Fibre lasers in the mid-infrared regime are useful for a diverse range of fields, including chemical and biomedical sensing, military applications and materials processing. This Review summarizes the different rare-earth cations and host materials used in mid-infrared fibre laser technology, and discusses the future applications and challenges for the field.

Towards high-power mid-infrared emission from a fibre laser

Polymer composites are one of the most attractive near-term means to exploit the unique properties of carbon nanotubes and graphene. This is particularly true for composites aimed at electronics and photonics, where a number of promising applications have already been demonstrated. One such example is nanotube-based saturable absorbers. These can be used as all-optical switches, optical amplifier noise suppressors, or mode-lockers to generate ultrashort laser pulses. Here, we review various aspects of fabrication, characterization, device implementation and operation of nanotube-polymer composites to be used in photonic applications. We also summarize recent results on graphene-based saturable absorbers for ultrafast lasers.

Nanotube–Polymer Composites for Ultrafast Photonics

https://www.ulp.ethz.ch/content/dam/ethz/special-interest/phys/quantum-electronics/ultrafast-laser-physics-dam/publications_awards/publications/2006/248__PhysRep_429__67__2006_.pdf

Passively modelocked surface-emitting semiconductor lasers

We report a ring-cavity thulium fiber laser mode locked with a single-wall carbon nanotube absorber used in transmission. A carboxymethyl cellulose polymer film with incorporated carbon nanotubes synthesized by the arc discharge method has an absorption coinciding with in the amplification bandwidth of a Tm-doped fiber. This laser is pumped by an erbium fiber laser at 1.57 μm wavelength and produces a 37 MHz train of mode-locked 1.32 ps pulses at 1.93 μm wavelength with an average output power of 3.4 mW.

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Mode-locked 1.93 μm thulium fiber laser with a carbon nanotube absorber

Semiconductor saturable absorber mirror (SESAM) devices have become a key component of ultrafast passive mode-locked laser sources Here we describe in more detail how the key SESAM parameters such as saturation fluence, modulation depth, and nonsaturable losses are measured with a high accuracy These parameters need to be known and controlled to obtain stable pulse generation for a given laser A high-precision, wide dynamic range setup is required to measure this nonlinear reflectivity of saturable absorbers The challenge to measure a low modulation depth and key measures necessary to obtain an accurate calibration are described in detail The model function for the nonlinear reflectivity is based on a simple two-level travelling wave system We include spatial beam profiles, nonsaturable losses and higher-order absorption, such as two-photon absorption and other induced absorption Guidelines to extract the key parameters from the measured data are given

/pdf/optical-characterization-of-semiconductor-saturable-4k0u1z9qz3.pdf

Optical characterization of semiconductor saturable absorbers

Summary form only given. We report a self-starting passively mode-locked thulium-doped silica fiber laser capable of 190-fs pulses. Mode-locking of the fiber laser was achieved with a band-gap-engineered saturable absorber fabricated monolithically along with the output coupler of the laser by MOCVD. Stable, single-pulse-in-the-cavity mode-locking was observed for a 2-m-long fiber laser utilizing a nanosecond response strained InGaAs detector.

J. Elliot

Papers

190 fs passively mode-locked thulium fiber laser with low threshold