No abstract

Nature provides a set of solutions for photonic structures that are finely tuned, organically diverse, and optically efficient. Exquisite knowledge of structure−property relationships in proteins aids in the design of materials with desired properties for building devices with novel functionalities, which are difficult to achieve or previously unattainable.Here we report whispering-gallery-mode (WGM) microresonators fabricated entirely from semicrystalline structural proteins (i.e., squid ring teeth, SRT, from Loligo vulgaris and its recombinant) with quality factors as high as 10 5 . We first demonstrate versatility of protein-based devices via facile doping, engaging secondary structures. Then we investigate thermorefractivity and find that it increases with β-sheet crystallinity, which can be altered by methanol exposure and is higher in the selected recombinant SRT protein than its native counterpart. We present a set of photonic devices fabricated from SRT proteins such as add-drop filters and fibers. Protein-based microresonators demonstrated in this work are highly flexible and robust where quality factors and spectral position of resonances are unaffected from mechanical strain. We find that the thermooptic coefficients of SRT proteins are nearly 100× larger than silica and more than 10× larger than polydimethylsiloxane. Finally, we demonstrate an optical switch utilizing the surprisingly large thermorefractivity of SRT proteins. Achieving 41 dB isolation at an input power of 1.44 μW, all-protein optical switch is 10× more energy efficient than a conventional (silica) thermo-optic switch.

Integrating solid-state quantum emitters with nanophotonic resonators is essential for efficient spinphoton interfacing and optical networking applications. While diamond color centers have proven to be excellent candidates for emerging quantum technologies, their integration with optical resonators remains challenging. Conventional approaches based on etching resonators into diamond often negatively impact color center performance and offer low device yield. Here, we developed an integrated photonics platform based on templated atomic layer deposition of TiO2 on diamond membranes. Our fabrication method yields high-performance nanophotonic devices while avoiding etching wavelength-scale features into diamond. Moreover, this technique generates highly reproducible optical resonances and can be iterated on individual diamond samples, a unique processing advantage. Our approach enables highcooperativity interfacing between cavity photons and coherent color centers, opening a new pathway for integrated quantum photonics.