Journal Club 2014 | Tanabe Photonic Structure Group

Journal Club

By fiscal year (April-December)

Fiscal Year 2014

Presentation Details:

The demand for highly integrated devices and low power consumption has led to the need for nanoscale electronic components. In this study, an atomic switch was formed by forming an atomic-size aluminum contact at the neck of an aluminum wire. This is based on the change in electrical conductivity caused by a change in the position of atoms, called electromigration, which occurs when an electric current is applied to the contact. In this research, the bistability of the electrical conductivity is also used for memory applications.

Presentation Details:

The role of gas molecules in the metabolism of living organisms is still unknown in many respects. This is due to the nature of gases themselves and the difficulty of their measurement. Raman scattering is often used to detect gas molecules, but the intensity of Raman scattering light is weak and difficult to detect. In this paper, we report a new device for measuring and mapping Raman spectra of mouse brain slices using Serface Enhanced Raman Scattering (SERS), which is a simple and inexpensive method.

Presentation Details:

Recently, optomechanics based on optical radiation pressure has been studied, but its operation is considered to be very small (a few nm) and not suitable for applications. In this paper, we fabricated a "photon see-saw" structure and successfully coupled two resonators and exchanged photons by using optomechanical rotation.

Presentation Details:

Developing a stable single-photon source is an important issue in quantum communications. Quantum dots are a solution to this problem. The stability of single-photon generation is strongly dependent on the laser intensity, since Rabi oscillations occur in the number of single-photon generation due to changes in the pulse area. In this study, we have confirmed that single photons are generated stably by using the Adiabatic Rapid Passage technique, in which a positive chirp is applied to the incident pulse, and that single photons with identical characteristics are generated continuously with a probability of 99.5% by the Hong Ou Mandel The results were confirmed by the Hong Ou Mandel interference.

Presentation Details:

Cavity QED is a well-known concept in quantum communication that can be used as a single-photon source or to exchange quantum states with light. atoms in a Cavity QED always have Rabi oscillations, which constantly move between the excited level and the reference level. It is believed that the communication of quantum information can be controlled by controlling these oscillations. However, while this control has been achieved in the microwave regime, it has not been achieved in the optical frequency regime. This paper describes how this has been achieved using photonic crystals and the Stark shift effect.

Presentation Details:

In quantum mechanics, the ability to identify superposition states determines whether or not quantum interference occurs. In addition, by observing one of the entangled states, it is possible to know the state of the other. In this paper, we present the concept of quantum imaging that takes advantage of these two interesting properties. Specifically, it is a system that enables imaging of an object without detecting the light itself that interacts with the object to be detected. This is expected to expand the choice of detectors and light sources. In addition, this method has the advantage over other methods of quantum imaging that it does not require coincidence measurements.

Presentation Details:

Metamaterials are expected to be applied to cloaking technology and hyperlenses. However, it has been considered difficult to fabricate metamaterials that require materials that rarely exist in nature, such as those with a high refractive index, because their behavior is determined by the materials that make up the metamaterials and the way they are arranged. In this paper, we show that it is possible to create metamaterial bytes with any dielectric constant by combining only two materials called metamaterial bits, and to fabricate hyperlenses and other devices by arranging them appropriately.

Presentation Details:

Fabricating photonic devices on thin, soft plastic substrates is useful for applications such as sensors that can be utilized on the surface of human skin, but conventional fabrication methods are difficult to integrate in complex ways and have limited capacity. In this study, the authors fabricated a single soft photonic device using chalcogenide glass with high refractive index contrast. The development of such technology is expected to be applied to various photonic devices. In this presentation, several experiments using this technique will be presented.

Presentation Details:

Although metamaterial metamaterial lenses made of gold have already been studied, in this study, we designed and fabricated an ultrathin film lens using only silicon, which has advantages in terms of process simplicity and economic efficiency. Normally, wavefronts are formed by spatially modulating the phase from 0 to 2π, but in this study, the lens is designed by combining modulation from 0 to π and circular polarization. In the presentation, we will also introduce other research on ultra-thin film lenses fabricated on silicon base.

Presentation Details:

Although photons are neutral particles that do not interact directly with magnetic fields, recent theoretical studies have shown that an effective magnetic field can exist when the phase of the light changes with the direction of propagation. In this study, the effect of this effective magnetic field was experimentally observed using a silicon-based Ramsey-type interferometer. An effective magnetic flux from 0 to 2π corresponding to a non-reciprocal 2π phase shift with an interference fringe extinction ratio of 2.4 dB was obtained at an interferometer length of 8.35 mm, which is comparable to that obtained in monolithic integrated devices using common magnetooptic materials. In the presentation, the theoretical study on the effective magnetic field by S. Fan et al. will also be discussed.

Presentation Details:

Terahertz light is expected to be used for sensing and wireless communication, but the size of the devices used for detection is a problem. However, the size of the devices used for detection is a problem. In this paper, we propose a new method to detect a wide frequency range in small devices using photonic crystals with several structural modifications.

Presentation Details:

In recent years, research on information communication using light has progressed, and optical signal memory using micro optical resonators and EITs has attracted much attention. In this study, we demonstrated that it is possible to generate differences in the mechanical state of the device structure by controlling the light incident on the device, and by actually identifying and storing signals based on these differences in state, we improved the signal storage time and room-temperature operation.

Presentation Details:

Optical detection of small units such as molecules or atoms has been demonstrated under cryogenic temperature by means of Raman scattering, absorption, However, whatis already detected is the ensemble signals of single molecules, which rapldly decays in order of pico-second due to the decoherence of emitted signals. Hence, the truly meaning of "Single" molecule vibration detection is first reported in this paper. The talk will be held in English this time for personal reasons.

Presentation Details:

In recent years, there has been an increase in the volume of data communications, such as video downloading, and greater communication capacity is desired. In optical communications, various multiplexing methods such as wavelength division multiplexing, time division multiplexing, and polarization division multiplexing have been considered in order to increase the communication capacity. In this study, orbital angular frequency is used as an additional element that can be added to these multiplexing methods, and multiplexing it together with polarization achieves high-capacity communications on the order of terabits.

Presentation Details:

Up-conversion nanoparticles can convert infrared light into visible light and are expected to be used in solar cells and ecological imaging. To function as up-conversion nanoparticles, they must be doped with a sensitizer that absorbs infrared light and an activator that emits visible light. The intensity of the visible light emitted depends on the amount of the activator, and previous studies have shown that there is an optimal amount of the activator. In other words, it is generally accepted that the intensity of visible light emitted from nanoparticles is inherently limited. In this paper, we investigate a method to overcome this limitation and succeed in emitting visible light that is 70 times stronger than the emission intensity considered to be the highest intensity in the past.

Presentation Details:

Using a CO2 laser, we succeeded in welding a toroidal micro optical resonator to a tapered fiber and achieved a Q-value of 3.21×10^5. Furthermore, optical measurements of the toroidal micro optical resonator were performed using a three-dimensional microchannel created with a femtosecond laser, and the refractive index, which changes with the concentration of salt water, was successfully measured on the order of 10^-4. The key point of this experiment was the packaging of a toroidal micro optical resonator with a high Q value and a three-dimensional microfluidic channel.

Presentation Details:

For the first time, 10 Gb/s optical modulation was achieved using photonic crystal waveguides with embedded pn junctions. The photonic crystal waveguides are fabricated using a CMOS-compatible process and covered with a silica cladding. Optical modulation was performed using non-return-to-zero electrical signals, and good eye patterns were observed at modulation rates of 10 Gb/s and 2 Gb/s, respectively. In the presentation, we will also introduce related research on photonic crystal resonators using slow light and CMOS-compatible processes.

Presentation Details:

Quantum key distribution using single photons has been proposed as an absolutely secure communication method, but one of the problems in realizing quantum communication networks is that each receiver (detector) needs to be highly accurate. In this study, we proposed a one-to-many network in which there are multiple senders for each receiver, and conducted experiments to investigate the feasibility of this network. Since only one receiver is used, the network can be easily constructed, and this is expected to make quantum communication more accessible.

Presentation Details:

In recent years, many remarkable research results have been reported in the field of devices with random media and structures, such as random lasers. Although random devices have multiple and random modes of light, it has been shown that it is theoretically possible to select a certain mode of light. In this study, we actually fabricated such devices and verified the results. We are also examining the phenomena that occur when the device is post-processed. The presentation will focus on the experimental results.

Presentation Details:

In recent years, many remarkable results have been reported in the field of the combination of atoms and optical devices such as Cavity QED. In this study, we propose a new photonic crystal waveguide with a special shape called an alligator photonic crystal waveguide (APCW). APCWs are characterized by their ability to catch and manipulate atoms in the vicinity of the waveguide. The future prospect of this APCW is that it will be possible to construct a system that mixes atoms and photons integrated on the same chip. The detailed principle of APCW will be explained in the presentation.

Presentation Details:

In the development of spacecraft, solar sails, which are propelled by the light pressure of the sun, are being developed. In the past, the propulsive force is generally controlled by changing the reflectivity of a thin film, but this paper proposes a new method to control the propulsive force of light pressure by the structure of an object, and demonstrates the calculation process and the demonstration. This is a new design method for solar sails.

Presentation Details:

Optical systems with balanced losses and gains may give unique platforms similar to classical quantum systems. In this paper, we show that parity-time (PT) symmetry breaking occurs in optical resonators in which light is densely collected such that nonlinear effects are enhanced. This is an unfamiliar field, but I will try to explain it as clearly as possible in my presentation.

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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.

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