Journal Club 2018 | Tanabe Photonic Structure Group

Journal Club

By fiscal year (April-December)

Fiscal Year 2018

Presentation Details:

Electronics and photonics technologies are key technologies supporting industry, but the integration of these two technologies on-chip has been a major challenge for some time. However, the cost of applying these technologies to a large number of applications is prohibitive.
Therefore, this study integrates photonics technology into the CMOS process by introducing a polycrystalline silicon layer. This has enabled the integration of various optical elements, such as waveguide structures, high-speed modulators, and photodetectors, on a single chip using a CMOS process together with transistors.

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In this paper, we have proposed a metal-insulator-metal (MIM) pressure sensor which consists of two plasmonic waveguides and a double square ring resonator. The two square rings are connected via a rectangular patch located between the two of them. The finite-difference time-domain method (FDTD) has been used to simulate the device. Applying a pressure on the structure, it deforms, and a red shift of 103nm in the resonance wavelength has been calculated. The proposed optical plasmonic pressure sensor has a sensitivity of 16.5nm/MPa which The proposed optical plasmonic pressure sensor has a sensitivity of 16.5nm/MPa which makes it very suitable for use in biological and biomedical engineering.

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The ability to optically capture nanoscale particles in a reliable and non-invasive manner has emerged as an important capability for nanoscience. Therefore, various techniques have been introduced for the capture of nanoscale particles, including plasmonic nanostructures. However, nano-optical tweezers based on plasmonics face the problem of Joule heating due to high losses in metals. Here, this study experimentally demonstrates a non-plasmon approach, namely optical trapping and transport of nanoparticles using silicon nano-antennas. Here polystyrene nanoparticles with diameters of 20 and 100 nm were captured and fluorescence microscopy was used to track their position as a function of time. This showed that multiple nanoparticles can be captured simultaneously by a single nano-antenna. We also showed simulations of the nanoantennas that predict enhanced optical forces with only a small amount of heat generation. This study demonstrates that silicon nanoantennas can optically confine nanoparticles without detrimental thermal heating effects.

Presentation Details:

"Lateral graphene p-n junctions are important since they constitute the core components in a variety of However, formation of lateral graphene p-n junctions with a controllable doping levels is still a great challenge due to the monolayer feature of graphene. Herein, by performing selective ion implantation and in situ growth by dynamic chemical vapor deposition, direct formation of seamless graphene p-n junctions with a controllable doping levels is still a great challenge due to the monolayer feature of graphene. Herein, by performing selective ion implantation and in situ growth by dynamic chemical vapor deposition, direct formation of seamless lateral graphene p-n junctions with spatial control and tunable doping is demonstrated. Uniform lattice substitution with het- eroatoms is achieved in both the boron-doped and nitrogen-doped regions and photo- electrical assessment As ion implantation is a standard technique in microelectronics, our study suggests a simple and effective strategy for mass production of graphene p-n junctions with batch capability and spatial controllability, which can be readily integrated into the production of graphene-based electronics and photonics.", cited from [Gang Wang, et al "Seamless lateral graphene p-n junctions formed by selective in situ doping for high-performance photodetectors", Nature Communicationsvolume 9, Article number: 5168 (2018).

Presentation Details:

Detection of weak radial velocity shifts of host stars induced by orbiting planets is an important technique for discovering and characterizing planets Optical frequency combs enable calibration of stellar radial velocity shifts at levels required for detection of Earth analogs. A new chip-based device, the Kerr soliton microcomb, has properties ideal for ubiquitous application outside the lab and even in future space-borne instruments. Moreover, microcomb spectra are ideally suited for astronomical spectrograph calibration and eliminate filtering steps Here, for the calibration of astronomical spectrographs, we demonstrate an Efforts to search for the known exoplanet HD 187123b were conducted at the Keck-II telescope as a first in-the-field demonstration of microcombs.

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The IoT uses many wireless sensors to obtain data on the physical environment (temperature, humidity, and air pressure) and has a variety of possible applications, including environmental measurement, healthcare sensors, smart cities, and precision agriculture. Wireless sensors collect, analyze, and transmit data about the environment. In general, wireless sensors used in IoT are mainly composed of electronic devices that may be subject to electromagnetic interference in many situations. Optical sensors are not affected by electromagnetic interference and offer significant advantages in harsh environments. Furthermore, by introducing optical resonance to enhance the interaction of light, resonator-based optical sensors can significantly increase the capability and flexibility of wireless sensors by providing compact, sensitive, and versatile functionality. This study provides the first demonstration of a wireless photonic sensor node based on a whispering gallery mode (WGM) optical resonator.

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Recently, there has been much research on beams with orbital angular momentum (OAM), such as optical vortices, but devices that not only detect but also measure specific values have been limited to the bulk size. In this study, we have created a micro OAM measurement device using a new CMOS-compatible plasmonic topological insulator Sb2Te3.
The proposed topological insulator has superior characteristics in the ultraviolet to visible light range compared to conventionally used materials such as Au, and enables highly accurate OAM measurements with crosstalk of -20dB or less.
Topological insulators, OAMs, and surface plasmon polaritons will also be briefly introduced.

Presentation Details:

Optical gyroscopes can detect rotational velocity by using the Sagnac effect. Gyroscopes based on this principle are very suitable for miniaturization on nanophotonic structures. However, the signal-to-noise ratio of gyroscopes is generally limited by thermal fluctuations and fabrication mismatches. Because of this relatively small signal strength at the microscale, integrated nanophotonic gyroscopes have not been realized until now.
In this study, a new method called "reciprocal sensitivity enhancement" was used to suppress thermal fluctuations and fabrication mismatches, resulting in an ultra-compact gyroscope. The gyroscope is 500 times smaller than conventional fiber-optic gyroscopes, yet 30 times more sensitive.

Presentation Details:

The Nobel Prize in Physics 2018 has been awarded one half to Arthur Ashkin for the optical tweezers and their application to biological systems, and the other half jointly to Gérard Mourou and Donna Strickland for their method of generating high-intensity, ultra-short optical pulses. Dr. Strickland is the third woman among the 210 laureates who have received the nobel prize. In the presentation, a brief look at the scientific work awarded this year will be In the presentation, a brief look at the scientific work awarded this year will be introduced, then the newest work by Dr. Strickland's group will be shown, where they reported a compact, high-average-power, sub-picosecond, two-color (1025 and 1085 nm) fiber-coupled, chirped pulse amplification Yb:fiber laser.

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Crystal resonators have attracted attention as a fundamental platform for a very wide variety of applications, including soliton generation, low-noise microwave generation, and frequency stabilization.
Therefore, in this study, we achieved highly efficient coupling on-chip by inserting light from a silicon nitride waveguide into a silica waveguide with an air-bridged structure.
This method is more robust and suitable for packaging compared to coupling using tapered fibers.

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Electronic oscillator circuits are used in a lot of domains going from telecommunications to clock generation. These non-idealities of electronic oscillator circuits are a motivation for the design of These non-idealities of electronic oscillator circuits are a motivation for the design of opt-electronic oscillators.

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Erbium doped fiber amplifier is a key device in WDM/DWDM technology. The task of modeling EDFA is computationally expensive. In this paper we investigate the application of multilayered feed-forward neural network to model an EDFA.

Presentation Details:

In recent years, cellulosic materials have attracted renewed interest as a substitute for conventional plastics in the face of environmental problems. In this study, we fabricated photonic and plasmonic structures made of hydroxypropyl cellulose (HPC) using soft lithography. The cellulose photonic crystals are bio-applicable and degradable in various solvents such as water, and can be colored by photonic structures and enhanced by photoluminescence. Furthermore, we show that the plasmonic crystals can be used as surface-enhanced Raman spectroscopy by forming plasmonic crystals with a metal coating.

Presentation Details:

An optofluidic dye laser integrating an optical cavity into a microfluidic device enables sensitive detection of small amounts and low concentrations of objects. In this study, we have realized a Förster resonance energy transfer (FRET)-based multicolor laser using a microdroplet optical resonator. Here, we generated monodisperse microfluidic droplets with the introduction of coumarin 102. The spherical droplets acted as a whispering gallery-mode optical resonator and were raged at a wavelength of about 470 nm. The composition of the gain medium in the droplet resonator can be changed, and the wavelength can be changed from blue to orange (~590 nm) by introducing Rhodamine 6G into the flowing droplet. No coumarin 102 emission was observed during the Rhodamine 6G raging. The ability to control the color of the raging in the same droplet resonator, as shown in the present study, makes it possible to continuously detect multiple types of target molecules in or around the resonator.

Presentation Details:

Fiber-to-chip and chip-to-chip interfaces have long been a challenge in photonics device integration. Conventional approaches require high-precision alignment and precise consideration of adjustment of mode characteristics. In this study, 3D-printed beam forming elements are formed on the end faces of fibers and chips to improve coupling efficiency. In addition, the beam shape and propagation direction are adjusted with 3D-printed free-form mirrors, and the beam is expanded with multiple lenses. This has resulted in a significant performance improvement in the integration of multiple chips.

Presentation Details:

The Internet sends hundreds of Tbit/s of information and consumes 9% of the world's electricity consumption. In order to reduce energy consumption, which is increasing at a rate of 20-30% annually, more efficient communication light sources are needed. In such an era trend, it is expected to save energy and space by using a single comb light source instead of many laser light sources at the same time. In this study, we have succeeded in generating a comb with an extremely high efficiency of 66% by using a waveguide made of AlGaAs. By using this comb light source for information communication, 661 Tbit/s was achieved.

Presentation Details:

Optical devices that allow light to propagate in only one direction, optical isolators, are important in a wide range of applications. Non-opposing propagation of sound waves can be realized by using a rotating mechanical element. In this study, we applied the same idea to light waves and attempted to realize an optical isolator. However, since light waves are much faster than sound waves, a considerable rotation speed is required to achieve the same effect. The high rotational speed also causes axial blurring, making it difficult to maintain the distance between the resonator and the waveguide, and critical coupling cannot be maintained. As a result, other methods of isolation have been employed.
Therefore, we realized coupling at a distance of several nanometers from the resonator by utilizing the principle that the magnetic head emerges from the disk with nanometer accuracy in terms of hydrodynamics in HDDs. In this experiment, we achieved 99.6% isolation by splitting the clockwise and counterclockwise modes by rotating the resonator at high speed.

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Intelligent Transport Systems (ITS) is an infrastructure technology used to control traffic signals. In this study, we proposed a radar sensor that can simultaneously perform the three technical tasks required for ITS: traffic volume measurement, speed measurement, and vehicle type distinction.

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Soft materials that change shape in response to stimuli such as heat, light, and magnetic fields have the potential for numerous applications ranging from flexible electronics and soft robotics to biomedical issues such as drug delivery and tissue engineering. In particular, the use of magnetic fields is promising for medical applications that require materials to be remotely manipulated and moved in a closed space, but current fabrication methods can only induce simple shape changes.
This study presents a technique for printing soft materials that are magnetically activated and deform in less than a second. by magnetizing the nozzle of a 3D printer and controlling the arrangement of ferromagnetic microparticles in a silicone rubber matrix, structures can be fabricated that are reversible and dynamically deformable. The fabricated materials can be programmed to perform a variety of useful actions, such as spinning, jumping, and grasping objects, and are expected to have a wide range of applications.

Presentation Details:

Optical frequency combs with equally spaced frequency components are the basis of modern frequency metrology, precision spectroscopy, astronomical spectroscopy, ultrafast optics, and quantum information engineering. Chip-scale frequency combs, which take advantage of nonlinearities such as the Kerr and Raman effects in monolithic microcavities with ultra-high Q-values, have recently progressed with the observation of temporal resonator solitons. However, it is generally difficult to tune the wavelength dispersion in a laser resonator, which determines the formation of an optical comb, by an electric field, both in microcavities and fiber resonators. Such electrical dynamic control couples optical frequency combs with optoelectronics, enabling the output of various optical combs in a single resonator with fast and convenient tunability. Due to the extraordinary Fermi-Dirac tunability and ultrafast carrier mobility, graphene has a complex optical dispersion determined by its optical conductivity, which can be tuned by a gate voltage. Here we introduce gate-tunable optical conductivity into a silicon nitride micro-optical resonator and demonstrate intracavity tunability of a graphene-based gated optical frequency comb by varying the second-order and higher-order wavelength dispersion.

Presentation Details:

In the report we demonstrate how, using laser light, effectively trap gas bubbles and transport them through a liquid phase to a desired destination by shifting the laser beam position. The physics underlying the effect is complex but quite general as it comes from the limited to two-dimension, well-known, Marangoni effect. The experimental microscope-based system consists of a thin layer of liquid placed between two glass plates containing a dye This point-like heat source locally changes surface tension of nearby liquid-air interface. Because of temperature gradients a photo-triggered Marangoni flows are induced leading to self-amplification of the effect and formation of large-scale whirls. The interface is bending toward beam position allowing formation of a gas bubble upon suitable beam steering. Using various techniques (employing luminescent particles or liquid crystals), we visualize liquid flows propelled by the tangential to interface forces. This helped us to understand the physics of the phenomenon and analyze accompanying effects leading to gas bubble trapping. The manipulation of sessile droplets moving on the glass surface induced via controlled with laser light interface bending (i.e. "droplet catapult") is demonstrated as well.

Presentation Details:

In modern cancer treatment, biopsy methods require histological molecular and genomic analysis. Accurately locating and adequately sampling in a single step in cancers with intratumoral heterogeneity is important to reduce patient risk. In this study, we proposed a technique that enables in situ cancer cell identification during collection by Raman spectroscopy and demonstrated cancer detection.

Presentation Details:

Lightweight and mechanically flexible optoelectronic devices can be fabricated using organic semiconductors. However, most organic semiconductor lasers still remain "rigid" because they require a substrate to support them. In this study, we fabricated an ultrathin (<500 nm) film-type DFB laser without a substrate using a simple fabrication process, and achieved ultra-light weight and high flexibility. This lightweight and flexible DFB laser can be incorporated into contact lenses, banknotes, etc., and is expected to be used in security and medical applications in the future.

Presentation Details:

In this study, we succeeded in producing spontaneous chirality in silicatroid resonators without breaking the PT symmetry. This circular dichroism is caused by nonlinear effects on the coupling between CW and CCW. It was experimentally demonstrated that when the input light intensity exceeds a threshold of several hundred uW, the nonlinear effect causes a circular dichroism of about 20:1.

Presentation Details:

Soft robots are safe robots that can adapt well to humans and the natural environment. However, it is difficult to fabricate all parts of a soft robot using soft materials, and it is necessary to use metals for some parts. In this study, an octopus-shaped soft robot was developed that uses soft materials for all parts without using metals or other materials. Furthermore, the robot does not need to be connected to an external power source, and can be made autonomous by using a catalytic reaction.

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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.

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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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