Publications

@article{takada_chiral,

title = {Sensitivity improvement of a single-NV diamond magnetometer using a chiral waveguide},

author = {Kosuke Takada and Ryota Katsumi and Takashi Yatsui},

doi = {10.1364/OE.509860},

year  = {2024},

date = {2024-01-01},

urldate = {2024-01-01},

journal = {Optics Express},

volume = {32},

issue = {1},

pages = {795-802},

abstract = {A single nitrogen-vacancy (NV) center in diamond is utilized to perform nanoscale magnetic measurements. However, the low contrast and poor collection efficiency of spin-dependent emitted photons limited the instrument sensitivity to approximately several nT/√Hz. Here, we design a diamond magnetometer based on a chiral waveguide. We numerically demonstrate that the proposed device achieves a sensitivity of 170 pT/√Hz owing to near-unity contrast and efficient photon collection. We also confirm that the device sensitivity is robust against position misalignment and dipole misorientation of an NV center. The proposed approach will enable the construction of a highly-sensitive magnetometer with high spatial resolution.},

keywords = {Diamond},

pubstate = {published},

tppubtype = {article}

}

@article{katsumi23flip,

title = {Hybrid integration of ensemble nitrogen-vacancy centers in single-crystal diamond based on pick-flip-and-place transfer printing },

author = {Ryota Katsumi and Kosuke Takada and Shun Naruse and Kenta Kawai and Daichi Sato and Takeshi Hizawa and Takashi Yatsui},

doi = {10.1063/5.0161268},

year  = {2023},

date = {2023-09-13},

urldate = {2023-09-13},

journal = {Applied Physics Letters},

volume = {123},

issue = {11},

pages = {111108},

abstract = {Incorporating color centers in diamond with mature integrated photonics using hybrid integration techniques such as transfer printing provides a promising route toward scalable quantum applications. However, single-crystal diamond nanostructures fabricated using current etching technologies have triangular bottoms that are unsuitable for conventional pick-and-place integration. Herein, we present an alternative approach for deterministically integrating diamond nanostructures on chip. We demonstrate the hybrid integration of a diamond triangular nanobeam containing a nitrogen-vacancy ensemble on an SiO2 chip by picking it up using a weak adhesive film, flipping it, and transferring it to a stronger one. This “pick-flip-and-place” approach provides a flat diamond-chip interface, enabling the high-yield hybrid integration regardless of the shape of diamond nanostructures. Additionally, diamond nanofabrication is facilitated by transfer-printing hard masks for diamond etching. We also show that the integrated diamond nanobeam functions as a nanoscale quantum sensor. Our proposed approach paves the way toward scalable hybrid-diamond quantum photonics.},

keywords = {Diamond, NV center},

pubstate = {published},

tppubtype = {article}

}

@article{katsumi_grating,

title = {Transfer-printing-based integration of silicon nitride grating structure on single-crystal diamond toward sensitive magnetometers},

author = {Ryota Katsumi and Takeshi Hizawa and Akihiro Kuwahata and Shun Naruse and Yuji Hatano and Takayuki Iwasaki and Mutsuko Hatano and Fedor Jelezko and Shinobu Onoda and Takeshi Ohshima and Masaki Sekino and Takashi Yatsui},

doi = {10.1063/5.0107854},

year  = {2022},

date = {2022-10-19},

urldate = {2022-10-19},

journal = {Applied Physics Letters},

volume = {121},

issue = {16},

pages = {161103},

abstract = {Negatively charged nitrogen-vacancy (NV) centers in diamond have emerged as promising candidates for a wide range of quantum applications, especially quantum sensing of magnetic field. Implementation of nanostructure into diamond is powerful for efficient photon collection of NV centers and chip-scale miniaturization of the device, which is crucial for sensitive and practical diamond magnetometers. However, fabrication of the diamond nanostructure involves technical limitations and can degrade the spin coherence of the NV centers. In this study, we demonstrate the hybrid integration of a silicon nitride grating structure on a single-crystal diamond by utilizing transfer printing. This approach allows the implementation of the nanostructure in diamond using a simple pick-and-place assembly, facilitating diamond-based quantum applications without any complicated diamond nanofabrication. We observed the intensity enhancement in the collected NV emissions both theoretically and experimentally using the integrated grating structure. By applying the increased photon intensity, we demonstrate the improved magnetic sensitivity of the fabricated device. The proposed hybrid integration approach will offer a promising route toward a compact and sensitive diamond NV-based magnetometer.},

keywords = {Diamond, magnetometer},

pubstate = {published},

tppubtype = {article}

}

@article{katsumi22sensor,

title = {Design of an ultra-sensitive and miniaturized diamond NV magnetometer based on a nanocavity structure},

author = {Ryota Katsumi and Masaki Sekino and Takashi Yatsui},

doi = {10.35848/1347-4065/ac7e10},

year  = {2022},

date = {2022-07-05},

urldate = {2022-07-05},

journal = {Japanese Journal of Applied Physics},

volume = {61},

number = {8},

pages = {082004},

abstract = {Ensembles of nitrogen-vacancy (NV) centers in diamond allow for the potential realization of sensitive magnetometers by leveraging their excellent spin properties. However, NV-based magnetometers are limited by their experimental magnetic field sensitivity owing to inefficient photon collection. Moreover, they are disadvantageous for reduced spatial resolution and excessive excitation power. To overcome these issues, we propose ultra-sensitive diamond magnetometers based on nanocavities. The device structure can attain high collection efficiencies and enhance the photon emission intensity of the NV ensemble. This device can allow the efficient photon collection even when considering the positional distribution of the NV centers. Our theoretical analysis indicated that the minimum expected sensitivity is 60 fT/√Hz. Proposed design can achieve volume-normalized sensitivity of 0.92 aT/√(Hz/cm3) along with a required power of 7 μW, both of which are superior to those of bulk diamond. The proposed approach offers a promising route toward highly sensitive and energy-efficient magnetometers.},

keywords = {Diamond},

pubstate = {published},

tppubtype = {article}

}

@article{Kuwahata2020,

title = {Magnetometer with nitrogen-vacancy center in a bulk diamond for detecting magnetic nanoparticles in biomedical applications},

author = {Akihiro Kuwahata and Takahiro Kitaizumi and Kota Saichi and Takumi Sato and Ryuji Igarashi and Takeshi Ohshima and Yuta Masuyama and Takayuki Iwasaki and Mutsuko Hatano and Fedor Jelezko and Moriaki Kusakabe and Takashi Yatsui and Masaki Sekino},

url = {https://www.altmetric.com/details/75906559},

doi = {10.1038/s41598-020-59064-6},

year  = {2020},

date = {2020-02-01},

journal = {Scientific Reports},

volume = {10},

pages = {2483},

publisher = {Springer Nature},

abstract = {We developed a novel magnetometer that employs negatively charged nitrogen-vacancy (NV−) centers in diamond, to detect the magnetic field generated by magnetic nanoparticles (MNPs) for biomedical applications. The compact probe system is integrated into a fiber-optics platform allowing for a compact design. To detect signals from the MNPs effectively, we demonstrated, for the first time, the application of an alternating current (AC) magnetic field generated by the excitation coil of several hundred microteslas for the magnetization of MNPs in diamond quantum sensing. In the lock-in detection system, the minimum detectable AC magnetic field (at a frequency of 1.025 kHz) was approximately 57.6 nT for one second measurement time. We were able to detect the micromolar concentration of MNPs at distances of a few millimeters. These results indicate that the magnetometer with the NV− centers can detect the tiny amounts of MNPs, thereby offering potential for future biomedical applications.},

keywords = {Diamond, NV center},

pubstate = {published},

tppubtype = {article}

}

@article{2018Felix,

title = {Improving the electron spin properties of nitrogen-vacancy centres in nanodiamonds by near-field etching},

author = {Felix Brandenburg and Ryosuke Nagumo and Kota Saichi and Kosuke Tahara and Takayuki Iwasaki and Mutsuko Hatano and Fedor Jelezko and Ryuji Igarashi and Takashi Yatsui},

doi = {10.1038/s41598-018-34158-4},

year  = {2018},

date = {2018-10-01},

urldate = {2018-10-01},

journal = {Scientific Reports},

volume = {8},

pages = {15847},

publisher = {Springer Nature},

abstract = {The nitrogen-vacancy (NV) centre in diamond is a promising candidate for quantum computing applications and magnetic sensing applications, because it is an atomic-scale defect with stable coherence time (T2) and reliable accessibility at room temperature. We demonstrated a method for improving the NV spin properties (the full width half maximum (FWHM) value of the magnetic resonance spectrum and T2) through a near-field (NF) etching method under ambient conditions. The NF etching method, based on a He-Cd ultraviolet laser (325 nm), which is longer than the absorption edge of the oxygen molecule, enabled selective removal of defects on the nanodiamond surface. We observed a decrease in the FWHM value close to 15% and an increase in T2 close to 25%. Since our technique can be easily reproduced, a wide range of NV centre applications could be improved, especially magnetic sensing applications. Our results are especially attractive, because they have been obtained under ambient conditions and only require a light source with wavelength slightly above the O2 absorption edge.},

keywords = {Diamond, Nanophotonic fabrication, Near-field etching, NV center},

pubstate = {published},

tppubtype = {article}

}

@article{2015NagumoAPA,

title = {Spectral control of nanodiamond using dressed photon-phonon etching},

author = {Ryosuke Nagumo and Felix Brandenburg and Anna Ermakova and Fedor Jelezko and Takashi Yatsui},

doi = {10.1007/s00339-015-9400-0},

year  = {2015},

date = {2015-12-01},

journal = {Applied Physics A},

volume = {121},

number = {4},

pages = {1335-1339},

publisher = {Springer Nature},

abstract = {The luminescence of a nitrogen-vacancy (NV) center in a nanodiamond (ND) is of great interest because of its features, especially in the field of nanophotonics. When an NV center in an ND is located in the vicinity of the surface, the emission is often disturbed by any surface defects, resulting in non-radiative recombination. In this work, we performed dressed photon-phonon (DPP) etching of the NDs, and found that the size of the NDs decreased, while the cathodoluminescence (CL) intensity increased. We assume that this increase in the CL intensity originates from the removal of the surface protrusions and/or defects by DPP etching.},

keywords = {Diamond, Nanophotonic fabrication, Near-field etching, NV center},

pubstate = {published},

tppubtype = {article}

}

@article{doi:10.1002/pssa.201431161,

title = {Polarization-controlled dressed-photon–phonon etching of patterned diamond structures},

author = {Takashi Yatsui and Daisuke Takeuchi and Satoshi Koizumi and Kazuki Sato and Kohei Tsuzuki and Takayuki Iwasaki and Mutsuko Hatano and Toshiharu Makino and Masahiko Ogura and Hiromitsu Kato and Hideyo Okushi and Satoshi Yamasaki},

doi = {10.1002/pssa.201431161},

year  = {2014},

date = {2014-10-01},

journal = {physica status solidi (a)},

volume = {211},

number = {10},

pages = {2339-2342},

abstract = {To realize an ultra-flat diamond surface with a three-dimensional (3D) structure, we performed dressed-photon–phonon (DPP) etching. A DPP is generated on nano-scale protrusions. Hence, the generation of DPPs results in selective removal of nano-scale protrusions, thereby achieving an ultra-flat surface even on the sidewall of a diamond mesa structure. By controlling the polarization of the incident light, a smooth diamond mesa structure sidewall was obtained, and a higher etching rate was obtained with a perpendicular polarization on the corrugations. In addition, by selective deposition of n-layer diamond on the p-layer diamond mesa structure, smooth n-layer diamond was confirmed on the DPP etched sidewall. Schematic of dressed-photon–phonon (DPP) etching on the sidewall: (a) before and (b) after etching, in which DPP selectively generates on the corrugations and etching automatically stops when the surface was smooth. Scanning electron microscopy image of the selective deposition of the n-layer (c) without and (d) with the DPP etched sidewall.},

keywords = {Diamond, First, Nanophotonic fabrication, Near-field etching},

pubstate = {published},

tppubtype = {article}

}

@article{Yatsui_2012,

title = {Realization of an atomically flat surface of diamond using dressed photon–phonon etching},

author = {Takashi Yatsui and Wataru Nomura and Makoto Naruse and Motoichi Ohtsu},

url = {https://doi.org/10.1088%2F0022-3727%2F45%2F47%2F475302},

doi = {10.1088/0022-3727/45/47/475302},

year  = {2012},

date = {2012-11-01},

journal = {Journal of Physics D: Applied Physics},

volume = {45},

number = {47},

pages = {475302},

publisher = {IOP Publishing},

abstract = {We obtained an atomically flat diamond surface following dressed photon–phonon (DPP) etching using 3.81 eV light and O2 gas. We obtained a surface roughness (Ra) of 0.154 nm for Ib-type (1 1 1) diamond and 0.096 nm for Ib-type (1 0 0) diamond. To evaluate the surface roughness, we grouped the surface into bins of width l and introduced the standard deviation of the height difference function for a given separation l, which allowed us to determine the height variation of the surface. Based on the calculation of standard deviation, the conventional adiabatic photochemical reaction did not remove the small surface features, while DPP etching decreased the surface roughness for all length scales.},

keywords = {Diamond, First, Nanophotonic fabrication, Near-field etching},

pubstate = {published},

tppubtype = {article}

}