A novel compact air-cavity electrodeless high intensity discharge lamp is disclosed that provides added flexibility in its design to improve performance and reliability. A coupling sleeve surrounds a bulb assembly that can replace the output coupling element require for effective operation of the lamp. The coupling sleeve couples the RF energy from the input coupling element to the bulb and the bulb assembly serves to provide the heat sinking needed for the bulb to operate within the temperature range necessary to achieve optimum performance with good reliability. Changing the design of the bulb assembly does not impact the resonant frequency of the air-cavity resonator. De-coupling the bulb assembly design from the operating frequency of the resonator gives more flexibility to designer to optimize the overall performance of the electrodeless HID lamp.