such systems can dramatically improve and protect Geiger-mode LIDAR by both controlling the transmitter output and gating out unwanted return light from atmospheric backscatter, foliage or even other laser sources (adversarial or inadvertent). We have developed two competing designs for NGA212-001. The first design utilizes KTP, exhibits low half-wave voltage, high transmission, high laser damage threshold and can be operated to repetition rates over 500 kHz. While this design is ideal for laser pulse picking, it has difficulty achieving the wide-angular field required for imaging. The second utilizes a unique, custom longitudinal field design that offers very wide-angle capability and repetition rate to >100 kHz with 90% transmission. While this design is ideal for range-gated imaging, the laser damage threshold must be evaluated for laser pulse picking. Both designs utilize birefringent compensation to improve the off-axis performance. Our Phase I effort will use extensive modeling and simulation to predict the performance of each design for gated imaging, countermeasure protection and laser pulse picking (NGA-212 requirements) as a function of repetition rate, voltage and ray angle (off-axis). This model will be validated by building a rapid prototype of one of the cells in Phase I and comparing the performance to model calculations. The objective is to mature the design to sufficient detail that a Preliminary Design can be completed early in Phase II to enable the build of two prototypes in Phase II. By executing a build, test, build strategy, the unit delivered in Phase II (Breadboard #2) can employ the lessons learned from Breadboard #1.