It has been a long-standing challenge to produce air-stable few- or monolayer samples of phosphorene because thin phosphorene films degrade rapidly in ambient conditions. Here we demonstrate a new highly controllable method for fabricating high quality, air-stable phosphorene films with a designated number of layers ranging from a few down to monolayer. Our approach involves the use of oxygen plasma dry etching to thin down thick-exfoliated phosphorene flakes, layer by layer with atomic precision. Moreover, in a stabilized phosphorene monolayer, we were able to precisely engineer defects for the first time, which led to efficient emission of photons at new frequencies in the near infrared at room temperature. In addition, we demonstrate the use of an electrostatic gate to tune the photon emission from the defects in a monolayer phosphorene. This could lead to new electronic and optoelectronic devices, such as electrically tunable, broadband near infrared lighting devices operating at room temperature.

A low-loss suspended core As₃₈Se₆₂ fiber with core diameter of 4.5 μm and a zero-dispersion wavelength of 3.5 μm was used for mid-infrared supercontinuum generation. The dispersion of the fiber was measured from 2.9 to 4.2 μm and was in good correspondence with the calculated dispersion. An optical parametric amplifier delivering 320 fs pulses with a peak power of 14.8 kW at a repetition rate of 21 MHz was used to pump 18 cm of suspended core fiber at different wavelengths from 3.3 to 4.7 μm. By pumping at 4.4 μm with a peak power of 5.2 kW coupled to the fiber a supercontinuum spanning from 1.7 to 7.5 μm with an average output power of 15.6 mW and an average power >5.0 μm of 4.7 mW was obtained.

We report measurements of the third order optical nonlinearity of 51 chalcogenide glasses in the near infrared. Substituting more polarizable elements (Se for S, Sb for As) into the glasses increased their nonlinearity but also reduced the optical bandgap increasing two-photon absorption. Overall the measured values are an extremely good fit to the semi-empirical Miller’s rule whilst the normalized real and imaginary parts are in satisfactory agreement with the scaling for indirect gap semiconductors reported by Dinu. At 1550nm we find that there is an upper limit to the nonlinearity of ≈10⁻¹³cm²/W above which two-photon absorption becomes significant.

We report the characteristics of low-loss chalcogenide waveguides for sensing in the mid-infrared (MIR). The waveguides consisted of a Ge_11.5As₂₄Se_64.5 rib waveguide core with a 10nm fluoropolymer coating on a Ge_11.5As₂₄S_64.5 bottom cladding and were fabricated by thermal evaporation, photolithography and ICP plasma etching. Over most of the functional group band from 1500 to 4000cm⁻¹ the losses were < 1dB/cm with a minimum of 0.3dB/cm at 2000cm⁻¹. The basic capabilities of these waveguides for spectroscopy were demonstrated by measuring the absorption spectrum of soluble Prussian blue in Dimethyl Sulphoxide.

We review experiments on mid-infrared supercontinuum (SC) generation including our own work on chalcogenide waveguides. Simulations are used to define the conditions in which a chalcogenide waveguide would produce SC from ≈2.5 µm to beyond 10 µm in a single waveguide device. The simulations suggested that broadband SC could be generated by pumping a bulk chalcogenide with fs pulses in the anomalous dispersion regime and this was demonstrated experimentally by producing a flat SC from 2.5 µm to beyond 7.5 µm.

By pumping an 11-cm-long step-index chalcogenide fiber with $\sim 330\mathrm{fs}$ pulses at 4.0 μm from an optical parametric amplifier, mid-infrared supercontinuum generation spanning from $\sim 1.8$ to $\sim 10\mathrm{\mu m}$ within a dynamic range of $\pm 15\mathrm{dB}$ has been demonstrated at a relatively low power threshold of $\sim 3000\mathrm{W}$.