Low Power Reconfigurability and Reduced Crosstalk in Integrated Photonic Circuits Fabricated by Femtosecond Laser Micromachining

• Published in: Laser & photonics reviews 2020-10, Vol.14 (10), p.n/a
• Main Authors: Ceccarelli, Francesco, Atzeni, Simone, Pentangelo, Ciro, Pellegatta, Francesco, Crespi, Andrea, Osellame, Roberto
• Format: Article
• Language: English
• Subjects: Crosstalk; femtosecond laser micromachining; Integrated circuits; integrated quantum photonics; Laser machining; Lasers; Micromachining; Phase shifters; Photonics; Power; Power management; reconfigurable photonic circuits; thermal phase shifting
• ISSN: 1863-8880; 1863-8899
• DOI: 10.1002/lpor.202000024

Femtosecond laser writing is a powerful technique that allows rapid and cost‐effective fabrication of photonic integrated circuits with unique 3D geometries. In particular, the possibility to reconfigure such devices by thermo‐optic phase shifters represents a paramount feature, exploited to produce adaptive and programmable circuits. However, the scalability is strongly limited by the flaws of current thermal phase shifters, which require hundreds of milliwatts to operate and exhibit large thermal crosstalk. In this work, thermally‐insulating 3D microstructures are exploited to decrease the power needed to induce a 2π phase shift down to 37 mW and to reduce the crosstalk to a few percent. Further improvement is demonstrated when operating in vacuum, with sub‐milliwatt power dissipation and negligible crosstalk. These results pave the way toward the demonstration of complex programmable integrated photonic circuits fabricated by femtosecond laser writing, thus opening exciting perspectives in integrated quantum photonics. Femtosecond laser micromachining allows rapid and cost‐effective fabrication of thermally‐reconfigurable photonic integrated circuits with unique 3D geometries. In this work, thermally‐insulating 3D microstructures are exploited to decrease the power needed to induce a 2π phase shift down to 37 mW and to reduce the thermal crosstalk to a few percent for an interwaveguide separation down to 80 µm.