Low-temperature synthesis of a carbon nanocage saturable absorber for pulsed erbium-doped fiber laser generation

Exploring a new photonic material with low preparation cost, good optical stability and nonlinearity at the near-infrared waveband is important for ultrafast optical science and devices. Here, with a relatively low carbonization temperature (350, 400, and 450 degrees C), carbon nanocages (CNCs) are synthesized by pyrolyzing ethylenediamine trapped inside the zeolite ZnAlPO-12 template. It is found that the nonlinear saturable absorption properties of the as-synthesized CNCs are highly dependent on the fabrication temperature. The modulation depth of the CNCs can be decreased from 45% to 35.2% by increasing the fabrication temperature from 350 degrees C to 450 degrees C. By incorporating the CNC-based SAs that were fabricated under different temperatures into an erbium-doped fiber laser cavity, either Q-switching or mode-locking with high operational stability can be obtained in the same fiber laser cavity. To the best of our knowledge, this is the first demonstration of a CNC-based SA to achieve a pulsed fiber laser, which proves the excellent nonlinear optical properties of the CNCs and lays a foundation for their development in photonic devices.