This SBIR phase I project proposes a single frequency high energy resonant amplifier for remote sensing. Current state-of-art technologies can not provide all features of high energy and efficiency, compactness, and narrow spectral width. PolarOnyx proposes, for the first time, a high energy (100 mJ) resonant amplifier to meet with the requirement of solicitation. This proposal is based on the spectral shaping sub-mJ fiber laser at 1550 nm we have achieved in our labs. In the high power amplifier stage, PolarOnyx proposes an innovative resonant cavity based amplifier approach by employing our patent pending proprietary technologies in hybrid high energy amplifiers, that will be able to operate at low repetition rate (10's Hz to 1 kHz) and reach high energy level of 100 mJ. These will make the hybrid fiber laser transmitter system superior in terms of wall plug efficiency (over 30%), energy(100 mJ), noise, size, and cost. A tabletop experiment will be demonstrated in Phase I time frame for proof of concept. A compact prototype will be delivered in Phase II.