Low noise femtosecond fiber laser mode-locked using a Single-Walled Carbon Nanotube-based saturable absorber

By replacing a semiconductor saturable absorber mirror (SESAM) made up of iron doped InGaAs/InP multiple quantum wells (MQW) (Gicquie-Guezo, 2004) by a saturable absorber incorporating nanotubes (SAINT) (Set, 2004) we have drastically decreased the noise level as well as improved the output pulse characteristics delivered by a passively mode-locked Er³⁺-doped fiber oscillator. Our laser consists of 235 cm-long, highly erbium-doped fiber core-pumped by a single-mode laser diode (120 mw max. power) and pieces of standard telecom fibers . A free space segment settles the cavity in order to manage beam focusing on the SA either constituted of SESAM or SAINT. The latter is made up of SW-CNT obtained by laser ablation of a doped graphitic target.

By replacing a SEmiconductor Saturable Absorber Mirror (SESAM) made up of Iron doped InGaAs/InP multiple quantum wells (MQW) [1] by a Saturable Absorber Incorporating NanoTubes (SAINT) [2] we have drastically decreased the noise level as well as improved the output pulse characteristics delivered by a passively mode-locked Er³⁺-doped fiber oscillator. Our laser consists of 235 cm-long, highly erbium-doped fiber core-pumped by a singlemode laser diode (120 mw max. power) and pieces of standard telecom fibers as shown in Fig 1a. A free space segment settles the cavity in order to manage beam focusing on the SA either constituted of SESAM or SAINT. The latter is made up of SW-CNT obtained by laser ablation of a doped graphitic target. Then purification is made by an acid and ultrasonic treatment before to be rinsed out with hydro-genperoxyde, filtered and dispersed through ultrasonic agitation in N-Methyl-Pyrrolidone. Finally, the suspension is deposited directly on a gold mirror by spin-coating. Various deposition have been performed and analyzed by STM microscopy and their influence on mode-locking will be discussed. Figure 1a Experimental set-up. MUX: 980/1550 nm multiplexer; Fig. 1b: A typical self-starting mode-lock regime MO: AR coated microscope objectives (X20-N.A: 0.35) Figure 1b A typical self-starting mode-lock regime follows an oscillatory transient Q-switch one