The cw pumped orange (620-nm) colliding pulse mode-locked (CPM) dye laser1 has for several years routinely produced the shortest and most stable femtosecond laser pulses. Unfortunately, the optimum conditions for short pulse generation always preclude tunability because of the critical balance of saturable absorption and saturable gain,2 which is obtained very nicely with a rhodamine 6G gain dye and a DODCI saturable absorber at around 625 nm. The extension of this technique to any new wavelengths represents a major project in every case, since many parameters have to be optimized to obtain proper low noise CPM operation. A number of conditions have been investigated.3 However, the rhodamine 6G DODCI dye combination is still by far the most common pair for CPM operation in actual applications.
© 1990 Optical Society of AmericaPDF Article