The proposed work addresses an opportunity to develop a portable, tunable backward wave oscillator (BWO) for room temperature generation of terahertz radiation. The approach combines microfabricated photonic crystal waveguide circuits with state-of-the-art electron guns to achieve the efficiency needed for portability. The initial devices will target the 1 to 2 THz range, though the approach can be applied to frequencies from 300 GHz to 3 THz