Airborne Laser Illuminator Delivered

Brent D. Johnson

The US Department of Defense's Missile Defense Agency has made some strides in developing optical technology for antimissile systems. The latest achievement is Northrop Grumman Corp.'s beacon illuminator laser, which is part of the beam control/fire control system for the Airborne Laser, a jet-based high-power system that, the developers hope, will be able to destroy incoming missiles in their boost phase.

Northrop Grumman Corp. has delivered the high-power solid-state beacon illuminator laser for the Airborne Laser's beam control/fire control system. It will be used to determine the wavefront error caused by atmospheric turbulence between the system's megawatt-class chemical laser and the target.

Wavefront error

In application, the beacon illuminator laser will emit radiation to determine the wavefront error caused by turbulence in the atmosphere between the system and the target. The signal reflected from the target will pass through a series of wavefront sensors. The sensors will direct deformable mirrors to compensate for optical distortion by manipulating the phase conjugation on the chemical oxygen iodine laser, focusing the "killer" beam on target.

The illumination beam initiates in the master oscillator, which is a diode-pumped Nd:YAG slab laser. Each of the two line-replaceable units features an oscillator, producing a 1064-nm pulse that is injected into three amplifiers.

After amplification, the illumination beam is focused into a stimulated Brillouin scattering cell, which uses sound waves to correct for induced aberration. Although the power of the system is rated as kilowatt-class, the final power and beam quality are classified.

Adapting the laser from a lab breadboard to satisfy the requirements of small size and low weight --necessary for deployment on an airborne platform for the military -- while protecting the optics from stray light and vibration loading required a great deal of thought and effort, said Steven Hixson of Northrop Grumman Space Technology in Hawthorne, Calif. But the company's experience with chemical lasers eased the development of the optics, packaging, cooling and alignment technologies.
The beacon illuminator laser has been delivered to Lockheed Martin's test facility in Sunnyvale, Calif., where it will undergo testing before it is mounted in a Boeing 747-400 freighter aircraft.