Journal Club 2013 | Tanabe Photonic Structure Group

Journal Club

By fiscal year (April-December)

Fiscal Year 2013

Presentation Details:

Quantum research based on the coupling of atoms and photons has been mostly studied by Cavity QED using optical resonators. In this study, we show that by appropriately arranging an atomic lattice around a nano-sized waveguide, a resonator in which the atomic lattice is regarded as a Bragg mirror can be fabricated on the waveguide and applied to Cavity QED and quantum information processing. Further application of this technology is expected to provide the basis for the construction of quantum information networks. In the presentation, we will explain the principle in detail.

Presentation Details:

Ultra-sensitive sensing technology enables us to observe and study many phenomena that could not be observed in the past. The Q-value of mechanical vibration has a significant influence on the sensitivity, and in this study, an extremely high Q-value was achieved by using optically trapped silica particles. Using the device, we have observed nonlinearities in thermal vibrations that could not be observed previously. The device is expected to achieve even higher sensitivity by using the Cooling technique.

Presentation Details:

The conventional spectroscopy using diffraction gratings has the problem of large size due to the necessity of spatially resolving wavelengths. However, if the Disordered-system, which has been the subject of much research in recent years, can be used instead of diffraction gratings, it is possible to realize a smaller spectrometer by using random scattering to increase the optical path length. In this paper, we report the realization of a small spectrometer on a chip by using disordered-photonic crystals.

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Photonic crystals are expected to be applied to optical circuits because of their compact size and high optical confinement. However, because of the difficulty of fabrication and the lack of clear design guidelines, this technology has not yet been realized. In this paper, we have realized 3D optical interconnection for the first time by using oblique waveguides.

Presentation Details:

One of the challenges in optical technology is the diffraction limit, which limits the miniaturization of optical elements to the wavelength scale. Surface plasmon polaritons, which utilize the coupling of electromagnetic waves and electrons, are one solution to this problem. Recently, research on plasmon lasers using this technology has been published, but one of these problems is the need for cooling down to about 10K. In this study, we fabricated a plasmon laser that can be operated at room temperature by using a resonator with a structure in which CdS and Ag are separated by MgF2. In this presentation, we will try to explain the results in an easy-to-understand manner for those who are not specialists in biology.

Presentation Details:

In research on quantum emitters, it is important to enhance the coupling between the emitter and the radiation mode, and we have been trying to enhance the interaction between light and matter by using resonators with high Q-values and plasmons with small mode volumes. In this study, we fabricated a plasmon resonator that can utilize both of these effects, and experimentally demonstrated the phenomenon of enhanced spontaneous emission from quantum dots and the ability to fabricate wavelength-selective single-photon sources from broadband quantum emitters. The presentation will include a discussion of the fundamentals of plasmons and other applied research.

Presentation Details:

Cell cycle analysis is of great importance in many cellular physiological processes and has gained increasing interest over the past few decades. In this context, technologies to analyze the cell cycle in real-time and spatiotemporally, such as Fucci technology, have attracted much attention, but label-free cell cycle analysis has not yet been achieved. This paper is the first study to analyze the cell cycle in a label-free manner without the use of fluorescent proteins, and its academic impact is significant. In this presentation, we aim to explain the results as clearly as possible to those who do not specialize in biology.

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However, the use of photonic crystals has made it possible to reduce the size of the device as well as to lower the threshold. However, by using photonic crystals, it was possible to reduce the size of the device and lower the threshold value.

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Quantum key distribution is a technology that is already in practical use. However, the transmission distance and secret key generation rate are limited due to the vulnerability of the existing BB84 protocol against eavesdropping and the low performance of APD-based single photon detectors. In this paper, we report on a differential phase-shift quantum key delivery protocol and a superconductor single-photon detector that achieves more than twice the transmission distance of conventional protocols. The presentation will focus on the differential phase shift protocol and the superconductor single-photon detector, and will emphasize the reasons why the longer transmission distance was achieved.

Presentation Details:

In optical resonators, the stability and sensitivity of the resonator depend on the accuracy of the mirrors at both ends. The influence of thermal noise is becoming increasingly important for use in optical atomic clocks and gravitational wave observation, and mirror coatings with higher stability than those of conventional mirrors are needed. To address this issue, the group fabricated a new single-crystal multilayer coating with low mechanical loss and high optical quality. A finesse of 150,000 was observed when a Fabry-Perot resonator was formed. Furthermore, we observed that the thermal noise was reduced to 1/10 of that of a conventional mirror at room temperature. This will enable the development of more sensitive resonators and more stable lasers. The presentation will focus on the experimental results of the fabricated mirrors.

Presentation Details:

Sensitive detection of temperature changes on the nanometer scale is a major challenge in modern science. A thermometer that has a temperature resolution of less than 1°C over a wide temperature range and can be integrated into living organisms would make a significant contribution, especially in the field of biology (e.g., regulation of gene expression and tumor metabolism by temperature). In this study, we propose a new nanometer-scale temperature measurement method based on the coherent manipulation of electron spins of the nitrogen vacancy color center (NV center) of diamond, including the demonstration of temperature measurement using the NV center and the results of in vivo experiments. The presentation will include the demonstration of temperature measurement using NV centers and the results of in vivo experiments. The presentation will focus on the experimental method and results.

Presentation Details:

Muneaki Hase, Masayuki Katsuragawa, Anca Monia Constantinescu & Hrvoje Petek Abstract: Optical nonlinearities in solid-state materials are very interesting because they can combine optical and electronic functions in high bandwidth information processing. Third-order nonlinear optical processes in silicon have been used for optical signal processing in the gigahertz band, but there have been no studies on optical modulation in the terahertz band. In this study, we have successfully generated a frequency comb with a bandwidth exceeding 100 THz at intervals of the fundamental frequency of longitudinal optical phonons (15.6 THz) by ultrafast modulation of the optical refractive index of silicon through the excitation of high-amplitude coherent longitudinal optical phonons by irradiating silicon with high-intensity femtosecond pulses.

Presentation Details:

Multiphoton absorption technology is expected to be applied to bio-imaging and three-dimensional optical recording. In this study, we report the first experimental observation of induced emission from a new phosphor by five-photon absorption. Compared to lower-order nonlinear absorption, the five-photon absorption process provides strong spatial confinement and very high imaging contrast. In addition, induced emission from two- to four-photon absorption has also been achieved under near-infrared laser excitation, and will be a promising multiphoton imaging probe with features such as no autofluorescence from the biological sample, deep penetration depth, and high sensitivity and resolution.

Presentation Details:

Research on light focusing beyond the diffraction limit of light has been active, and it has been found that evanescent light can be used to solve this problem. In recent years, there have been various techniques for controlling the focusing of near-field light, such as using small apertures, plasmonic crystals, and metamaterials, but all of them require the fabrication of fine and precise structures, and the degree of light focusing is structure-dependent. In contrast, this paper reports the discovery of a method that can arbitrarily control the degree of light focusing without requiring a fine structure.

Presentation Details:

The optical spin Hall effect, which is caused by the spin of a photon, has been observed for a long time, but it has not been easy to observe because the displacement with respect to the direction of the spin is small. In this paper, we succeeded in increasing the displacement by using a metamaterial with an array of gold antennas on the surface of a dielectric material, which facilitated the observation.

Presentation Details:

Negative-index metamaterials (NIMs) are expected to be applied to perfect lenses. However, conventional NIMs have high loss and do not have sufficient optical properties. In this paper, we report on the experimental realization of a three-dimensional NIM with low loss by using a fishnet-type structure. The presentation will focus on the history of NIM research and its principle.

Presentation Details:

The conversion of electrical signals to optical signals using nanophotonics will enable the integration of electronics and photonics. In this study, we succeeded in changing the resonance wavelength of the resonator by up to 2 nm and the resonator reflectivity by up to 400 % by using an L3 resonator in combination with graphene. Theoretical investigations have shown that the device has the potential to operate at 250 GHz with tens of fJ. The graphene resonator device is expected to enable faster electrical and optical conversion at lower power, despite its small size.

Presentation Details:

Mode-locked lasers are one of the methods to generate optical combs, but it is difficult to perform mode-locked operation in quantum cascade lasers because the gain recovery time is much shorter than the expected optical pulse propagation time for a single resonator cycle. However, it is difficult to perform mode-locking operation in a quantum cascade laser, because the gain recovery time is much shorter than the assumed optical pulse propagation time for one cavity cycle, resulting in the generation of another oscillation. In this study, an optical comb was generated by using a quantum cascade laser whose structure was designed to have flat group velocity dispersion, using FWM instead of mode-locking. This is expected to be a broadband, compact, and current-injection-driven optical comb source in the mid-infrared region.

Presentation Details:

There are two main approaches to printing at the diffraction limit (250 nm): inkjet and laserjet methods, and surface plasmons, which will be used in this study. The inkjet method has excellent resolution, but can only produce monochrome images. On the other hand, the nanohole filter using surface plasmons requires a periodic structure, resulting in microscale resolution. In this report, we succeeded in coloring the nanostructures without periodic dependence by inserting a reflective film under the nanostructures, and achieved diffraction-limited resolution using surface plasmons. The coloring was achieved by controlling the interaction between surface plasmon and Fano resonance by changing the shape of the nanostructure. In the presentation, I will give a wide-ranging explanation, including reports on plasmonics research at CLEO-PR & OECC/PS.

Presentation Details:

It has been mathematically proven that multilayers with a staircase-like refractive index distribution exhibit antireflection properties over a wide bandwidth. However, the absence of low refractive index materials with a refractive index very close to that of air has prevented the realization of broadband antireflective coatings. In this study, thin films of TiO2 and SiO2 were prepared by oblique deposition and their refractive indices were adjusted to eliminate Fresnel reflection over a wide bandwidth. A minimum refractive index of n = 1.05 was achieved in the SiO2 film.

Presentation Details:

Mitsuru Saito, Kouji Taniguchi, and Taka-hisa Arima Abstract: Despite the recent discovery of multiferroic materials, the maximum directional dichroism of these materials is 0.1%. In this study, we succeeded in obtaining a very large directional dichroism of 100% by using a material with a relatively small degree of temporal objectivity and spatial symmetry breaking, which are the conditions for being a multiferroic material. This is due to the large coupling between the electric and magnetic dipole transitions. In the presentation, we will give a detailed explanation starting from the basic subject of the electro-magnetic effect.

Presentation Details:

Absorption imaging has been applied in a wide variety of fields, starting from the discovery of red blood cells to the observation of dust clouds in stars and Bose-Einstein condensation in modern times. In this paper, a single atom isolated in a vacuum is trapped by RF Paul trapping and imaged with wavelength resolution using a phase Fresnel lens. This is the first imaging by absorption in the world. Since the optical properties of atoms are well understood, atoms are ideal samples for understanding the limits of absorption imaging. This result will provide a new method for imaging light-sensitive samples in the visible and X-ray regions.

Presentation Details:

For quantum information processing, it is important to form a quantum network that connects each quantum system. However, the formation of quantum nodes in the network has been a major challenge. In this study, we formed a node by supplementing rubidium atoms in an optical resonator, and succeeded in the communication of quantum states of atoms and the formation of entanglement between two remote quantum systems. In this Journal Club presentation, we will focus on the demonstration of entanglement in two isolated quantum systems.

Presentation Details:

By arranging gold antennas on a dielectric surface, it is possible to transmit or reflect an incident plane wave in any direction by changing the phase on the surface. Since a simple dipole cannot achieve a phase change of 360°, we proposed a "V-antenna" and optimized the length of the edges and the angles between them to achieve a wide range of phase change while maintaining the scattering intensity. Furthermore, by applying the phase change point-symmetrically to the center, the generation of a Laguerre-Gaussian beam was also confirmed.

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What is Journal Club?
This is an open lecture series held in Tanabe Photonic Structures Laboratory. Students who are graduate students or above will survey papers related to optics and related technologies such as photonics, materials, bioscience, etc., and explain them in an easy-to-understand manner.

About auditing
Attendance is free, regardless of whether you are inside or outside of the university. The seminar will be held periodically, so if you are interested in any of the topics, please feel free to attend. No notice is required to attend, but we will prepare materials if you contact us in advance.

Announcement of the event
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