Non-thermal Micro Adjustment Using Ultrashort Laser Pulses

In the field of micro technology highest accuracies have to be attained regarding position, angles and distances.To achieve this task within reasonable expenses roughly tolerated assembly followed by high-precision adjustment is often applied.As the final tolerances tend to get smaller in the same manner as the dimension of the devices common adjustment processes are reaching limits rapidly.To provide a better solution for this discrepancy the Bavarian Laser Centre investigates a new process of highly accurate, contact-free and time-efficient micro adjustment for a wide variety of materials using ultrashort laser pulses.The process mechanism is based on the effect that an ultrashort laser pulse of high intensity is able to produce plasma on the surface of the absorbing bulk material in nearly isochoric manner.The following expansion of the plasma into the confining medium excites shock waves propagating into the bulk material due to recoil effects.These shock waves, which rapidly decay to compressional waves, induce near-surface plastic deformation which results in bending the actuator's free end away from the laser beam.With suitable actuators this can be used for highly accurate adjustment.Results of previous investigations show that the bending angle can achieve accuracies in the scale of a few 10 µrad while allowing maximum deflections of a few degrees.Up to now copper, steel, silicon and pyrex-glass have been successfully deformed with this process.