An electrodeless plasma lamp apparatus includes a waveguide body having at least a first material and a second material. At least one of the materials has a dielectric constant of less than two. In a specific embodiment, the apparatus also includes an RF power source coupled to the waveguide body to provide RF power to the waveguide body at least one frequency that resonates within the waveguide body. A bulb containing a fill which forms a plasma to cause emission of light when the RF power is provided to the waveguide body.