A plasma lamp including a waveguide body comprising at least one dielectric material. The body is coupled to a microwave power source which causes the body to resonate in at least one resonant mode. A lamp chamber integrated with the body contains a bulb with a fill forming a light-emitting plasma when the chamber receives power from the resonating body. A bulb either is self-enclosed or an envelope sealed by a window or lens covering the chamber aperture. Embodiments disclosed include lamps having a drive probe and a feedback probe, and lamps having a drive probe, feedback probe and start probe, which minimize power reflected from the body back to the source.