An electroluminescent blade, often called EL blade for short, is a lightsaber blade type utilizing a electroluminescent (EL) sheet or wire that runs the length of the blade. The EL sheet or wire is housed in a diffuser tube inside a polycarbonate blade tube. The EL sheet or wire illuminates the lightsaber blade. An EL blade is used with an EL lightsaber hilt.
The two earliest Master Replicas Force FX Lightsabers, the 2002 Anakin Skywalker (AOTC) Force FX lightsaber and the 2003 Luke Skywalker (ROTJ) Force FX, use EL blades. Subsequent Master Replicas Force FX lightsabers use LED string blades instead. Custom saber company Parks Sabers offered a line of EL Sabers from 2000 to 2009.
EL blades and EL lightsabers are no longer commonly produced. Most lightsaber companies and makers now favor alternative, often brighter illumination technologies/methods like LED string blades, in-hilt LEDs, or the ultra-bright neopixel blades.
COVER IMAGE CREDIT Parks Sabers (via archive.org)
Cover image depicts various EL Sabers from Parks Sabers