Interband cascade technology for energy-efficient mid-infrared free-space communication

Space-to-ground high-speed transmission is of utmost importance for the development of a worldwide broadband network.Mid-infrared wavelengths offer numerous advantages for building such a system,spanning from low atmospheric attenuation to eye-safe operation and resistance to inclement weather conditions.We demonstrate a full interband cascade system for high-speed transmission around a wavelength of 4.18μm.The low-power consumption of both the laser and the detector in combination with a large modulation bandwidth and sufficient output power makes this technology ideal for a free-space optical communication application.Our proof-of-concept experiment employs a radio-frequency optimized Fabry–Perot interband cascade laser and an interband cascade infrared photodetector based on a type-II InAs/GaSb superlattice.The bandwidth of the system is evaluated to be around 1.5 GHz.It allows us to achieve data rates of 12 Gbit/s with an on–off keying scheme and 14 Gbit/s with a 4-level pulse amplitude modulation scheme.The quality of the transmission is enhanced by conventional pre-and post-processing in order to be compatible with standard error-code correction.

Advanced mid-infrared plasmonic waveguides for on-chip integrated photonics

Long-wave infrared(LWIR, 8–14 μm) photonics is a rapidly growing research field within the mid-IR with applications in molecular spectroscopy and optical free-space communication. LWIR applications are often addressed using rather bulky tabletop-sized free-space optical systems, preventing advanced photonic applications,such as rapid-time-scale experiments. Here, device miniaturization into photonic integrated circuits(PICs) with maintained optical capabilities is key to revolutionize mid-IR photonics. Subwavelength mode confinement in plasmonic structures enabled such miniaturization approaches in the visible-to-near-IR spectral range. However,adopting plasmonics for the LWIR needs suitable low-loss and-dispersion materials with compatible integration strategies to existing mid-IR technology. In this paper, we further unlock the field of LWIR/mid-IR PICs by combining photolithographic patterning of organic polymers with dielectric-loaded surface plasmon polariton(DLSPP) waveguides. In particular, polyethylene shows favorable optical properties, including low refractive index and broad transparency between ~2 μm and 200 μm. We investigate the whole value chain, including design, fabrication, and characterization of polyethylene-based DLSPP waveguides and demonstrate their first-time plasmonic operation and mode guiding capabilities along S-bend structures. Low bending losses of ~1.3 d B and straight-section propagation lengths of ~1 mm, pave the way for unprecedented complex on-chip mid-IR photonic devices. Moreover, DLSPPs allow full control of the mode parameters(propagation length and guiding capabilities) for precisely addressing advanced sensing and telecommunication applications with chip-scale devices.