Page 329 - High Power Laser Handbook

298 So l i d - S t at e La s e r s Heat-Capacity Lasers 299

The physics of the digging phenomenon is as follows: because
of the HCL’s pulse format, the peak power generated in each laser
pulse is many times that of the laser’s average power. This high
peak power per pulse corresponds to a high peak temperature
increase in the soil substrate. All soils contain some residual amount
of moisture; the high peak power pulses of laser light generated by
the HCL impinge on the soil in a very focused area and vaporize the
moisture in the soil. This vaporization creates a microexplosion of
the moisture on a pulse-by-pulse basis. This microexplosion
generates the force required to displace the soil, allowing the laser
to penetrate to the intended target. Each laser pulse vaporizes more
moisture, thus creating more explosions, which allows the laser to
penetrate deeper and deeper into the soil. Once the laser hits the
outer casing of the mine, it rapidly begins to heat the material.
Within a few seconds, the temperature of the high explosive within
the mine is significantly raised (a few hundred degrees Celsius) to
initiate deflagration.
Figure 11.34 provides a concept drawing of the HCL system used
for humanitarian mine clearing. The system can be used for both bur-
ied and surface mines and can be operated at significant standoff dis-
tances to reduce the amount of human exposure within the blast-affected
zone. In addition, the HCL’s power can be easily modulated such that

Figure 11.34 Concept of the heat-capacity laser system used for
humanitarian mine clearing.