We report on a single-pass device that efficiently converts the broadband near-infrared output from a femtosecond fiber laser into a narrow spectrum in the visible. With fan-out poled MgO:LiNbO3 we obtain sub-picosecond, continuously tunable pulses in the 520-700 nm range. Conversion efficiencies as high as 30% are observed at typical pump power levels of 30 mW, corresponding to average output powers up to 9.5 mW. The specifications of our device are ideal for applications in confocal microscopy and frequency metrology.
We present what is believed to be the first direct measurement of the relative timing jitter between the two parallel pulse trains of a two-branch femtosecond erbium-doped fiber laser, operated without active stabilization. The system provides independently tunable pulses in the near infrared with durations down to 13 fs. Using an interferometric optical cross-correlator, the phase-noise spectral density is measured with high sensitivity in a range from 1 Hz up to the Nyquist frequency of 24.5 MHz. We find an integrated jitter of 11 attoseconds directly after the amplifier stages and 43 as after propagation through free-space optics and nonlinear fibers for frequency conversion.
We report on highly efficient second, third and fourth harmonic generation from a femtosecond erbium-doped fiber source operating at 98 MHz repetition rate. By use of quasi-phase-matching in fan-out poled MgO:LiNbO(3), we generate pulses at 770 nm, 520 nm and 390 nm, with corresponding average powers of 120 mW, 55 mW and 6 mW, respectively. Our device can be employed as a two-color source providing radiation from ultraviolet to near infrared.
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