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.

Unlocking the monolithic integration scenario: optical coupling between GaSb diode lasers epitaxially grown on patterned Si substrates and passive SiN waveguides

Silicon(Si)photonics has recently emerged as a key enabling technology in many application fields thanks to the mature Si process technology,the large silicon wafer size,and promising Si optical properties.The monolithic integration by direct epitaxy of III-V lasers and Si photonic devices on the same Si substrate has been considered for decades as the main obstacle to the realization of dense photonics chips.Despite considerable progress in the last decade,only discrete III-V lasers grown on bare Si wafers have been reported,whatever the wavelength and laser technology.Here we demonstrate the first semiconductor laser grown on a patterned Si photonics platform with light coupled into a waveguide.A mid-IR GaSb-based diode laser was directly grown on a pre-patterned Si photonics wafer equipped with SiN waveguides clad by SiO_(2).Growth and device fabrication challenges,arising from the template architecture,were overcome to demonstrate more than 10 mw outpower of emitted light in continuous wave operation at room temperature.In addition,around 10%of the light was coupled into the SiN waveguides,in good agreement with theoretical calculations for this butt-coupling configuration.This work lft an important building block and it paves the way for future low-cost,large-scale,fully integrated photonic chips.

Mid-infrared Ⅲ-Ⅴ semiconductor lasers epitaxially grown on Si substrates

There is currently much activity toward the integration of mid-infrared semiconductor lasers on Si substrates for developing a variety of smart,compact,sensors based on Si-photonics integrated circuits.We review this rapidly-evolving research field,focusing on the epitaxial integration of antimonide lasers,the only technology covering the whole mid-to-far-infrared spectral range.We explain how a dedicated molecular-beam epitaxy strategy allows for achieving high-performance GaSb-based diode lasers,InAs/AlSb quantum cascade lasers,and InAs/GaInSb interband cascade lasers by direct growth on on-axis(001)Si substrates,whereas GaAs-on-Si or GaSb-on-Si layers grown by metal-organic vapor phase epitaxy in large capability epitaxy tools are suitable templates for antimonide laser overgrowth.We also show that etching the facets of antimonide lasers grown on Si is a viable approach in view of photonic integrated circuits.Remarkably,this review shows that while diode lasers are sensitive to residual crystal defects,the quantum cascade and interband cascade lasers grown on Si exhibit performances comparable to those of similar devices grown on their native substrates,due to their particular band structures and radiative recombination channels.Long device lifetimes have been extrapolated for interband cascade lasers.Finally,routes to be further explored are also presented.