DID YOU KNOW? DTIC has over 3.5 million final reports on DoD funded research, development, test, and evaluation activities available to our registered users. Click HERE
to register or log in.
THz Photonics in Water and Beyond
In the THz frequency range, laser-induced air plasma has become one of the most popular THz sources in the research laboratories. It can generate THz waves with a field strength of over MV/cm level by two-color optical excitation. The transient field is strong enough to induce nonlinearity. Recently, THz wave generation from ionized liquids, especially from liquid water, has also been successfully demonstrated. Liquids are preferable to general targets, as a flowing liquid line provides a fresh area for each excitation pulse, so the chaos caused by the previous pulse will not influence the next one. This makes it possible to use a high repetition rate laser for excitation. THz wave generation from ionized liquids presents photoionization processes that are different from those in gases. The most important difference is the preference of liquid for excitation with a sub-picosecond pulse. In gas, the shortest pulse always generates strongest THz field, but in liquids, in a big surprise we have found that a laser pulse with longer pulse duration offers stronger THz emission!
Approved For Public Release