Abstract
Interfacing integrated on-chip waveguides with spectroscopic approaches represents one research direction within current photonics aiming at reducing geometric footprints and increasing device densities. Particularly relevant is to connect chip-integrated waveguides with established fiber-based circuitry, opening up the possibility for a new class of devices within the field of integrated photonics. Here, one attractive waveguide is the on-chip light cage, confining and guiding light in a low-index core through the anti-resonance effect. This waveguide, implemented via 3D nanoprinting and reaching nearly 100% overlap of mode and material of interest, uniquely provides side-wise access to the core region through the open spaces between the cage strands, drastically reducing gas diffusion times. Here, we extend the capabilities of the light cage concept by interfacing light cages and optical fibers, reaching a fully fiber-integrated on-chip waveguide arrangement with its spectroscopic capabilities demonstrated here on the example of tunable diode laser absorption spectroscopy of ammonia. Controlling and optimizing the fiber circuitry integration have been achieved via automatic alignment in etched v-grooves on silicon chips. This successful device integration via 3D nanoprinting highlights the fiber-interfaced light cage to be an attractive waveguide platform for a multitude of spectroscopy-related fields, including bio-analytics, lab-on-chip photonic sensing, chemistry, and quantum metrology.
Highlights
Sensing of gases is important for many areas of science and technology, such as pollution monitoring in environmental research1 or breath analysis in life science.2 In general, gases can be detected by using sensors based on different techniques, examples of which include semiconducting metal oxide sensors,3–5 catalytic sensors,6 and optical sensors.7One highly relevant approach is tunable diode laser absorption spectroscopy (TDLAS), a widely used optical sensing technique that can achieve fast, selective, and reliable sensing of trace gases via spectroscopic detection of molecular fingerprints.8–10 The sensitivity of TDLAS can be enhanced by integrated waveguides, providing significantly longer light–matter interaction lengths compared to free-space configurations.From the perspective of fiber optics, microstructured optical fibers (MOFs) and post-processed fibers have been employed for gas sensing in chemical and biological applications,11–14 while recently hollow-core-type MOFs have gained substantial attraction due to simplified fabrication.15,16 Gas sensing applications have successfully been demonstrated in hollow-core MOFs, such as Kagomé-type fibers17 and photonic bandgap fibers,18–20 with near 100% spatial scitation.org/journal/app overlap between light and gas, allowing for the direct use of the Lambert–Beer law without the knowledge of the modal fields
In this Letter, we demonstrate the successful interfacing of light cages with fiber circuitry and in-line ammonia gas sensing using tunable diode laser absorption spectroscopy (TDLAS) at the near infrared (NIR) wavelength [Figs. 1(a) and 1(d)]
We demonstrated the integration of light cage sensing structures into a conventional fiber-based probing setup based on conventional optical fibers
Summary
Sensing of gases is important for many areas of science and technology, such as pollution monitoring in environmental research1 or breath analysis in life science.2 In general, gases can be detected by using sensors based on different techniques, examples of which include semiconducting metal oxide sensors,3–5 catalytic sensors,6 and optical sensors.7One highly relevant approach is tunable diode laser absorption spectroscopy (TDLAS), a widely used optical sensing technique that can achieve fast, selective, and reliable sensing of trace gases via spectroscopic detection of molecular fingerprints.8–10 The sensitivity of TDLAS can be enhanced by integrated waveguides, providing significantly longer light–matter interaction lengths compared to free-space configurations.From the perspective of fiber optics, microstructured optical fibers (MOFs) and post-processed fibers have been employed for gas sensing in chemical and biological applications,11–14 while recently hollow-core-type MOFs have gained substantial attraction due to simplified fabrication.15,16 Gas sensing applications have successfully been demonstrated in hollow-core MOFs, such as Kagomé-type fibers17 and photonic bandgap fibers,18–20 with near 100% spatial scitation.org/journal/app overlap between light and gas, allowing for the direct use of the Lambert–Beer law without the knowledge of the modal fields. The maximum length of the light cage achieved so far is 3 cm, yielding single-strand aspect ratios as high as 8300.37 Specific features of the light cage concept relevant within the context of absorption spectroscopy are (i) close-to-unity overlap of the electromagnetic field with the core material, (ii) diffraction-less guidance over centimeter distances, FIG.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
