Toward single-cycle laser systems

摘要

Few-cycle pulse generation based on Ti:sapphire, Cr:forsterite, and Cr:YAG gain media is reviewed. The dynamics of these laser systems is well understood in terms of soliton and dispersion managed soliton formation stabilized by artificial saturable absorber action provided by Kerr-lens modelocking. These systems generate 5-, 14-, and 20-fs pulses with spectral coverages of 600-1150, 1100-1600, and 1200-1500 nm, respectively. The design of dispersion compensating laser optics providing high reflectivity and prismless operation over this bandwidth is discussed. A novel active synchronization scheme based on balanced optical cross correlation, the equivalent to balanced microwave detection, for synchronization of independently mode-locked lasers is introduced. Its use in synchronizing an octave-spanning Ti:sapphire laser and a 30-fs Cr:forsterite laser yields 300 attoseconds timing jitter measured from 10 mHz to 2.3 MHz. The spectral overlap between the two lasers is large enough to enable direct detection of the difference in the carrier-envelope offset frequency between the two lasers. These are the most important steps in the synthesis of single-cycle optical pulses with spectra spanning 600-1600 nm.