Modelocking of a Wavelength Tunable High-Pressure CO₂-Laser by Synchronous Modulation of a Broadband Intracavity Saturable Absorber

Abstract

In recent years, both passive and injection modelocking has been applied to the multiatmospheric CO₂-laser for generation of subnanosecond pulses of high power radiation at the 10.6 pm wavelength, thus taking advantage of the strongly pressure broadened bandwidth (1,2). On the other hand, continuous wavelength tuning over significant range from 9 to 11 μm of the freerunning laser can be readily obtained by operating the laser in the 10 atm pressure range. In spite of the many potential and attractive applications, for example to time-resolved spectroscopy of molecules, there appears to be no reported success of short pulse generation with such wavelength tunability. We have combined in a simple scheme elements of both forced and passive modelocking to provide a versatile source with good tuning characteristics. The difficulties with reliability in modelocking which are generally connected with the relatively high gain and its short lifetime in high pressure lasers were here reduced by additional external optical modulation of absorption losses in intracavity p-Ge.