Widely tunable,high-power,femtosecond noncollinear optical parametric oscillator in the visible spectral range

Ultrafast visible radiation is of great importance for many applications ranging from spectroscopy to metrology.Because some regions in the visible range are not covered by laser gain media,optical parametric oscillators offer an added value.Besides a high-power broadband laser source,the ability to rapidly tune the frequency of pulses with high-power spectral density offers an extra benefit for experiments such as multicolor spectroscopy or imaging.Here,we demonstrate a broadband,high-power,rapidly tunable femtosecond noncollinear optical parametric oscillator with a signal tuning range of 440–720 nm in the visible range.The oscillator is pumped by the third harmonic of an Yb-fiber laser at 345 nm with a repetition rate of 50.2 MHz.Moreover,the signal wavelength is tuned by changing the cavity length only,and output powers up to 452 m W and pulse durations down to 268 fs are achieved.This is,to the best of our knowledge,the first demonstration of a quickly tunable femtosecond optical parametric oscillator that covers nearly the entire visible spectral range with high output power.

Simple route toward efficient frequency conversion for generation of fully coherent supercontinua in the mid-IR and UV range

Fiber supercontinua represent light sources of pivotal importance for a wide range of applications,ranging from optical communications to frequency metrology.Although spectra encompassing more than three octaves can be produced,the applicability of such spectra is strongly hampered due to coherence degradation during spectral broadening.Assuming pulse parameters at the cutting edge of currently available laser technology,we demonstrate the possibility of strongly coherent supercontinuum generation.In a fiber with two zero-dispersion wavelengths a higher-order soliton experiences a temporal breakdown,without any compression or splitting behavior,which leads to nearly complete conversion of input solitonic radiation into resonant nonsolitonic radiation in the dispersive wave regime.As the process is completely deterministic and shows little sensitivity to input noise,the resulting pulses appear to be compressible down to the sub-cycle level and may thus hold a new opportunity for direct generation of attosecond pulses in the visible to near ultraviolet wavelength range.

xtraction of internal phase motions in femtosecond soliton molecules using an orbital-angular-momentum-resolved method

Internal motions in femtosecond soliton molecules provide insight into universal collective dynamics in various nonlinear systems.Here we introduce an orbital-angular-momentum(OAM)-resolved method that maps the relative phase motion within a femtosecond soliton molecule into the rotational movement of the interferometric beam profile of two optical vortices.By this means,long-term relative phase evolutions of doublet and triplet soliton molecules generated in an all-polarization-maintaining mode-locked Er-fiber laser are revealed.This simple and practical OAM-resolved method represents a promising way to directly visualize the complex phase dynamics in a diversity of multisoliton structures.