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Direct-Laser-Written Polymer Nanowire Waveguides for Broadband Single Photon Collection from Epitaxial Quantum Dots into a Gaussian-like Mode



Edgar Perez, Cori Haws, Marcelo Davanco, Jindong Song, Luca Sapienza, Kartik Srinivasan


Single epitaxial quantum dots (QDs) are a leading technology for quantum light generation, particularly when they are embedded in photonic geometries that enhance their emission into a targeted and confined mode. However, coupling this mode into a desirable downstream optical channel, such as a single mode fiber or a free-space Gaussian beam, often remains challenging. Direct laser writing (DLW) enables the fabrication of three-dimensional sub-micron features out of photoresist, supporting flexibility in the design of micro- and nano- scale devices that can interface with quantum emitters and address this challenge. In this study, we use DLW to directly waveguide-couple epitaxially-grown InAs/GaAs QDs by fabricating < 1 µ m diameter polymer nanowires (PNWs) in direct contact with the GaAs substrate housing the QDs. The PNWs are high index contrast cylindrical waveguides, perpendicular to the GaAs device layer, which couple the emission from an underlying QD to the HE 11 mode of the PNW, enhancing the collection efficiency to a single-mode fiber. PNW fabrication does not alter the QD device layer (e.g., via etching), making PNWs especially well suited for augmenting existing photonic geometries that enhance QD emission. We study the use of PNWs as standalone devices and in conjunction with metallic nanorings, the latter being an already-established geometry for increasing vertical extraction of light from an embedded QD. Since the PNWs are fabricated on substrates that are absorbing and reflecting at the DLW exposure wavelength, we report on methods to mitigate standing wave reflections and heat, which otherwise prevent PNW fabrication. We observe a factor of ( 3.0 ± 0.7)× improvement in a nanoring system with a PNW compared to the same system without a PNW, in line with numerical results, highlighting a PNW's ability to waveguide QD emission and increase collection efficiency simultaneously. These results demonstrate a new approach in which DLW can provide additional functionality for quantum emitter photonics, in a manner compatible with existing top-down fabrication approaches
Advanced Quantum Technologies


direct laser writing, quantum dots, nanowires, optical modes, single photon, single photon collection, waveguide, broadband single photon collection, polymer nanowire, polymer waveguide, quantum emitter


Perez, E. , Haws, C. , Davanco, M. , Song, J. , Sapienza, L. and Srinivasan, K. (2023), Direct-Laser-Written Polymer Nanowire Waveguides for Broadband Single Photon Collection from Epitaxial Quantum Dots into a Gaussian-like Mode, Advanced Quantum Technologies, [online],, (Accessed May 18, 2024)


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Created November 16, 2023, Updated April 11, 2024