Publications

@article{kitaizumi20,

title = {Magnetic field generation system of the magnetic probe with diamond quantum sensor and ferromagnetic materials for the detection of sentinel lymph nodes with magnetic nanoparticles},

author = {Takahiro Kitaizumi and Akihiro Kuwahata 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},

doi = {10.1109/TMAG.2020.3009334},

year  = {2021},

date = {2021-01-21},

journal = {IEEE Transactions on Magnetics},

volume = {57},

number = {2},

pages = {5100405},

abstract = {We have developed the magnetic probe with a diamond quantum sensor and electromagnetic coils to detect sentinel lymph nodes (SLNs), as the medical application of diamond quantum sensing. The probe magnetizes magnetic nanoparticles (MNPs) accumulated in SLNs and detect the magnetic fields of magnetized MNPs. In this study. We designed a ferromagnetic core that has a unique shape and optimized the magnetic field generation system for improving the detection performance, such as the magnetic sensitivity and detectable distance. The proposed magnetic core enhances an excitation magnetic field strength at a longer distance and suppresses a bias field strength at a location of the diamond quantum sensor. The increment of the excitation field is approximately 370% and the decrement of the bias field is approximately 45%. In addition to the proposed magnetic core, even applying a cancellation coil, the excitation field strength is ten-fold compared with the coil only structure, suggesting the larger magnetization of MNPs generates the large magnetic field for longer detectable distance.},

keywords = {NV center},

pubstate = {published},

tppubtype = {article}

}

@article{amp20,

title = {Amplification by stimulated emission of nitrogen-vacancy centres in a diamond-loaded fibre cavity},

author = {Sarath Raman Nair and Lachlan J. Rogers and Xavier Vidal and Reece P. Roberts and Hiroshi Abe and Takeshi Ohshima and Takashi Yatsui and Andrew D. Greentree and Jan Jeske and Thomas Volz},

doi = {10.1515/nanoph-2020-0305},

year  = {2020},

date = {2020-11-01},

urldate = {2020-11-01},

journal = {Nanophotonics},

volume = {9},

number = {15},

pages = {4505-4518},

abstract = {Laser threshold magnetometry using the negatively charged nitrogen-vacancy (NV−) centre in diamond as a gain medium has been proposed as a technique to dramatically enhance the sensitivity of room-temperature magnetometry. We experimentally explore a diamond-loaded open tunable fibre-cavity system as a potential contender for the realisation of lasing with NV− centres. We observe amplification of the transmission of a cavity-resonant seed laser at 721 nm when the cavity is pumped at 532 nm and attribute this to stimulated emission. Changes in the intensity of spontaneously emitted photons accompany the amplification, and a qualitative model including stimulated emission and ionisation dynamics of the NV− centre captures the dynamics in the experiment very well. These results highlight important considerations in the realisation of an NV− laser in diamond.},

keywords = {Near-field etching, NV center},

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}

}