Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC)
Femtosecond Laser Inscription of Integrated Diamond Quantum Photonics for Quantum Information and Sensing
Vibhav Bharadwaj, Thien Le Phu, Paul E. Barclay, Roberta Ramponi, Angelo Bifone, Shane Michael Eaton, John Patrick Hadden, Maria Ramos, Argyro N. Giakoumaki, Ottavia Jedrkiewicz, Rakshyakar Giri, Federico Gorrini, Luca Basso, Belén Sotillo
Apart from the outstanding perfect-for-application properties of optical transparency, hardness, bio-inertness and thermal conductivity of diamond, it has interested the scientific community due to a naturally occurring imperfection, the Nitrogen Vacancy (NV) color center. The NV center has emerged as an encouraging candidate for quantum computing due to its long electron spin coherence times and its ability to be found, manipulated and read out optically [1]. Additionally, the spin states are sensitive to magnetic and electric fields through the Zeeman and Stark effects, respectively and hence pose as a notable substrate for field sensing applications.
Apart from the outstanding perfect-for-application properties of optical transparency, hardness, bio-inertness and thermal conductivity of diamond, it has interested the scientific community due to a naturally occurring imperfection, the Nitrogen Vacancy (NV) color center. The NV center has emerged as an encouraging candidate for quantum computing due to its long electron spin coherence times and its ability to be found, manipulated and read out optically [1]. Additionally, the spin states are sensitive to magnetic and electric fields through the Zeeman and Stark effects, respectively and hence pose as a notable substrate for field sensing applications.
Diamond is an exceptional material due to its hardness, high thermal conductivity and transparency from the UV to far IR. Recently it has caught the attention of the scientific community because it is the host of different color centers that can be used for magnetic sensing applications and quantum computing [1]. One of the most promising of these defects is the nitrogen-vacancy (NV) center. The electrons of the NV center, largely localized at the vacancy site, combine to form a spin triplet, which can be polarized with 532-nm laser light. The NV's states are isolated from environmental perturbations, making their spin coherence times long even at room temperature. The NVs can be easily initialized, manipulated and read out using light. Therefore, an important breakthrough would be in connecting, using optical waveguides, multiple diamond NVs.
Integrated photonic circuits promise to be foundational for applications in quantum information and sensing technologies, through their ability to confine and manipulate light. A key role in such technologies may be played by spin-active quantum emitters, which can be used to store quantum information or as sensitive probes of the local environment. A leading candidate is the negatively charged nitrogen vacancy (NV−) diamond color center, whose ground spin state can be optically read out, exhibiting long (≈1 ms) coherence times at room temperature. These properties have driven research toward the integration of photonic circuits in the bulk of diamond with the development of techniques allowing fabrication of optical waveguides. In particular, femtosecond laser writing has emerged as a powerful technique, capable of writing light guiding structures with 3D configurations as well as creating NV complexes. In this Perspective, the physical mechanisms behind laser fabrication in diamond will be reviewed. The properties of waveguides, single- and ensemble-NV centers, will be analyzed, together with the possibility to combine such structures in integrated photonic devices, which can find direct application in quantum information and sensing.
Diamond’s nitrogen-vacancy (NV) center has been shown as a promising candidate for sensing applications and quantum computing because of its long electron spin coherence time and its ability to be found, manipulated and read out optically. An integrated photonics platform in diamond would be useful for NV-based magnetometry and quantum computing, in which NV centers are optically linked for long-range quantum entanglement due to the integration and stability provided by monolithic optical waveguides. Surface microchannels in diamond would be a great benefit for sensing applications, where NV centers could be used to probe biomolecules. In this work, we applied femtosecond laser writing to form buried 3D optical waveguides in diamond. By engineering the geometry of the type II waveguide, we obtained single mode guiding from visible to the infrared wavelengths. Further, we demonstrate the first Bragg waveguide in bulk diamond with narrowband reflection. We show the formation of single, high quality NV centers on demand in ultrapure diamond using a single pulse from a femtosecond laser. With these building blocks in place, we fabricated an integrated quantum photonic circuit containing optical waveguides coupled to NV centers deterministically placed within the waveguide. The single NVs were excited and their emission collected by the optical waveguides, allowing easy interfacing to standard optical fibers. We also report high aspect ratio surface microchannels, which we will integrate with laser-written NVs and waveguides, paving the way for ultrasensitive, nanoscale resolution biosensors.
Abstract Diamond has attracted great interest as a quantum technology platform thanks to its optically active nitrogen vacancy (NV) center. The NV's ground state spin can be read out optically, exhibiting long spin coherence times of ≈1 ms even at ambient temperatures. In addition, the energy levels of the NV are sensitive to external fields. These properties make NVs attractive as a scalable platform for efficient nanoscale resolution sensing based on electron spins and for quantum information systems. Diamond photonics enhance optical interactions with NVs, beneficial for both quantum sensing and information. Diamond is also compelling for microfluidic applications due to its outstanding biocompatibility, with sensing functionality provided by NVs. However, it remains a significant challenge to fabricate photonics, NVs, and microfluidics in diamond. In this Progress Report, an overview is provided of ion irradiation and femtosecond laser writing, two promising fabrication methods for diamond‐based quantum technological devices. The unique capabilities of both techniques are described, and the most important fabrication results of color center, optical waveguide, and microfluidics in diamond are reported, with an emphasis on integrated devices aiming toward high performance quantum sensors and quantum information systems of tomorrow.
Femtosecond laser writing and ion irradiation have been demonstrated as powerful fabrication tools for integrated quantum photonics in diamond in article no. 1900006. The figure depicts femtosecond laser inscription and ion beam irradiation in diamond, which can be applied separately, or potentially together, to accurately form nitrogen vacancy (NV) center defects within synthetic diamond. The nitrogen (shown as yellow sphere)–vacancy (shown as light pink sphere) color center defect in the tetrahedral lattice of carbons (shown as black spheres) has emerged as a suitable candidate for a qubit (represented by the Bloch sphere above the diamond) for quantum information and field sensing applications. In addition, the article highlights the latest results on laser and ion beam irradiation fabrication of integrated photonic and microfluidic components in diamond for interfacing with NV centers.
Point defects in diamond, particularly nitrogen-vacancy (NV) centers, have emerged as powerful tools for a broad range of quantum technologies. These defects are promising candidates for quantum information science, serving as deterministic single-photon sources and solid-state quantum memories. They have also been employed as nanoscale quantum sensors to detect various physical quantities, including magnetic fields, electric fields, and temperature, owing to their long spin coherence time at room temperature. Development of these diamond-based quantum technologies has been rapidly boosted by a recent quantum leap in nanofabrication technologies for high-quality single-crystal diamond. Incorporating these color centers into diamond nanostructures with mature integrated photonics provides a promising route to build scalable and practical systems for quantum applications. This review discusses recent progress and challenges in the hybrid integration of diamond color centers on cutting-edge photonic platforms. Nitrogen-vacancy centers in diamond have emerged as powerful tools for a broad range of quantum technologies. This review discusses recent progress and challenges in the hybrid integration of diamond color centers on cutting-edge photonic platforms.