Figure 1.

(a) Laser setup. Inset: the assembly of SWNT saturable absorber. EDF, erbium-doped fiber; WDM, wavelength-division multiplexer; PC, polarization controller; LD, laser diode; CIR, circulator; CFBG, chirped fiber Bragg grating; SWNT, single wall carbon nanotube. (b) Reflection spectra of three CFBG_1–3. (c) Nonlinear absorption characterization of the SWNT saturable absorber. The solid curve is fitted from the experimental data (circle symbols). (d) Absorption spectrum of the SWNT–polycarbonate composite and pure polycarbonate. The red stripe illustrates the spectral gain region of the Er³⁺-doped fiber.