Mode-locked He-Ne laser pulse compression and expansion

By means of an electro-optic internal modulator it is possible to obtain from a laser He-Ne recurring pulses whose duration (about 500 psec) is the inverse of the Ne amplifying spectral bandwidth. The optical frequency of these pulses, passing through an external modulator is translated or linearly modulated. The duration of the linear frequency modulated pulses, whose spectrum is widely broadened, is then reduced by travels into a dispersive interferometric structure (optical dispersive delay line). A pulse compression ratio at least equal to 3 has been obtained.