Light bridge

"“I’m showing a lot of photonic activity,” Cortana said. “The excited photons have displaced the air around the light path.” “Which means?” “Which means,” she continued, “that the light has become coherent. Solid.”"

- Exchange between the Master Chief and Cortana

Energy Bridges, also known as Light Bridges, are examples of advanced Forerunner technology.

Summary
There are usually two components to an Energy bridge: a control panel, and the light emitters. The control panel is a semi-translucent holographic array of Forerunner symbols and glyphs that are projected over the surface of a pedestal. Tapping the "blue-green circle" activates the light emitters. The photons become excited, and are stimulated by unknown means to "displace the air around them", becoming a firm, solid mass capable of supporting extremely heavy weights, ranging from a M12 Warthog LRV to several M808B Scorpion MBT's. When damaged, the emitters flicker on and off, causing the light bridge to flicker, creating a less stable force.

Energy Bridges were present in Halo: Combat Evolved, they are used by the Master Chief during the UNSC's operations on the surface of Installation 04, in the subterranean complexes and the Flood Containment Facilities.

Though mainly unseen on Installation 05, they are also present on the Ark, again in a subterranean area, and another two close to the Citadel near the Ark's Core.

Real-World Theories
Solid Light is a theory that says light can behave as a solid. Andrew Greentree, Jared Cole, and Lloyd Hollenberg of the University of Melbourne and Charles Tahan of the University of Cambridge demonstrated theoretically how to engineer a phase transition in photons, leading them to change their state so that they do interact with each other. According to them this technology will help build new kinds of faster computers. The Energy Bridge makes for produced energy to jut out of a given complex; this exerts a lot of focus in Universities on the matter.

Trivia

 * There are four locations known for an energy bridge. The first and second are the bridges on the level Halo, and the bridges on the level 343 Guilty Spark from Halo: Combat Evolved, the third being the one on the Ark on the level The Ark in Halo 3, and the last being the one in the Citadel on The Covenant.