SBIR-STTR Award

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.

In Phase I we developed and demonstrated a bi-directional, monolithic, High-Speed, Electro-optic shutter for Range Gated Imaging. While meeting the majority of the key performance parameters for Range-Gated Imaging at high Pulse Repetition Frequency, improvements can be achieved in transmission, contrast and reliability. The Phase Ii activity begins with a upgraded Electro-optic Shutter incorporating the lessons learned from Phase I testing. Following demonstration of these improvements, a second engineering cycle will produce a EO shutter designed for the temperature range, pressure and ruggedization necessary for high-altitude flight. In parallel to development of the flight-prototype Electro-optic cell, we will develop the Electric Power and Switching System (EPSS). The EPSS produces the nanosecond pulses at high-voltage and high Pulse Repetition Frequency necessary to drive the EO cell. Together, the EO cell and EPSS provide a complete Electro-optic shutter assembly meeting the performance and environmental requirements of NGA-212-001 for range-gated imaging. Two Flight Prototype Range-Gate (FPRG) units will be provided. In parallel to the development of the Flight Prototype Range-Gate EO shutter assemblies, we will develop the Focal Plane Array Shutter (FPAS). The FPAS builds on the Phase I EO Cell to meet the countermeasure objective of NGA-212. Specifically, the objective here iOS to develop a broadband electro-optic shutter capable of providing a variable transmission capability to protect Electrooptic Focal Plane Arrays and sensors from blinding or destruction by incident laser light. Our Phase I cell demonstrated the most difficult objective (bandwidth) and placed us in position to engineer the FPAS unit during Phase II. A full FPAS consisting of the EO Cell and Electric Power and Switching System (FPAS-EPSS) will be developed and testing int he laboratory. The FPAS shall detect incident laser light and rapidly close the shutter to protect the downstream focal plane array. Finally, we intend to develop the third device sought in NGA-212-001, the Laser Pulse Picker (LPP). The laser pulse picker exhibits requirements radically different in terms of angular acceptance, laser damage threshold, etc from the Electro-optic shutters for range-gated imaging and/or EO sensor protection. As a result, we will develop a fast Electro-optic cell for this specific purpose. We will complete the Critical Design of the Laser Pulse Picker. If sufficient funds and schedule remain after completion of the FPRG and FPAS, we will build and test the LPP in the laboratory during Phase Ii.