Nanosecond-pulse fiber lasers mode-locked with nanotubes

Abstract

We demonstrate that mode-locking of ytterbium fiber lasers with a carbon nanotube saturable absorber can produce pulses ranging from 20 ps to 2 ns at repetition rates between 21 MHz and 177 kHz, respectively, depending on cavity length. Nonlinear polarization evolution is not responsible for mode-locking. Even in the nanosecond regime, clean single pulses are observed and the pulse train exhibits low jitter. Combined with extremely large chirp, these properties are suited for chirped-pulse amplification systems.

Carbon nanotubes for ultrafast fibre lasers

“…The normal dispersion laser cavity provided generation of 1.5-ps chirped pulses, which could be compressed down to 250 fs outside the cavity [50]. In Kelleher et al [223], the possibility of pulse duration adjustment was demonstrated within the range from 20 ps to 2 ns at repetition rates between 21 MHz and 177 kHz. Mode-locked operation in Yb-doped fibre lasers was also demonstrated using DWNT-SA [72].…”

Mode-locking in 25-km fibre laser

“…The next level was achieved in the breakthrough works [5,6] in mode-lock fibre lasers with a several km cavities. Other examples of passive mode locking in fibre lasers with > 1 km resonators have been demonstrated in the subsequent works [7][8][9][10][11][12]. Such a dramatic elongation of the laser resonator led to more than two orders of magnitude increase in the output pulse energy at the same pump power.…”

Ultrafast Raman laser mode-locked by nanotubes

“…Mode-locked lasers based on rare-earth media and operating with a net normal dispersion map, generating so-called dissipative solitons [12,16,17], were suggested as a means of overcoming the limits on pulse energy imposed by the soliton regime. Such systems were shown to support highly linearly chirped pulses [12,16,17], with durations up to several nanoseconds [12]. Thus they can be amplified and compressed without temporal and spectral degradation due to nonlinearities.…”

“…The square-shaped spectrum is a recognizable feature of lasers operating in the dissipative soliton regime [12]. Such systems generate pulses carrying a large and predominantly linear chirp [12], and are suitable for compression [12]. The RF trace [ Fig.…”

“…Availability of a broadband saturable absorber (SA) to achieve mode-locking at any desired wavelength across the transmission window of silica is an essential prerequisite to fully exploit the flexibility of Raman amplification in ultrafast sources across the visible and near-IR. Recent interest in the application of nano materials, in particular carbon nanotubes (CNTs) [9][10][11][12] and graphene [10,[13][14][15], as SAs in mode-locked lasers have moved the field a step closer to a fully universal device [9][10][11][12][13][14][15]. For example, a single CNT-based SA was used to mode-lock fiber lasers, offering wide wavelength-tunable pulses [11] and broad spectral coverage from 1 to 2 μm [9].…”