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The broadband electroluminescence of a quantum cascade device based on a multi-color active region covering the wavelengths 5.9 μm - 7.2 μm was measured. Anti-reflection coatings were applied on both cleaved facets to remove the Fabry-Pérot cavity and prevent the device from lasing. This allows the latter to be studied either as a superluminescent diode or a single-pass amplifier in order to determine its suitability as a source for low speckle imaging applications. At 243 K, the amplified spontaneous emission has a peak power of 38 μW that agrees well with a simple model of spontaneous emission intensity. The light of a similar structure could be modulated up to 1 GHz, limited by the RC constant of the device. The peak gain was measured from high-resolution luminescence spectra and determined to be 6.3 cm⁻¹, corresponding to a single-pass gain of 1.89.

We present an aspheric collimating lens for mid-infrared (4-14 µm) quantum cascade lasers. The lenses were etched into silicon by an inductively coupled plasma reactive ion etching system on wafer level. The high refractive index of silicon reduces the height of the lens profile resulting in a simple element working at high numerical aperture (up to 0.82). Wafer level processes enable the fabrication of about 5000 lenses in parallel. Such cost-effective collimating lens is a step towards the adoption of quantum cascade lasers for all its potential applications.

We report on the fabrication and optical characterization of a switchable photonic crystal nanocavity actuated by liquid crystals. This device acts as a filter presenting a transmission peak around the telecom wavelength λ = 1550 nm. Passing from the isotropic to the anisotropic (oriented crystals) state of the liquid crystals, a shift of ∆λ = 13 nm has been measured, which confirms the theoretical predictions obtained by finite difference time domain simulations. We have developed a photonic crystal nanocavity that can be tuned thanks to the properties of liquid crystals infiltrated in the holes of the photonic device.

A subwavelength-scale square lattice optical nanostructure is fabricated using an interference photolithography process on the surface of a quartz microlens array. This nanostructuring of the quartz surface introduces an antireflective effect, reducing reflectivity between 10% and 30% and enhancing the transmissivity 3% in the visible spectrum. This approach permits fast fabrication on a 4-inch wafer covered with microlenses (non-flat surface) and produces monolithic devices which are robust to adverse environments such as temperature variations.