Various devices for delivering light and/or ultrasound to the skin of a patient for therapeutic or cosmetic purposes are known in the art. In general, these devices do not provide uniform light and/or a uniform ultrasound field across the surface of the device. For example, when conventional light emitting diodes (LEDs) are used as a light source, each LED operates as a point source that can generate a hot spot if positioned too close to the patient's skin. Also, because typical LEDs have a relatively large beam divergence (e.g., about 65 degrees on each side for a total of 130 degrees), the light field is not uniform unless the LEDs are positioned a sufficient distance from the tissue. As another example, many conventional ultrasonic transducers have a beam non-uniformity ratio (i.e., the ratio between peak intensity and average intensity in the beam) of 5 to 6 or higher. As a result, the intensity of the ultrasound varies across the surface of the device.