We report on use of coverslip-based microwave antenna as an experimental platform for quantitatively characterizing NV spin properties of different types of fluorescent nanodiamonds (NDs). This coverslip antenna provides as-designed magnetic field of microwaves for spin excitation, thereby precisely determining NV spin relaxation times (T1, T2) of conventional type-Ib NDs and 12C-enriched NDs. Furthermore, we demonstrate measurements of the spin relaxation times inside live cells (HeLa and HepG2). We discuss potential applications of 12C enriched nanodiamonds for biologicals sensing with our coverslip antenna devices.
Optical condensation is a method for the rapidly and densely assembling dispersoids on the substrate. Recently, we developed the metallic nanofilm-coated optical fiber (MNOF) module to perform optical condensation on the three-dimensionally arbitrary position in dispersion liquid although the convection profile was limited in the case of a two-dimensional photothermal source. In this work, we investigate the effect of interface on the optical condensation using MNOF by changing the position from the substrate. Remarkably, the assembly efficiency of optical condensation with MNOF can be 1 to 2 orders of magnitude higher than that of conventional optical condensation two-dimensional case. These results will lead to a high-performance analysis of various small objects, such as microbes and biomaterials.
We report a notch-shaped coplanar microwave waveguide antenna on a glass plate designed for on-chip detection of optically detected magnetic resonance (ODMR) of fluorescent nanodiamonds (NDs). A lithographically patterned thin wire at the center of the notch area in the coplanar waveguide realizes a millimeter-scale ODMR detection area (1.5 × 2.0 mm^2) and gigahertz-broadband characteristics with low reflection (∼8%). The ODMR signal intensity in the detection area is quantitatively predictable by numerical simulation. Using this chip device, we demonstrate a uniform ODMR signal intensity over the detection area for cells, tissue, and worms.
Real-time temperature monitoring inside living organisms provides a direct measure of their biological activities, such as homeostatic thermoregulation and energy metabolism. Here, using quantum nanothermometers based on optically accessible electron spins of nitrogen vacancy centers in nanodiamonds, we demonstrate in vivo real-time temperature monitoring inside nematode worms. We developed a thermometry system that can measure the temperatures of mobile nanodiamonds inside the worms with a precision of ± 0.22 oC. Using this system, we determined the increase in temperature based on the thermogenic responses of the worms during the chemical stimuli of mitochondrial uncouplers.
Chemical reactions occurring in biological processes are either endergonic or exergonic, which exchange heat between the system and surrounding. Detecting thermogenic responses with high sensitivity is of fundamental importance to characterize and diagnose the biological systems. In regenerative medicine, the culture temperature and the thermogenic properties of stem-cells significantly affect the subsequent growth of regenerative cells and tissues, thereby preventing efficient growth of regenerative organs from stem cells. However, such thermogenic analyses at single cellular level have been elusive until now.
Here we demonstrate microscope-based thermometry of adipose-tissue derived stem cells (ASCs [1]) taken from mice by using quantum sensors based on the electron spin resonance of color defect centers in fluorescent nanodiamonds (FNDs) [2]. ASCs are successfully labeled with FNDs while keeping the original ability for the proliferation and differentiation to osteocytes and adipocytes. The FND-labeled ASCs are measured to detect the intracellular temperature change. The FNDs act as nanoparticle thermometers in ASCs with the temperature dependence of - 63 kHz/oC with temperature accuracy of ± 0.9 oC and precision of ± 0.5 oC [3]. The present demonstration makes a new direction of the quantum sensor applications toward stem-cell research and regenerative medicine.
[1] Yukawa et al., Adv. Drug Deliv. Rev. 95 , 2 (2015).
[2] Fujiwara et al., Nanotech. 27, 455202 (2016): arXiv:1803.06179. (2018).
[3] Manuscript in preparation.
We demonstrate successful cooling of ultrathin fiber tapers and their coupling with nitrogen vacancy (NV) centers in nanodiamonds at cryogenic temperatures. Nanodiamonds containing multiple NV centers are deposited on ultrathin fiber tapers with diameters ranging from 450-500 nm. The fiber tapers were successfully cooled down to 9 K with our special fiber mount and an optimization of cooling speed. The fluorescence coupled with the fiber tapers showed characteristic sharp zero-phonon lines of neutral and negatively charged NV centers. The present demonstration is important for the future NV-based quantum information devices and sensitive nanoscale cryogenic magnetometry.
KEYWORDS: Single photon, Luminescence, Near field, Fiber couplers, Nitrogen, Optical filters, Quantum information, Fiber lasers, Confocal microscopy, Near field optics
Further miniaturization of funcionalized quantum optical systems down to nm-dimensions and their integration
into fibre optical networks is a major challange for future implementations of quantum information, quantum
communication and quantum processing applications. Furthermore, scalability, long-term stability and room- as
well as liquid helium temperature operation are benchmarking properties of such systems.
In this paper, we present the realizations of fiber-coupled diamond-based single photon systems. First, an
alignment free, μm-scale single photon source consisting of a single nitrogen vacancy center facet coupled to
an optical fiber operating at room temperature is presented. Near-field coupling of the single nitrogen vacancy
center is realized by placing a pre-selected nanodiamond directly on the fiber facet in a bottom-up approach.
Its photon collection efficiency is comparable to a far-field collection via an air objective with a numerical
aperture of 0.82. As the system can be simultaneously excited and its photons be recollected through the
fiber, it can be used as a fiber-connected single quantum sensor that allows optical near-field probing on the
quantum level. Secondly single nanodiamonds that contain nitrogen vacancy defect centers, are near-field coupled
to a tapered fiber of 300 nanometer in diameter. This system provides a record-high number of 97 kcps single
photons from a single defect center into a single mode optical fiber. The entire system can be cooled to liquid
Helium temperatures and reheated without breaking. Furthermore, the system can be evanescently coupled to
various nanophotonic structures, e.g. microresonators. The system can also be applied for integrated quantum
transmission experiments and the realization of two-photon interference. It can be used as a quantum-randomnumber
generator as well as a probe for nano-magnetometry.
We report the substrate effects on the zero-phonon transitions and suppression of phonon side bands in the NV center
spectrum. Fluorescence spectra of NV centers in cryogenic temperatures were measured by depositing diamond
nanocrystals on different substrates including glass slides, undoped Si, and silica (1~2μm) on undoped Si (SiO2/Si). We
found that SiO2/Si substrate was an effective substrate to suppress the phonon side band from spectra of NV- centers.
Temperature dependence of NV- zero-phonon line Debye-Waller factor on Si and SiO2/Si were measured, from 2.5K to
230K, Debye-Waller factor decreased linearly on both of the two substrates.
An ultrahigh-Q optical microcavity coupled with a tapered fiber is an ideal system for the cavity quantum
electrodynamics (CQED). In particular realizing this system at cryogenic temperature is vitally important and has been
recently explored for various CQED applications including solid-state atom-photon strong coupling, vibrational mode
cooling, and photonic quantum gates. These cryogenic fiber-coupled microcavity systems, however, suffer from
mechanical vibrations due to cooling systems and distortions caused by large temperature change. These factors may
cause the degradation in polarization of probe light field in the system. Here we report the analysis of the polarization
state in a tapered-fiber-coupled microsphere cavity at cryogenic temperatures. By scanning the wavelength of the probe
light at around 637 nm, which can be used for the diamond nitrogen vacancy centers, the spectral analysis of the
polarization state was performed at 8-30 K. We have found that the degree of polarization (DOP, classical analogue of
purity) at cryogenic temperatures does not show significant change compared to that measured at room temperature. This
fact indicates that the system can conserve the polarization at low temperature to the extent comparable to that at room
temperature, which is enough for the evaluation of the quantum phase gate.
Widely tunable terahertz (THz) -wave generation using difference frequency generation (DFG) in an organic N-Benzyl-2-methyl-4-nitroaniline (BNA) crystal was demonstrated. An organic nonlinear optical (NLO) BNA crystal is one of the
promising materials for efficient and strong THz-wave generation because of its potential to have a sufficiently large
enough second-order optical nonlinearity. Large and high quality single crystals of BNA (Φ8×30mm) were successfully
grown by a vertical Bridgman method. The NLO coefficient d33 of BNA crystal is about 230pm/V. It is the largest value reported for any yellow-colored NLO materials. BNA has low refractive index dispersion between the optical and THz-wave
region, therefore the colinear phase matching condition of the Type0 configuration is satisfied by using 0.7~1μm
band pump wavelength. So, we developed a near-infrared dual-wavelength pump source for BNA-DFG. Two KTiOPO4
(KTP) crystals were mounted on galvano scanners inside a double-pass optical parametric oscillator (OPO). It is pumped using a frequency-doubled Nd:YAG laser (532 nm, 8 ns, 100 Hz). The signal wave of the KTP-OPO output was controlled independently and rapidly using a galvano scanner. We successfully generated THz-wave using organic BNA
crystal. The THz-wave generation range is from 0.1 to 15THz, while the pumping dual-wavelength is controlled in the 0.8-0.9μm range.
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