Interband Cascade Photonic Integrated Circuits on Native III-V Chip

Abstract

We describe how a midwave infrared photonic integrated circuit (PIC) that combines lasers, detectors, passive waveguides, and other optical elements may be constructed on the native GaSb substrate of an interband cascade laser (ICL) structure. The active and passive building blocks may be used, for example, to fabricate an on-chip chemical detection system with a passive sensing waveguide that evanescently couples to an ambient sample gas. A variety of highly compact architectures are described, some of which incorporate both the sensing waveguide and detector into a laser cavity defined by two high-reflectivity cleaved facets. We also describe an edge-emitting laser configuration that optimizes stability by minimizing parasitic feedback from external optical elements, and which can potentially operate with lower drive power than any mid-IR laser now available. While ICL-based PICs processed on GaSb serve to illustrate the various configurations, many of the proposed concepts apply equally to quantum-cascade-laser (QCL)-based PICs processed on InP, and PICs that integrate III-V lasers and detectors on silicon. With mature processing, it should become possible to mass-produce hundreds of individual PICs on the same chip which, when singulated, will realize chemical sensing by an extremely compact and inexpensive package.

Integrated Photonics Packaging: Challenges and Opportunities

“…Integration of mid-IR light sources (quantum cascade lasers and interband cascade lasers) with PICs have also been demonstrated through both monolithic − and hybrid approaches. − Photonic packaging in the mid-IR, nonetheless, is still hampered by the fact that most packaging materials, in particular epoxy adhesives, become optically opaque at longer wavelengths . As a result, significant challenges arise for interfacing chip I/O with fiber optics, attachment of micro-optical elements, as well as integration and sealing of fluidic/gas channels .…”

Integrated Nanophotonic Waveguide-Based Devices for IR and Raman Gas Spectroscopy

“…This typically stems from the mode mismatch and misalignment between the active and passive sections of the chips, i.e., the laser cavity and the passive waveguide. For improving the coupling efficiency between the waveguide and the light sources, the usage of distributed Bragg reflectors (DBR) or appropriate mode profile engineering has been proposed [148]. Separate prototypes of integrations of the laser and the waveguide, the waveguide and the detector, the laser and detector are found in the literature; however, complete integration of all the three components in a single chip is still an active and ongoing pursuit, with very few actual demonstrations.…”

“…In order to improve the performance further, distributed Bragg reflectors (DBR), high reflectivity coatings, or simply etched or cleaved facets that ensure multiple passes through the active region have been proposed for a waveguide-integrated ICD. Such a design simultaneously increases quantum efficiency, as well as reducing dark current [148].…”

“…Another strategy to improve the compactness and robustness of the IR spectroscopy setup is to design the sensing functionality within the cavity of the laser, as demonstrated through intra-cavity laser absorption spectroscopy [148,170]. The in situ detection of chemical species within the laser cavity can be monitored directly through the laser's I-V characteristics, which can even eliminate the use of a separate detector [170].…”

Resonant cavity infrared detectors for scalable gas sensing

“…Such semiconductor chips would consist of a light source, optical path, and optical detector all integrated into a single photonic integrated circuit (PIC). 1 Current low-cost optical gas sensors use broadband sources, such as thermal IR emitters 2 or LEDs, 3,4 together with optical bandpass filters. Gas concentration is related to the amount of light absorbed by gas molecules in the optical path over the entire broadband spectrum of light measured by the detector.…”