Sounak Mukherjee, Zi-Huai Zhang, Daniel G. Oblinsky, M. de Vries, Brett C. Johnson, Brant C. Gibson, Edwin Lawrence Harrop Mayes, Andrew Mark Edmonds, Nicola Palmer, Matthew Markham, Ádám Gali, Gergő Thiering, Adam Dalis, Timothy F. Dumm, Gregory D. Scholes, Alastair D. Stacey, Philipp Reineck, Nathalie P. de Leon
Color centers in diamond are promising platforms for quantum technologies. Most color centers in diamond discovered thus far emit in the visible or near-infrared wavelength range, which are incompatible with long-distance fiber communication and unfavorable for imaging in biological tissues. Here, we report the experimental observation of a new color center that emits in the telecom O-band, which we observe in silicon-doped bulk single crystal diamonds and microdiamonds. Combining absorption and photoluminescence measurements, we identify a zero-phonon line at 1221 nm and phonon replicas separated by 42 meV. Using transient absorption spectroscopy, we measure an excited state lifetime of around 270 ps and observe a long-lived baseline that may arise from intersystem crossing to another spin manifold.
Color centers in diamond are promising platforms for quantum technologies. Most color centers in diamond discovered thus far emit in the visible or near-infrared wavelength range, which are incompatible with long-distance fiber communication and unfavorable for imaging in biological tissues. Here, we report the experimental observation of a new color center that emits in the telecom O-band, which we observe in silicon-doped bulk single crystal diamonds and microdiamonds. Combining absorption and photoluminescence measurements, we identify a zero-phonon line at 1221 nm and phonon replicas separated by 42 meV. Using transient absorption spectroscopy, we measure an excited state lifetime of around 270 ps and observe a long-lived baseline that may arise from intersystem crossing to another spin manifold.
Solid-state color centers in diamond are promising candidates for quantum communication, yet the absence of intrinsic emitters operating in the telecom band has remained a fundamental bottleneck for scalable fiber-based quantum networks compatible with the existing optical fiber infrastructure. Here, by combining first-principles calculations with group-theoretical analysis, we establish a general chemical design rule that links the chemical nature of substitutional impurities to the zero-phonon line (ZPL) wavelengths of vacancy-impurity-vacancy centers in diamond. This framework shows that impurity atomic size and orbital energies act together to tune the ZPL. Specifically, heavy elements with fully filled d orbitals yielding shorter-wavelength emission, while lighter elements lacking occupied d orbitals, generate longer-wavelengths. Guided by this principle, we identify the negatively charged vacancy-magnesium-vacancy (MgV3−) center as an ideal telecom-band emitter at 1448 nm, exhibiting outstanding optical coherence, minimal electron−phonon coupling, and a remarkably high Debye−Waller factor of 94.1%. These results provide not only a long-sought candidate for fiber-compatible quantum emitters but also a transferable design paradigm for tailoring optical transitions in wide-bandgap hosts, paving the way for material discovery in solid-state quantum technologies.
Abstract This study presents a detailed investigation into the fluorescence properties of color centers in single-crystal diamond needles (SCDNs) synthesized via chemical vapor deposition. Using steady-state and time-resolved photoluminescence (PL) techniques, we identified color centers with zero-phonon lines at 389 nm, 468 nm, 575 nm (NV0), 637 nm (NV–), and 738 nm (SiV–). PL excitation spectroscopy conducted at room temperature revealed the complex electronic structure of some of these centers, paving the way for further investigation into their fluorescence properties. Lifetime measurements were performed for each center, with the 389 nm one exhibiting the longest decay time (∼30 ns), which is advantageous for enhancing quantum coherence, improving photon emission efficiency, and reducing power consumption. Altogether, these findings highlight the potential of SCDNs for quantum applications and confirm their promise as a platform for next-generation photonic and quantum devices.
Abstract Color centers in the O-band (1260–1360 nm) are crucial for realizing long-coherence quantum network nodes in memory-assisted quantum communications. However, only a limited number of O-band color centers have been thoroughly explored in silicon hosts as spin-photon interfaces. This study explores and compares two promising O-band color centers in silicon for high-fidelity spin-photon interfaces: T and *Cu (transition metal) centers. During T center generation process, we observed the formation and dissolution of other color centers, including the copper-silver related centers with a doublet line around 1312 nm (* Cun0 Cu n 0 ), near the optical fiber zero dispersion wavelength (around 1310 nm). We then investigated the photophysics of both T and *Cu centers, focusing on their emission spectra and spin properties. The * Cu00 Cu 0 0 line under a 0.5 T magnetic field demonstrated a 25% broadening, potentially due to spin degeneracy, suggesting that this center can be a promising alternative to T centers.
Color centers in diamond are important quantum emitters for a broad range of applications ranging from quantum sensing to quantum optics. Understanding the internal energy level structure is of fundamental importance for future applications. We experimentally investigate the level structure of an ensemble of few negatively charged silicon-vacancy (SiV − ) and germanium-vacancy (GeV − ) centers in bulk diamond at room temperature by photoluminescence (PL) and excitation (PLE) spectroscopy over a broad wavelength range from 460 to and perform power-dependent saturation measurements. For SiV − our experimental results confirm the presence of a higher energy transition at . By comparison with detailed theoretical simulations of the imaginary dielectric function we interpret the transition as a dipole-allowed transition from -state to -state where the corresponding a 2 u -level lies deeply inside the diamond valence band. Therefore, the transition is broadened by the diamond band. At higher excitation power of we indicate signs of a parity-conserving transition at supported by saturation measurements. For GeV − we demonstrate that the PLE spectrum is in good agreement with the mirror image of the PL spectrum of the zero-phonon line. Experimentally we do not observe a higher lying energy level up to a transition wavelength of . The observed PL spectra are identical, independent of excitation wavelength, suggesting a rapid decay to excited state and followed by optical transition to ground state. Our investigations convey important insights for future quantum optics and quantum sensing experiments based on SiV − -center and GeV − -center in diamond.
Color centers in diamond are a promising platform for quantum communication, as they can serve as solid state quantum memories with efficient optical transitions. Much recent attention has focused on the negatively charged NV center in diamond, which has a spin triplet ground state electronic configuration that can be measured and initialized optically, exhibits long spin coherence times at room temperature, and has narrow, spin-conserving optical transitions. However, the NV center exhibits a large static and dynamic inhomogeneous linewidth, and over 97% of its emission is in a broad, incoherent phonon side band, severely limiting scalability. Alternatively, the negatively charged SiV center exhibits excellent optical properties, with 70% of its emission in the zero phonon line and a narrow inhomogeneous linewidth. However, SiV− suffers from short electron spin coherence times, limited by an orbital relaxation rate (T1) of around 40 ns at 5 K.
Silicon is an attractive host for scalable quantum photonics, but the absence of bright telecom-band emitters with optically addressable spin states has limited its use for spin-photon interfaces. Here we demonstrate the Al1-center, an aluminum--carbon defect in silicon, as a bright waveguide-integrated single-photon emitter with a ground-state spin. Using isotopically purified silicon-on-insulator nanophotonic devices, we isolate individual Al1-centers and observe high-purity single-photon emission with g(2)(0)=0.04 without background subtraction. Time-resolved photoluminescence spectroscopy reveals a fast excited-state lifetime of 135 ns, nearly an order of magnitude shorter than the benchmark provided by the well-studied T-center. Resonant photoluminescence excitation measurements further resolve the zero-phonon transition and reveal a narrow homogeneous linewidth reaching 47 MHz, threefold narrower than the T-center under comparable temperature. Through magneto-optical spectroscopy, we resolve the spin-dependent transitions of the bound-exciton manifold and achieve spin-selective optical pumping, fulfilling the prerequisite for quantum state initialization and readout. These results establish the Al1-center as a bright telecom-band spin-photon interface in silicon photonics and introduce a promising platform for integrated quantum networks.