View Full Version : Femtosecond lasers fool heat-seeking missiles

Dr Mordrid
10th June 2006, 22:41

A femtosecond laser's ability to generate an intense electric field makes it ideal for disrupting missiles that use infrared guidance systems. Emmanuel Marquis describes a ground-based solution that could protect civilian and military aircraft against missile attacks.

Femtosecond lasers emit pulses that reach tremendously high peak powers and moderate energies. Such ultrafast pulsed lasers exhibit a very interesting effect: even at low energy operation, the electric field generated at the focal spot of the beam reaches high levels. For example, 100 mJ, 100 fs pulses generate a peak power of 1 TW and an electric field in excess of hundreds of megavolts in the focal spot.
Our airport protection concept relies on truck-mounted lasers that are deployed on the extremities of each runway to safeguard departing and arriving aircraft. Each truck is equipped with a femtosecond laser and a rotary turret to cover the appropriate angular sector.

For example, the laser would be a chirped-pulse amplification system based on a Ti:sapphire lasing media, with a repetition rate of 10 or 100 Hz. Several terawatts of peak power at 800 nm are required for efficient long filament production in the air and the laser has to be equipped with a spectral phase-shaper to provide air propagation dispersion compensation.

Such laser jammers can be spread every 5-10 km on the ground to protect a complete access corridor and as they are truck-mounted, reconfiguration of the protected airspace is quite easy.

The system has two modes of operation. In preventive mode, the laser is permanently firing and protects a pre-determined zone in the airspace. A simple example would be to create a plasma shield below the aircraft's flight path. There is also the option to change the trajectory of the plasma and divert the missile.

In defensive mode, the laser is on standby and is triggered by a missile launch detector. Such an alert would also give the coordinates of the launch point allowing the laser to be fired into the missile's estimated trajectory. The missile launch detector is either a classical rocket plume optical detector or a microwave Doppler radar system that leads to a much better false alarm rate.http://www.cnn.com/2006/AUTOS/06/07/pluggedin_fortune/index.html

Dr. Mordrid