Monolithic frequency comb platform based on interband cascade lasers and detectors

Funding: Austrian Science Fund (FWF) within the projects "NanoPlas" (P28914-N27), "Building Solidsfor Function" (Project W1243), "NextLite" (F4909-N23), as well as by the Austrian Research Promotion Agency through the ERA-Net Photonic Sensing program, project "ATMO-SENSE" (FFG:861581). H.D. was supported by the ESF project CZ.02.2.69/0.00.0/16_027/0008371. A.M.A was supported by the projects COMTERA - FFG 849614 and AFOSR FA9550-17-1-0340.New insights into the laser dynamics of interband cascade lasers reveal the possibility to generatefrequency modulated combs by utilizing their inherent gain nonlinearity. The resultingcomb state is characterized by chirped instantaneous frequency, which appears to be universalto frequency combs based on gain induced four-wave mixing. The fast dynamics in the injectorsfurther allow the realization of exceptionally sensitive and high-speed photodetectors,operating at room-temperature, using the very same epilayer structure. With the capability ofintegrating frequency combs and ultra-fast detectors on a single chip consuming less than awatt of electric power, interband cascade laser technology provides a complete and unmatchedplatform for future monolithic and battery-driven dual-comb spectrometers.Publisher PDFPeer reviewe

Picosecond pulses from a mid-infrared interband cascade laser

Funding: Austrian Science Fund (F4909-N23, P28914-N27,W1243); Österreichische Forschungsförderungsgesellschaft (ATMO-SENSE, ERANet Photonic Sensing program, COMTERA-FFG849614); European Science Foundation (ESF) (CZ.02.2.69/0.0/0.0/16_027/0008371); Air Force Office of Scientific Research(AFOSR FA9550-17-1-0340).The generation of mid-infrared pulses in monolithic and electrically pumped devices is of great interest for mobile spectroscopic instruments. The gain dynamics of interband cascade lasers (ICL) are promising for mode-locked operation at low threshold currents. Here, we present conclusive evidence for the generation of picosecond pulses in ICLs via active mode-locking. At small modulation power, the ICL operates in a linearly chirped frequency comb regime characterized by strong frequency modulation. Upon increasing the modulation amplitude, the chirp decreases until broad pulses are formed. Careful tuning of the modulation frequency minimizes the remaining chirp and leads to the generation of 3.2 ps pulses.Publisher PDFPeer reviewe

Inverse Bandstructure Engineering of Alternative Barrier Materials for InGaAs-based Terahertz Quantum Cascade Lasers

The final publication is available via https://doi.org/10.1109/CLEOE-EQEC.2017.8086449.Quantum cascade lasers (QCLs) are compact and powerful sources that cover a wide spectral range from infrared to terahertz (THz) radiation. The emission characteristics of QCLs depend on design parameters such as layer thickness, material composition and doping. Therefore, the material system has to be chosen accurately. This paper implemented an inverse quantum engineering algorithm to investigate the influence of the barrier material on the lasing performance and characteristics of THz active regions. Starting from an original design, barrier materials are exchanged while the wave functions are kept constant. A systematic comparison between material systems such as InGaAs/InAlAs, InGaAs/GaAsSb and InGaAs/InAlGaAs was performed with focus on quantum transport and optical gain. The quantum design with the wave functions, the electrical and the optical properties of two InGaAs-based devices, one of which is employs ternary InAlAs barriers, whereas the other device employs quaternary InAlGaAs barriers is presented. As designed, the algorithm leads to almost identical wave functions for different barrier thickness due to the different CBOs of the investigated materials. Results find that thin barrier devices employing ternary barrier materials such as InAlAs show the highest optical gain. Consequently the InGaAs/InAlAs material system, which is already commonly used for mid-infrared quantum cascade lasers, is also very well suited for high performance THz QCLs

Microcavity-integrated graphene photodetector

The monolithic integration of novel nanomaterials with mature and established technologies has considerably widened the scope and potential of nanophotonics. For example, the integration of single semiconductor quantum dots into photonic crystals has enabled highly efficient single-photon sources. Recently, there has also been an increasing interest in using graphene - a single atomic layer of carbon - for optoelectronic devices. However, being an inherently weak optical absorber (only 2.3 % absorption), graphene has to be incorporated into a high-performance optical resonator or waveguide to increase the absorption and take full advantage of its unique optical properties. Here, we demonstrate that by monolithically integrating graphene with a Fabry-Perot microcavity, the optical absorption is 26-fold enhanced, reaching values >60 %. We present a graphene-based microcavity photodetector with record responsivity of 21 mA/W. Our approach can be applied to a variety of other graphene devices, such as electro-absorption modulators, variable optical attenuators, or light emitters, and provides a new route to graphene photonics with the potential for applications in communications, security, sensing and spectroscopy.Comment: 19 pages, 4 figure