Design of graded-index type photonic crystal fiber with uniform air hole diameter and its application to collimator for single-mode photonic crystal fiber　　　　　　　　　　　　　　　
Daichi Yoshihara; Hirohisa Yokota; You Imai, Corresponding
Optical Review, 07 Nov. 2023, [Reviewed]

Design of terahertz fibers using polymer tube bundles and their guided mode and propagation loss analyses　　　　　　　　　　　　　　　
H. Yokota; K. Onuki; Y. Imai, Lead, Elsevier
Optics Communications, 18 Sep. 2020, [Reviewed]

Design of graded index type photonic crystal fiber having α‐power air hole diameter distribution with α<1 for fiber collimator application
Mizuki Wakabayashi; Hirohisa Yokota; Yoh Imai, Corresponding, Springer Japan
Optical Review, 09 Aug. 2019, [Reviewed]

Optical coupling characteristics of graded‐index type photonic crystal fiber collimator depending on air hole diameter ratio to pitch
Mizuki Wakabayashi; Hirohisa Yokota; Yoh Imai, Corresponding, Springer Japan
Optical review, 29 Jul. 2019, [Reviewed]

Design of graded index type photonic crystal fiber having α-power air hole diameter distribution with α<1 for fiber collimator application　　　　　　　　　　　　　　　
M. Wakabayashi; H. Yokota; and Y. Imai
11th International Conference on Optics-photonics Design & Fabrication (ODF'18) Tech. Dig., 28 Nov. 2018, [Reviewed]

Propagation characteristics in PCF with tapered air holes for fiber connecting devices　　　　　　　　　　　　　　　
K. Koizumi; H. Yokota; and Y. Imai
11th International Conference on Optics-photonics Design & Fabrication (ODF'18) Tech. Dig., 28 Nov. 2018, [Reviewed]

Variable photonic crystal fiber optical attenuator combining air hole reduction induced radiation and bending loss
Hirohisa Yokota; Tomohiko Sano; Yoh Imai, Recently, an optical attenuator has been important in fiber optic communication systems, because a transmission power in fiber has become higher due to a channel increment in wavelength division multiplexing transmission. A photonic crystal fiber (PCF) optical attenuator is fabricated by air hole diameter reduction in a part of PCF in which radiations are caused in the air hole diameter reduced part of PCF. A PCF optical attenuator has a high power resistance feature due to its radiation-induced operation of optical attenuation. In this paper, we proposed a variable PCF optical attenuator in which a bend was applied to the air hole diameter reduced part in PCF optical attenuator that was fabricated by CO2 laser irradiation. In PCF optical attenuator fabrication, the attenuation was adjusted by the reduced air hole diameter with laser irradiation time control. It was demonstrated that 10.6–13.5 dB of variable attenuation was obtained at 1550 nm-wavelength with 0°–90° bending angle applied to the air hole diameter reduced part in PCF optical attenuator., SpringerOpen
Optical Review, 01 Jun. 2018, [Reviewed]

Connection loss reduction in variable optical delay line by using graded-index type photonic crystal fiber
Keiichi Higuchi; Hirohisa Yokota; Kazuki Yoneya; Yoh Imai, A low-loss butt-joint connection method between photonic crystal fibers (PCFs) by using a graded-index type photonic crystal fiber (GI-PCF) is proposed. The GI-PCF, in which the diameter of the air holes is chosen in a parabolic distribution in the effective refractive index, is analyzed numerically by a beam propagation method. It is found that the mode extent in the GI-PCF varies periodically along the propagation direction when the LP01 mode of the PCF is launched into the GI-PCF. This characteristic is successfully applied to reduce the butt-joint connection loss between the PCFs by 1.6 dB with a 20.6-mm GI-PCF under 200 µm air gap. © 2018 Institute of Electrical Engineers of Japan. Published by John Wiley &
Sons, Inc., John Wiley and Sons Inc.
IEEJ Transactions on Electrical and Electronic Engineering, 01 May 2018, [Reviewed]

Coupling characteristic adjustment of photonic crystal fiber coupler with length control of air hole collapsed region　　　　　　　　　　　　　　　
Hirohisa Yokota; Yu Nakajima; Yoh Imai; Yutaka Sasaki, Lead, International Journal of Photonics and Optical Technology
International Journal of Photonics and Optical Technology, 30 Sep. 2017, [Reviewed]

Optical characteristic variations in gamma ray irradiated polarization-maintaining optical fibers
Hirohisa Yokota; Yosuke Kameda; Yoh Imai, Polarization-maintaining ( PM) optical fibers are introduced in fiber optic communication systems and optical fiber sensors to improve their performances. It is known that characteristics of optical fibers vary for radiation exposures, e.g., a transmission loss increment. It is important to clarify the characteristic variations of PM fibers by radiations in their applications. The radiation induced optical characteristic variation is also useful for an application of optical fibers including PM fibers as radiation sensors. In this paper, optical characteristic variations in gamma ray irradiated PM optical fibers with low modal birefringence were experimentally clarified indenting to apply a polarization optical time domain reflectometry to a distributed radiation sensor. It was confirmed that the transmission losses for both polarization modes in elliptical jacket fibers increased similar to ordinary silica based single-mode fibers, where the difference of transmission losses of two polarization modes was enhanced by the irradiation. We also clarified that the modal birefringence of the elliptical jacket fibers increased for the irradiation for the first time by the beat length measurement using the wavelength sweeping technique., OPTICAL SOC JAPAN
OPTICAL REVIEW, Apr. 2017, [Reviewed]

Light propagation characteristics in photonic crystal fibers with alpha-power profiles of air hole diameter distributions and their application to fiber collimator
Hirohisa Yokota; Keiichi Higuchi; Yoh Imai, Light propagation characteristics in photonic crystal fibers (PCFs) with alpha-power profiles of air hole diameter distributions were theoretically investigated. It was clarified that the intensity peak of the beam propagating in the PCF with Gaussian beam excitation varied periodically with little power attenuation. It was found that the envelope of the periodic intensity variation depended on a. We theoretically demonstrated that the PCF with the alpha-power profile of the air hole diameter distribution could be applied to a collimator for a conventional PCF with uniform air holes in Gaussian beam excitation to reduce coupling loss, where a PCF of appropriate length with the alpha-power air hole diameter distribution was spliced to a conventional PCF. It was also found that the coupling efficiency was higher for a larger alpha. (C) 2016 The Japan Society of Applied Physics, IOP PUBLISHING LTD
JAPANESE JOURNAL OF APPLIED PHYSICS, Aug. 2016, [Reviewed]

Coupling Characteristics of Fused Optical Fiber Coupler Formed with Single-Mode Fiber and Photonic Crystal Fiber Having Air Hole Collapsed Taper
Hirohisa Yokota; Hirotomo Yashima; Yoh Imai; Yutaka Sasaki, Fused coupler forming with a single-mode fiber (SMF) and a photonic crystal fiber (PCF) is one of the solutions for optical coupling from a light source to a PCF. In this paper, we presented coupling characteristics of a fused fiber coupler formed with an ordinary SMF and a PCF having air hole collapsed taper. A prototype of SMF-PCF coupler with air hole collapsed taper was fabricated using CO2 laser irradiation. The coupling efficiency from SMF to PCF was -6.2 dB at 1554 nm wavelength in the fabricated coupler. The structure of the SMF-PCF coupler to obtain high coupling efficiency was theoretically clarified by beam propagation analysis using an equivalent model of the coupler with simplification. It was clarified that appropriately choosing the prestretched or etched SMF diameter and the length of air hole collapsed region was effective to obtain high coupling efficiency that was a result of high extinction ratio at cross port and low excess loss. We also demonstrated that the diameter of prestretched SMF to obtain high coupling efficiency was insensitive to the air hole diameter ratio to pitch of the PCF in the air hole collapsed SMF-PCF coupler., Hindawi Limited
Advances in OptoElectronics, 2016, [Reviewed]

Fabrication of photonic crystal fiber optical attenuators with air hole diameter control using CO2 laser irradiation technique
Hirohisa Yokota; Kosuke Ushiroda; Naoya Inoue; Yoh Imai; and Yutaka Sasaki, Lead, Photonic crystal fiber (PCF) optical attenuators with air hole diameter control were fabricated by PCF fusion using CO2 laser irradiation technique. The diameters of air holes in the PCF cross-section were equally decreased by laser irradiation with a PCF rotation. We demonstrated that the air hole diameter or the air hole diameter ratio to pitch could be adjusted by the irradiated laser power. It was clarified that the larger attenuation could be obtained for the smaller air hole diameter ratio to pitch. The attenuation was controlled from 5 dB to 20 dB at 1550 nm-wavelength for the air hole diameter ratio to pitch from 0.35 to 0.225, where the length of air hole diameter controlled region was 10 mm. It was also clarified that the fabricated PCF optical attenuators exhibited good wavelength independent characteristics for 980 nm-, 1310 nm-, and 1550 nm-wavelengths. (C) 2015 Elsevier Inc. All rights reserved., ELSEVIER SCIENCE INC
Optical Fiber Technology, 01 Jun. 2015, [Reviewed]

Measurements of nonlinear refractive index of optical fiber by using multiple interference in OFRR　　　　　　　　　　　　　　　
Y. Imai; H. Yokota; S. Yamauchi
J. Photonics and Optoelectronics, 01 Jul. 2013, [Reviewed]

Fabrication of polarization-maintaining photonic crystal fiber coupler with air hole state control using CO2 laser irradiation technique
H. Yokota; Y. Ito; H. Kawashiri; H. Kiue; H. Tobita; Y. Imai; Y. Sasaki, Lead, Polarization-maintaining photonic crystal fiber couplers (PM-PCFCs) were fabricated using a CO2 laser irradiation technique. We could control the states of air holes in the tapered region of couplers by adjusting the laser power density in the fusion and the elongation processes. It was demonstrated that the air hole remaining PM-PCFC exhibited polarization-splitting characteristics and that the air hole collapsed PM-PCFC had polarization insensitive coupling characteristics., IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG
IEICE Transactions on Electronics, 01 Oct. 2012

Reduction of splice loss between single-mode optical fiber and high nonlinear photonic crystal fiber by air hole diameter control with CO2 laser irradiation
Hirohisa Yokota; Hirotomo Yashima; Yoh Imai; Yutaka Sasaki, Lead, 単一モード光ファイバとモードフィールド径（MFD）の小さい高非線形フォトニック結晶ファイバの接続時に生じるMFD不整合損失の低減法として，CO2レーザ照射による空孔径制御を用いることを提案し，その有効性を理論的・実験的に明らかにした．, The Institute of Electronics, Information and Communication Engineers
IEICE Transaction on Electronics (Japanese Edition), 01 Feb. 2011, [Reviewed]

Coherence effect on decryption characteristics in message modulation type chaos secure communication systems using fiber-optic ring resonators
Yoh Imai; Satoshi Yamauchi; Hirohisa Yokota; Takehito Suzuki; Kansuke Tsuji, We numerically investigated the dependence of the decryption characteristics in a message modulation type chaos secure communication system using optical fiber ring resonators (OFRRs) on the coherence condition of carrier light. Since the output dynamics of OFRRs were formed on the basis of interference phenomenon among the circulated components in OFRRs, the coherence condition of input light affected inherently the OFRR output dynamics, resulting in the decryption characteristics. It was found that the decryption characteristics degraded as coherence length increased, i.e., as the spectral width of the input light decreased. The decryption characteristics also grew worse as the parameter differences between the transmitter and the receiver became larger. (C) 2009 Elsevier B.V. All rights reserved., ELSEVIER SCIENCE BV
Optics Communications, 15 Oct. 2009, [Reviewed]

Demonstration of an all-optical switching operation using an optical fiber grating coupler
H. Yokota; M Kobayashi; H. Mineo; N. Kagawa; H. Kanbe; Y. Sasaki, Lead, An optical fiber grating coupler (FGC) is a fused optical fiber coupler with a tapered region in which refractive index-modulated gratings are written. In the FGC, the light with specific wavelength satisfying the Bragg condition of the grating can be dropped to one output port and other lights are transmitted to another output port when lights with various wavelengths are launched into the input port. The FGC can operate as an all-optical switch by controlling the Bragg wavelength of the grating using a third order nonlinear optical effect caused by a control light that are launched with a signal light. In this paper, an all-optical switching operation due to a third order nonlinear optical effect in an FGC is first demonstrated for a signal light with 1.55 mu m-wavelength to be changed from one port of the FGC to another one by the 720 W peak of a control light from a Nd:YAG laser with 1.06 mu m-wavelength. The switching efficiency obtained was similar to 7%. It was clarified that a longer pulse length of the control light compared to the grating length is required to obtain a large Bragg wavelength shift for the switching. It was also clarified that the Bragg wavelength shift is caused by a third order nonlinear effect and a photothermal effect. A contribution of the photorthermal effect was estimated. We also estimated the switching efficiency for pump power in the FCC switch. (C) 2008 Elsevier B.V. All rights reserved., ELSEVIER SCIENCE BV
Optics Communications, 01 Oct. 2008, [Reviewed]

Designs and fabrications of photonic crystal fiber couplers with air hole controlled tapers
Hirohisa Yokota; Hiroki Kawashiri; and Yutaka Sasaki, Lead, For the construction of photonic crystal fiber (PCF) systems using their unique properties, a PCF coupler (PCFC) is one of the key components of the systems. The characteristics of the PCFC depend on the state of air holes in the tapered region of the PCFC because the state of air holes in the tapered region affects light propagation in the PCFC taper. In this paper, coupling characteristics of PCFCs were theoretically investigated. In PCFCs with air hole remaining tapers, we found that a smaller elongation ratio i.e. a stronger elongation is required to obtain optical coupling as an air hole pitch or a ratio of air hole diameter to pitch is larger. In PCFCs with air hole collapsed tapers, it was clarified that a dependence of extinction ratio on air hole collapsed elongation ratio is higher for smaller elongation ratio. It was also clarified that an air hole remaining PCFC has slow wavelength characteristics in extinction ratio compared to an air hole collapsed PCFC. Air hole remaining PCFCs and air hole collapsed PCFCs were fabricated using a CO2 laser irradiation technique. We could successfully control whether air holes in the PCFC taper were remaining or collapsed by adjusting the irradiated laser power in the elongation process of the PCFC fabrication. It was experimentally clarified that the air hole remaining PCFC has slow wavelength characteristics in extinction ratio compared to the air hole collapsed PCFC. The tendencies of the measured wavelength characteristics of PCFCs agree with those of numerical results., IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG
IEICE Transactions on Electronics, 01 Jul. 2008, [Reviewed]

CO2レーザ照射法を用いたフォトニック結晶ファイバカプラの作製　　　　　　　　　　　　　　　
横田浩久; 小林善博; 木植秀之; 飛田英夫; 佐々木豊, Lead, CO2レーザ照射法を用いてフォトニック結晶ファイバカプラを作製した．延伸時の張力が一定値に保たれるようにレーザパワーを調整することにより，テーパ部の空孔を残したカプラを作製することができた．作製したカプラの消光比は平たんな波長特性を示した．
電子情報通信学会論文誌, 01 Aug. 2007, [Reviewed]

All-fiber optical add-drop multiplexer using a pair of fiber grating couplers
Hirohisa YOKOTA; Jun-ichi IGARASHI; Yoshitaka SATODA; Satoru OHUCHI; Yutaka SASAKI, Lead, A new all-fiber optical add-drop multiplexer (ADM) using a pair of fiber grating couplers (FGCs) was proposed and first demonstrated. It was theoretically and experimentally shown that both drop and add efficiencies could be maximized in the proposed ADM. It was also clarified that the crosstalk between dropped and added signals could be improved in the proposed ADM compared with that in the single FGC. Drop and add operations in the ADM for 3-channel WDM signals with 1.6 nm wavelength spacing were confirmed. The ADM with signal amplification ability, which consists of a pair of FGCs, an EDF, and a pump-LD, was proposed and demonstrated. It was confirmed that the dropped and transmitted optical signals could be amplified in the ADM, and would be able to expand fiber routing spans., Optical Society of Japan
Optical Review, 01 Jun. 2002, [Reviewed]

An ASE reduction filter using cascaded optical fiber grating couplers in EDFA repeater
Hirohisa YOKOTA; Kenji KAMOTO; Jun-ichi IGARASHI; Norihiko MOURI; Yutaka SASAKI, Lead, A new configuration for an ASE reduction filter in EDFA repeaters for WDM optical transmission systems using optical fiber grating couplers (FGCs) was proposed and first demonstrated. The filtering characteristics of the proposed filter for amplified single wavelength signal and 2-channel WDM signals using EDFA were identified. It was found that the filter was effective to improve SNR in optical domain by reducing ASE noise. The required FGC characteristics for the filter were theoretically predicted under the condition that the total filter loss did not exceed 3 dB. More than 70% of drop efficiency was required in each FGC for the application of the proposed filter to an 8-channel WDM system using EDFA repeaters.
Optical Review, 01 Feb. 2002, [Reviewed]

Characteristics of fused optical fiber grating couplers with tapered shapes
Hirohisa YOKOTA; Takahiro HASEGAWA; Yoshitaka SATODA; Eiichi SUGAI; Yutaka SASAKI, Lead, Fused optical fiber grating couplers (FGCs), in which Bragg gratings are written in the coupling regions of fused optical fiber couplers with tapered shapes along them are theoretically and experimentally investigated. By coupled mode analysis considering these tapered shapes, the drop efficiencies of the FGCs, which are inherently zero for the normal fiber couplers without grating, are calculated. The grating offset, which is the difference between the centers of grating and the coupler taper, is found to be effective to increase the drop efficiency of the FGC. It is determined that the tapered shapes influence the wavelength dependence of the drop efficiency and tolerate the grating offset precision. Apodizations for the grating of FGC are found to be effective in suppressing side lobes of the drop efficiency. Measurement of the wavelength characteristics of drop efficiency and the temperature characteristics of drop wavelength of the fabricated fused FGC confirm that the lightwave with specific wavelength can be dropped by the FGC and that the temperature dependence of the drop wavelength is similar to that of Bragg wavelength changes of usual fiber Bragg gratings., Optical Society of Japan
Optical Review, 01 Jun. 1999, [Reviewed]

Design of polarization-maintaining optical fiber suitable for thermally-diffused expanded core techniques
Hirohisa YOKOTA; Emiko OKITSU; Yutaka SASAKI, Lead, Thermally-diffused expanded core (TEC) techniques brought the fibers with the mode fields expanded by thermal diffusion of core dopants. The techniques are effective to the reduction of splice or connection losses between the different kind of fibers. and are applied to the integrations of thin film optical devices in fiber networks, the fabrications of chirped fiber gratings, and so on. In the practical use of TEC techniques. the fibers are heated high temperature of about 1650 degrees C because of a short period of time in processing by microburners. The mode field diameter expansion (MFDE) ratio, which is defined as the ratio of the mode field diameter in the fiber section having the core expanded and that unexpanded, is desired to be more than 2.0 from the viewpoint of loss reduction in industrial uses of the TEC techniques. When the TEC techniques are applied to polarization-maintaining optical fibers (PM fibers), such as PANDA fibers. both core dopants and stress applying part (SAP) dopants diffuse simultaneously. So the MFDE ratio is less than two without mode field deformation in conventional PANDA fibers which are practically used as PM fibers. In this paper a PANDA fiber design suitable for the TEC techniques is newly proposed. The fiber has 1.28 mu m cutoff wavelength and the mode field diameter is about 11 mu m before core expansion at 1.3 mu m wavelength. As the result of our design by the stress analysis, it is shown that the MFDE ratio in the newly designed PANDA fiber can take 2.0 without mode field deformation under the condition that a modal birefringence is more than 1.5 x 10(-4). The MFDE ratio with newly designed PANDA fiber can be larger than that in the conventional PANDA fiber. The mode fields in the fiber sections having the cores expanded and unexpanded are calculated by the finite difference beam propagation method. When the MFDE ratio takes about 2.0. the small mode field noncircularity of 49% in the newly designed PANDA fiber is gained in comparison with that of 110% in the conventional PANDA fiber., IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG
IEICE Transactions on Communications, 01 Apr. 1997, [Reviewed]

Optical irradiation method for fiber coupler fabrication　　　　　　　　　　　　　　　
Hirohisa YOKOTA; Eiichi SUGAI; Yutaka SASAKI, Lead, An optical irradiation method for high-speed fiber coupler fabrications without contamination is proposed. In optical fiber taper fabrications we found an interesting effect that fiber elongation is self-arrested although laser irradiation is continued. This is a typical effect in the optical irradiation method, but is not seen in the flame method or the thermal heating method.
The ``self-controlled fiber taper shape effect" is theoretically explained by considering thermal energy flows, and optical fiber couplers are fabricated using this effect. From our experiments, we show that optical fiber coupler fabrications at high-speed without contamination are possible using the optical irradiation method.
Optical Review, 01 Feb. 1997

非線形誘電体部を有する非対称光Y分岐回路素子の特性解析　　　　　　　　　　　　　　　
横田浩久; 倉薗貞夫, Lead
電子情報通信学会論文誌（C-I）, 01 Jun. 1995, [Reviewed]

Numerical analysis of an optical X coupler with a nonlinear dielectric region
Hirohisa YOKOTA; Koichi KIMURA; Sadao KURAZONO, Lead, For an application to the optical signal processing devices, we propose the optical X coupler which consists of two bending waveguides and a nonlinear dielectric region. To analyze this structure accurately we utilized the iterative finite difference beam propagation method (iterative FD-BPM). In this paper the formulation of the iterative FD-BPM for one wave and two waves cases are presented, respectively. We investigate following two cases. First, we consider the case that the light is launched into one of the input ports. We calculate the evolutions of the field amplitude and the transmission characteristics for the input power. Second, we consider the case that the signal light with the constant power is launched into one of the input ports and that the control light with the wavelength different from that of the signal light is launched into another input port. We calculate the evolutions of the field amplitude and the transmission characteristics of the signal light for the power of control light. As a result of the analysis, we show that all-optical switching operation is possible in the proposed structure., IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG
IEICE Transactions on Electronics, 01 Jan. 1995, [Reviewed]

非線形光導波路励振問題の反復差分ビーム伝搬法による解析　　　　　　　　　　　　　　　
横田浩久; 平雅文; 倉薗貞夫, Lead
電子情報通信学会論文誌（C-I）, 01 Oct. 1994, [Reviewed]

Light propagation characteristics in photonic crystal fiber with graded air hole diameters
Hirohisa Yokota; Kazuki Yoneya; Keiichi Higuchi; Yoh Imai
20th Microoptics Conf. (MOC’15) Tech.Digest, 23 Oct. 2015, [Reviewed]
Lead

A low loss butt-joint connection by using a graded-index photonic crystal fiber
Keiichi Higuchi; Hirohisa Yokota; Kazuki Yoneya; and Yoh Imai
20th Microoptics Conf. (MOC’15) Tech.Digest, 23 Oct. 2015, [Reviewed]

Fabrication of polarization-maintaining photonic crystal fiber optical attenuator using air hole diameter control　　　　　　　　　　　　　　　
H. Yokota; N. Inoue; Y. Kobayashi; Y. Imai
10th Conf. Laser and Electro-Optics Pacific Rim and 18th Optoelectronics and Communications Conf. / Photonics in Switching 2013 (CLEO-PR&OECC/PS 2013) Tech. Dig., 30 Jun. 2013, [Reviewed]
Lead

Terahertz fiber using polymer tube bundle
Y. Imai; H. Yokota; S. Yamauchi; T. Kuroda; M. Tonouchi
10th Conf. Laser and Electro-Optics Pacific Rim and 18th Optoelectronics and Communications Conf. / Photonics in Switching 2013 (CLEO-PR&OECC/PS 2013) Tech. Dig., 30 Jun. 2013, [Reviewed]

Recent progress in research on photonic crystal fiber devices
H. Yokota; Y. Imai
ICTON 2013 Conference Proceedings, 23 Jun. 2013, [Invited]
Lead

Estimation of fiber parameters by using OFRR nonlinear dynamics
Y. Imai; S. Yamauchi; H. Yokota; and S. Wei
Proceedings of 22nd General Congress of the International Commission for Optics, 15 Aug. 2011, [Reviewed]

Determination of stereoisomer in sugars by THz-TDS
S. Yamauchi; Y. Imai; H. Yokota; and M. Tonouchi
Proceedings of 22nd General Congress of the International Commission for Optics, 15 Aug. 2011, [Reviewed]

Fabrication of polarization-maintaining photonic crystal fiber couplers using CO2 laser irradiation technique
H. Yokota; Y. Ito; H. Kawashiri; Y. Imai; and Y. Sasaki
Proceedings of 21th International Conference on Optical Fiber Sensors, 15 May 2011, [Reviewed]
Lead

Measurement of nonlinear refractive index by using input-output characteristics in OFRR nonlinear dynamics
Y. Imai; S. Yamauchi; H. Yokota; and S. Wei
Proceedings of 21th International Conference on Optical Fiber Sensors, 15 May 2011, [Reviewed]

Fabrication of Photonic Crystal Fiber Attenuator with Air Hole Diameter Control Using CO2 Laser Irradiation
Hirohisa Yokota; Kousuke Ushiroda; Tomoyuki Takasugi; Yoh Imai; Yutaka Sasaki
15th OptoElectronics and Communications Conference (OECC2010) Technical Digest, 05 Jul. 2010, [Reviewed]
Lead

Fabrication of Tellurite Fiber Devices Using Laser Irradiation Techniques for All-Optical Switching Applications
Hirohisa Yokota; Yoh Imai; Yutaka Sasaki; Atsushi Mori
ICTON 2010 Conference Proceedings, 27 Jun. 2010, [Invited]
Lead

Air hole control for characteristic adjustment in air hole collapsed photonic crystal fiber coupler
Hirohisa YOKOTA; Yuu NAKAJIMA; Tomoya ICHIGE; Yoh IMAI; and Yutaka SASAKI
OECC2009 Technical Digest, 13 Jul. 2009, [Reviewed]
Lead

Photonic Crystal Fiber Devices Fabricated by Air Hole Control Using CO2 Laser Irradiation Technique
Hirohisa Yokota; Member; IEEE; Yoh Imai; and Yutaka Sasaki
ICTON 2009 Conference Proceedings, 28 Jun. 2009, [Invited]
Lead

Designs and fabrications of photonic crystal fiber couplers with air hole controlled tapers
Hirohisa Yokota; Hiroki Kawashiri; and Yutaka Sasaki
IEICE Transactions on Electronics, 01 Jul. 2008, [Reviewed]
Lead

Designs and fabrications of photonic crystal fiber couplers with air hole collapsed taper regions
Hirohisa Yokota; Hiroki Kawashiri; Hirotomo Yashima; and Yutaka Sasaki
OECC/IOOC2007 Technical Digest, 09 Jul. 2007, [Reviewed]
Lead

Photonic crystal fiber couplers with air hole remaining taper region for wavelength-flattened characteristics　　　　　　　　　　　　　　　
Hirohisa YOKOTA; Yoshihiro KOBAYASHI; Yutaka SASAKI
OECC2006 Technical Digest, 01 Jul. 2006, [Reviewed]
Lead

Laser trimming for adjustment of grating offset in phase-shifted fiber grating coupler for all-optical switching application　　　　　　　　　　　　　　　
Hirohisa YOKOTA; Yutaka SASAKI
OECC2003 Technical Digest, 19 Oct. 2003, [Reviewed]
Lead

All-optical switching by optical fiber grating coupler　　　　　　　　　　　　　　　
Yutaka SASAKI; Hiroyuki MINEO; Hirohisa YOKOTA; Yuichi SHIOJIRI; Hiroshi KANBE
Proceedings of ECOC2002, 08 Sep. 2002, [Reviewed]

Residual stress analysis for designs of fibers and fiber devices　　　　　　　　　　　　　　　
Hirohisa YOKOTA; Hiroshi FUJIMOTO; Yutaka SASAKI
OECC2002 Technical Digest, 08 Jul. 2002, [Reviewed]
Lead

EDFA gain monitoring by ASE level detection using optical fiber grating coupler　　　　　　　　　　　　　　　
Hirohisa YOKOTA; Kenji KAMOTO; Jun-ichi IGARASHI; Yutaka SASAKI
OECC/IOOC 2001 Conference Proceedings, 01 Jul. 2001, [Reviewed]
Lead

SNR improvement in EDFA repeaters using cascaded optical fiber grating couplers　　　　　　　　　　　　　　　
Hirohisa YOKOTA; Kenji KAMOTO; Jun-ichi IGARASHI; Norihiko MOURI; Yutaka SASAKI
OFC2001 Technical Digest, 19 Mar. 2001, [Reviewed]

Laser trimming method for adjustment of grating offset in optical fiber grating couplers　　　　　　　　　　　　　　　
Hirohisa YOKOTA; Jun-ichi IGARASHI; Yoshitaka SATODA; Satoru OHUCHI; Yutaka SASAKI
OECC2000 Technical Digest, 10 Jul. 2000, [Reviewed]
Lead

Add-drop multiplexers with signal amplification ability using optical fiber grating couplers　　　　　　　　　　　　　　　
Hirohisa YOKOTA; Yoshitaka SATODA; Jun-ichi IGARASHI; Satoru OHUCHI; Yutaka SASAKI
Proceedings of APCC/OECC1999, 18 Oct. 1999, [Reviewed]
Lead

Analysis of filtering charac-teristics of apodized optical fiber grating couplers　　　　　　　　　　　　　　　
Hirohisa YOKOTA; Yoshitaka SATODA; Takahiro HASEGAWA; Yutaka SASAKI
OECC98 Technical Digest, 12 Jul. 1998, [Reviewed]
Lead

Characteristics of optical fiber grating coupler with taper shape　　　　　　　　　　　　　　　
Hirohisa YOKOTA; Takahiro HASEGAWA; Eiichi SUGAI; Yutaka SASAKI
OECC97 Technical Digest, 08 Jul. 1997, [Reviewed]
Lead

Design of polarization-maintaining fiber suitable for thermally-diffused expansion techniques　　　　　　　　　　　　　　　
Hirohisa YOKOTA; Emiko OKITSU; Yutaka SASAKI
OECC96 Technical Digest, 16 Jul. 1996, [Reviewed]
Lead

Optical irradiation method for fiber coupler fabrications　　　　　　　　　　　　　　　
Hirohisa YOKOTA; Eiichi SUGAI; Yuji KASHIMA; Yutaka SASAKI
Proceedings of OFS-11, 21 May 1996, [Reviewed]
Lead

Ultrafast Opto-electronics　　　　　　　　　　　　　　　
Joint work
REALIZE Science & Emgineering, 31 Jul. 2003

数モードフォトニック結晶ファイバの設計　　　　　　　　　　　　　　　
鈴木凌輔; 横田浩久
令和4年度電気学会東京支部茨城支所研究発表会, 17 Dec. 2022, 電気学会東京支部茨城支所
20221217, 20221217

軸ずれ入射によるGI型フォトニック結晶ファイバセンサの高感度化　　　　　　　　　　　　　　　
吉田凌太郎; 横田浩久
令和4年度電気学会東京支部茨城支所研究発表会, 17 Dec. 2022, 電気学会東京支部茨城支所
20221217, 20221217

偏波保持ポリマーチューブ積層テラヘルツ波ファイバの設計　　　　　　　　　　　　　　　
前原亮太; 横田浩久
令和4年度電気学会東京支部茨城支所研究発表会, 17 Dec. 2022, 電気学会東京支部茨城支所
20221217, 20221217

偏波保持長周期ファイバグレーティング を用いた放射線センシングの研究　　　　　　　　　　　　　　　
令和3年度電気学会東京支部茨城支所研究発表会, 11 Dec. 2021
20211211, 20211211

グレーデッドインデックス型フォトニック結晶ファイバを用いた温度・歪みセンサの高感度化　　　　　　　　　　　　　　　
令和3年度電気学会東京支部茨城支所研究発表会, 11 Dec. 2021
20211211, 20211211

グレーデッドインデックス型フォトニック結晶ファイバを用いた温度歪みセンサー　　　　　　　　　　　　　　　
井関柊斗; 横田浩久
令和2年度電気学会東京支部茨城支所研究発表会, 06 Feb. 2021, 電気学会東京支部茨城支所

グレーデッドインデックス型フォトニック結晶ファイバを用いた温度歪みセン サー　　　　　　　　　　　　　　　
井関柊斗; 横田浩久
令和2年度電気学会東京支部茨城支所研究発表会, 06 Feb. 2021, 電気学会東京支部茨城支所

長周期ファイバグレーティングを用いた放射線センシングの研究　　　　　　　　　　　　　　　
吉田雄大; 横田浩久
令和2年度電気学会東京支部茨城支所研究発表会, 06 Feb. 2021, 電気学会東京支部茨城支所

Design of graded-index type photonic crystal fiber with uniform air hole diameter and its application to fiber collimator　　　　　　　　　　　　　　　
Daichi Yoshihara; Hirohisa Yokota; Yoh Imai
電子情報通信学会光ファイバ応用技術研究会, 08 Oct. 2020, 電子情報通信学会
20201008, 20201009

Theoretical study of temperature/strain sensor using graded-index type photonic crystal fiber　　　　　　　　　　　　　　　
Hirohisa Yokota; Shuto Iseki; Yoh Imai
電子情報通信学会光ファイバ応用技術研究会, 17 Jan. 2020, 電子情報通信学会
20200116, 20200117

ファイバ曲げを伴う大口径多モード光ファイバ伝送システムの周波数特性　　　　　　　　　　　　　　　
橘武; 横田浩久; 今井洋
令和元年度 電気学会東京支部茨城支所研究発表会, 07 Dec. 2019, 電気学会東京支部茨城支所

均一空孔径グレーデッドインデックス型フォトニック結晶ファイバのコリメー タへの応用　　　　　　　　　　　　　　　
吉原大智; 横田浩久; 今井洋
令和元年度 電気学会東京支部茨城支所研究発表会, 07 Dec. 2019, 電気学会東京支部茨城支所

空孔径縮小によるフォトニック結晶ファイバへの光結合向上　　　　　　　　　　　　　　　
其田悠佑; 横田浩久; 今井洋
令和元年度 電気学会東京支部茨城支所研究発表会, 07 Dec. 2019, 電気学会東京支部茨城支所

グレーデッドインデックス型フォトニック結晶ファイバを用いた歪みセンシングの理論検討　　　　　　　　　　　　　　　
横田浩久; 今井洋
2019年電子情報通信学会ソサイエティ大会, 13 Sep. 2019, 電子情報通信学会

ファイバブラッググレーティングを用いた放射線センシングの検討　　　　　　　　　　　　　　　
横田浩久; 篠崎政人; 若宮達也; 澤田一輝; 今井洋
第63回光波センシング技術研究会講演会, 12 Jun. 2019

単一モード光ファイバ用コリメータに適したグレーデッドインデックス型フォトニック結晶ファイバの設計　　　　　　　　　　　　　　　
野口一希; 横田浩久; 今井洋
平成30年度 電気学会東京支部茨城支所研究発表会, 17 Nov. 2018

ポイントバイポイント法による長周期ファイバーグレーティングの作製　　　　　　　　　　　　　　　
吉田壮太郎; 横田浩久; 今井洋
平成30年度 電気学会東京支部茨城支所研究発表会, 17 Nov. 2018

大口径多モードファイバ伝送システムにおけるファイバ曲げの影響　　　　　　　　　　　　　　　
橘武; 横田浩久; 今井洋
平成30年度 電気学会東京支部茨城支所研究発表会, 17 Nov. 2018

ファイバコリメータ用GI型フォトニック結晶ファイバの設計　　　　　　　　　　　　　　　
若林美月; 横田浩久; 今井洋
平成29年度 電気学会東京支部茨城支所研究発表会, 18 Nov. 2017, 電気学会東京支部茨城支所

偏波保持ファイバブラッググレーティングを用いた放射線センシング　　　　　　　　　　　　　　　
澤田一輝; 横田浩久; 今井洋
平成29年度 電気学会東京支部茨城支所研究発表会, 18 Nov. 2017, 電気学会東京支部茨城支所

大口径多モード光ファイバ伝送システムにおけるファイバ接続部隙間の影響　　　　　　　　　　　　　　　
福本純也; 渡部直樹; 横田浩久; 今井洋
平成29年度 電気学会東京支部茨城支所研究発表会, 18 Nov. 2017, 電気学会東京支部茨城支所

空孔径制御によるフォトニック結晶ファイバへの光結合効率向上の検討　　　　　　　　　　　　　　　
垣内進也; 横田浩久; 今井洋
平成29年度 電気学会東京支部茨城支所研究発表会, 18 Nov. 2017, 電気学会東京支部茨城支所

曲げ損失を用いた可変フォトニック結晶ファイバ光減衰器　　　　　　　　　　　　　　　
横田浩久; 佐野智彦; 今井洋
電子情報通信学会 光ファイバ応用技術研究会, 13 Oct. 2017, 電子情報通信学会

大口径多モード光ファイバのパラメータ推定における相関係数導入　　　　　　　　　　　　　　　
渡部直樹; 横田浩久; 今井洋
電子情報通信学会2017年ソサイエティ大会, 14 Sep. 2017, 電子情報通信学会

長周期フォトニック結晶ファイバグレーティングの挿入損失低減の検討　　　　　　　　　　　　　　　
二瓶弘嵩; 横田浩久; 今井洋
第78回応用物理学会秋季学術講演会, 06 Sep. 2017, 応用物理学会

フォトニック結晶ファイバ光減衰器の作製及び曲げによる減衰量調整　　　　　　　　　　　　　　　
佐野智彦; 横田浩久; 今井洋
第64回応用物理学会春季学術講演会, 16 Mar. 2017, 応用物理学会

ファイバ長許容誤差に優れたコリメータ用GI型フォトニック結晶ファイバの設計　　　　　　　　　　　　　　　
横田浩久; 若林美月; 樋口恵一; 今井 洋
電子情報通信学会 光ファイバ応用技術研究会, 20 Jan. 2017, 電子情報通信学会

カスケードファイバブラッググレーティングを用いた高感度放射線センシング　　　　　　　　　　　　　　　
若宮達也; 横田浩久; 今井 洋
平成28年度 電気学会東京支部茨城支所研究発表会, 17 Dec. 2016, 電気学会東京支部茨城支所

GI型フォトニック結晶ファイバの伝搬特性に対する空孔径対ピッチ比の影響　　　　　　　　　　　　　　　
横田浩久; 樋口恵一; 今井洋
電子情報通信学会2016年ソサイエティ大会, 22 Sep. 2016, 電子情報通信学会

ファイバグレーティングの反射特性に対する放射線照射の影響　　　　　　　　　　　　　　　
篠崎政人; 横田浩久; 今井洋
第75回応用物理学会秋季学術講演会, 18 Sep. 2014, 応用物理学会

CO2レーザ照射によるフォトニック結晶ファイバへの長周期グレーティング形成　　　　　　　　　　　　　　　
奈村晃平; 横田浩久; 今井洋
第75回応用物理学会秋季学術講演会, 18 Sep. 2014, 応用物理学会

ファイバ曲げを用いた偏波保持フォトニック結晶ファイバ可変光減衰器　　　　　　　　　　　　　　　
小林脩人; 横田浩久; 今井洋
第61回応用物理学会春季学術講演会, 17 Mar. 2014, 応用物理学会

偏波保持ファイバブラッググレーティングの特性に対する放射線照射の影響　　　　　　　　　　　　　　　
島袋洋太; 横田浩久; 今井洋
光ファイバ応用技術研究会, 28 Feb. 2014, 電子情報通信学会

空孔径制御を用いた偏波保持フォトニック結晶ファイバ光減衰器の作製　　　　　　　　　　　　　　　
横田浩久; 井上直哉; 小林脩人; 今井洋
電子情報通信学会・光ファイバ応用技術研究会, 25 Jan. 2013, 電子情報通信学会

テルライトファイバへのブラッググレーティング形成　　　　　　　　　　　　　　　
真野恭輔; 横田浩久; 今井洋
第59回応用物理学関係連合講演会, 17 Mar. 2012, 応用物理学会

グレーティング形成のための空孔径制御を行ったホールアシストファイバとその曲げ損失特性　　　　　　　　　　　　　　　
桐井裕史; 横田浩久; 今井洋
第59回応用物理学関係連合講演会, 17 Mar. 2012, 応用物理学会

空孔径制御を用いた偏波保持フォトニック結晶ファイバ光減衰器の作製　　　　　　　　　　　　　　　
井上直哉; 横田浩久; 今井洋
第59回応用物理学関係連合講演会, 17 Mar. 2012, 応用物理学会

テルライトファイバへの屈折率変調グレーティング形成　　　　　　　　　　　　　　　
横田浩久; 真野恭輔; 小林資昭; 今井洋; 佐々木豊
電子情報通信学会・光ファイバ応用技術研究会, 02 Mar. 2012, 電子情報通信学会

ホールアシストファイバグレーティング作製のための空孔径制御　　　　　　　　　　　　　　　
桐井裕史; 横田浩久; 今井洋
第58回応用物理学関係連合講演会, 09 Mar. 2011, 応用物理学会

CO2レーザ照射を用いて作製したテルライトファイバカプラにおける結合率向上の検討　　　　　　　　　　　　　　　
宮内裕貴; 横田浩久; 今井洋,森淳
第58回応用物理学関係連合講演会, 09 Mar. 2011, 応用物理学会

全光スイッチのためのテルライトファイバデバイス作製　　　　　　　　　　　　　　　
横田浩久; 宮内裕貴; 小林資昭; 今井洋; 佐々木豊; 森淳
電子情報通信学会2011年総合大会, 28 Feb. 2011, 電子情報通信学会

CO2レーザ照射を用いて作製したテルライトファイバカプラにおける結合率向上の検討　　　　　　　　　　　　　　　
宮内裕貴; 横田浩久; 今井洋,森淳
平成22年度電気学会東京支部茨城支所研究発表会, 14 Nov. 2010, 電気学会東京支部茨城支所

CO2レーザ照射による空孔径制御を用いたフォトニック結晶ファイバ光減衰器の作製　　　　　　　　　　　　　　　
横田浩久; 後田耕佑; 井上直哉; 今井洋; 佐々木豊
電子情報通信学会・光ファイバ応用技術研究会, 25 Oct. 2010, 電子情報通信学会

伝送用単一偏波フォトニック結晶ファイバの設計・試作　　　　　　　　　　　　　　　
市毛友也; 横田浩久; 今井洋; 木植秀之; 飛田英夫
電子情報通信学会2010年ソサイエティ大会, 15 Sep. 2010, 電子情報通信学会

ピコ秒パルスレーザ照射によるテルライトファイバグレーティングの作製および特性評価　　　　　　　　　　　　　　　
小林資昭; 横田浩久; 今井洋,森淳
第57回応用物理学関係連合講演会, 19 Mar. 2010, 応用物理学会

単一偏波ファイバ伝送系の理論的･実験的検討　　　　　　　　　　　　　　　
市毛友也; 横田浩久; 今井洋
第57回応用物理学関係連合講演会, 19 Mar. 2010, 応用物理学会

CO2レーザ照射による空孔制御を用いたフォトニック結晶ファイバカプラの結合特性調整　　　　　　　　　　　　　　　
横田浩久; 中島優; 市毛友也; 今井洋; 佐々木豊
電子情報通信学会・光ファイバ応用技術研究会, 30 Oct. 2009, 電子情報通信学会

空孔消失フォトニック結晶ファイバカプラにおける結合特性調整法に関する検討　　　　　　　　　　　　　　　
横田浩久; 中島優; 市毛友也; 今井洋; 佐々木豊
電子情報通信学会2009年ソサイエティ大会, 16 Sep. 2009, 電子情報通信学会

光ファイバリング共振器の出力光強度振動幅と非線形屈折率の依存性　　　　　　　　　　　　　　　
鈴木健仁; 時偉; 横田浩久; 今井洋
第70回応用物理学会学術講演会, 09 Sep. 2009, 応用物理学会

CO2レーザ照射を用いた空孔制御による非延伸型フォトニック結晶ファイバカプラの作製　　　　　　　　　　　　　　　
市毛友也; 原田大地; 横田浩久; 今井洋
第70回応用物理学会学術講演会, 09 Sep. 2009, 応用物理学会

ピコ秒パルスレーザ照射によるテルライトファイバグレーティングの作製　　　　　　　　　　　　　　　
小林資昭; 横田浩久; 今井洋,森淳
第70回応用物理学会学術講演会, 09 Sep. 2009, 応用物理学会

CO2レーザ照射法を用いたフォトニック結晶ファイバ光減衰器作製の研究　　　　　　　　　　　　　　　
後田耕佑; 高杉友之; 横田浩久; 佐々木豊
第56回応用物理学関係連合講演会, 02 Apr. 2009, 応用物理学会

CO2レーザの端面照射によるフォトニックバンドギャップファイバの空孔制御　　　　　　　　　　　　　　　
逆井和弘; 横田浩久; 佐々木豊
第56回応用物理学関係連合講演会, 02 Apr. 2009, 応用物理学会

フォトニック結晶ファイバとシングルモードファイバの融着型カプラ形成による接続　　　　　　　　　　　　　　　
横田浩久; 八嶋紘寛; 今井洋; 佐々木豊
電子情報通信学会・光ファイバ応用技術研究会, 21 Nov. 2008, 電子情報通信学会

フォトニック結晶ファイバとシングルモードファイバの融着型カプラ形成による接続　　　　　　　　　　　　　　　
横田浩久; 八嶋紘寛; 佐々木豊
電子情報通信学会2008年ソサイエティ大会, 17 Sep. 2008, 電子情報通信学会

全光スイッチ用テルライトファイバカプラの作製　　　　　　　　　　　　　　　
小林資昭; 中村祐介; 横田浩久; 佐々木豊; 森淳
電子情報通信学会2008年ソサイエティ大会, 17 Sep. 2008, 電子情報通信学会

CO2レーザ照射によるフォトニックバンドギャップファイバの空孔制御　　　　　　　　　　　　　　　
逆井和弘; 横田浩久; 佐々木豊
第69回応用物理学会学術講演会, 04 Sep. 2008, 応用物理学会

空孔径制御によるフォトニック結晶ファイバ光減衰器の減衰量制御　　　　　　　　　　　　　　　
後田耕佑; 横田浩久; 佐々木豊
第69回応用物理学会学術講演会, 04 Sep. 2008, 応用物理学会

単一偏波フォトニック結晶ファイバを用いた偏波保持フォトニック結晶ファイバカプラの研究　　　　　　　　　　　　　　　
中島優; 横田浩久; 佐々木豊
第69回応用物理学会学術講演会, 04 Sep. 2008, 応用物理学会

全光スイッチにおけるテルライトファイバカプラの作製と特性測定　　　　　　　　　　　　　　　
中村祐介; 小林資昭; 横田浩久; 佐々木豊; 森淳
第69回応用物理学会学術講演会, 04 Sep. 2008, 応用物理学会

光ファイバグレーティングカプラ型全光スイッチ　　　　　　　　　　　　　　　
横田浩久; 佐々木豊
第55回応用物理学関係連合講演会, 27 Mar. 2008, 応用物理学会, [Invited]

フォトニックバンドギャップファイバによる利得飽和の抑制　　　　　　　　　　　　　　　
逆井和弘; 宮原秀明; 横田浩久; 佐々木豊
第55回応用物理学関係連合講演会, 27 Mar. 2008, 応用物理学会

CO2レーザ照射を用いた空孔テーパ形成によるフォトニック結晶ファイバの接続損失低減　　　　　　　　　　　　　　　
八嶋紘寛; 横田浩久; 佐々木豊
第55回応用物理学関係連合講演会, 27 Mar. 2008, 応用物理学会

単一偏波フォトニック結晶ファイバを用いた偏波分離フォトニック結晶ファイバカプラの研究　　　　　　　　　　　　　　　
中島優; 川尻宏樹; 横田浩久; 佐々木豊
第55回応用物理学関係連合講演会, 27 Mar. 2008, 応用物理学会

スーパーストラクチャファイバグレーティングを用いた全光スイッチング　　　　　　　　　　　　　　　
福田成児; 横田浩久; 佐々木豊
第55回応用物理学関係連合講演会, 27 Mar. 2008, 応用物理学会

CO2レーザ照射によるフォトニック結晶ファイバ光減衰器の減衰量制御　　　　　　　　　　　　　　　
後田耕佑; 横田浩久; 佐々木豊
第55回応用物理学関係連合講演会, 27 Mar. 2007, 応用物理学会

The Institute of Electric and Electronics Engineers

The Japan Society of Applied Physics

The Institute of Electronics, Information, and Communication Engineers

Development of fiber collimator using a photonics crystal fiber with α-power air hole diameter distribution　　　　　　　　　　　　　　　
基盤研究(C)
Apr. 2016 - Mar. 2019

特許第6656668号, 特開2017-76097, 特願2015-205117, 光ファイバ、光ファイバケーブル及び光ファイバ接続方法
横田浩久、今井洋、樋口恵一