Study on Transmission and Output Polarization Characteristics of a First-Order Lyot-Type Fiber Comb Filter Using Polarization-Diversity Loop

Songhyun Jo,Youngho Kim,Yong Wook Lee IEEE 2015 IEEE photonics journal Vol.7 No.4

<P>A first-order Lyot-type fiber comb filter was fabricated by incorporating a polarization-diversity loop structure composed of a polarization beam splitter, two half-wave plates (HWPs), and two polarization-maintaining fiber (PMF) segments. One of the two PMF segments was two times longer than the other, and they were concatenated with a 600 offset between their principal axes. The transmission spectra and output polarization characteristics of the filter were theoretically predicted and experimentally verified. By proper control of the two HWPs, first-order transmission spectra could be obtained, including flat-top and lossy flat-top band modes, and the interleaving operation of the respective spectrum could be also achieved. This flat-top band mode spectrum showed a higher attenuation rate at the cutoff level, in comparison with that of the Solc-type filter. In particular, it was revealed that the output state of polarization of the filter was a periodical function of wavelength and that the evolution period was different, according to transmission band modes. With the help of a linear output polarizer, the specific portion of a passband could be passed or rejected by controlling input polarization. It was also theoretically predicted that the fine tuning of the passband center was possible within a specific wavelength range.</P>

Polarization-Independent Multiwavelength-Switchable Filter Based on Polarization Beam Splitter and Fiber Coupler

이용욱 대한전기학회 2009 Journal of Electrical Engineering & Technology Vol.4 No.3

A polarization-independent multiwavelength-switchable fiber filter is proposed based on a polarization beam splitter and fiber coupler, which can function as a polarization-independent transmission or reflection-type interleaving filter. The proposed filter consists of a polarization beam splitter and a Sagnac birefringence loop composed of a 50:50 coupler, high birefringent fibers, and two quarter-wave plates. In the proposed filter, a transmission-type interleaver with a channel isolation > 18 dB or a reflection-type one with a channel isolation of ~3 dB, whose channel spacing and switching dis-placement were 0.8 and 0.4 nm in common, respectively, could be obtained. A channel interleaving op-eration could be performed by the proper control of waveplates within the Sagnac birefringence loop.

Polarization-Independent Multiwavelength-Switchable Filter Based on Polarization Beam Splitter and Fiber Coupler

Yong Wook Lee 대한전기학회 2009 Journal of Electrical Engineering & Technology Vol.4 No.3

A polarization-independent multiwavelength-switchable fiber filter is proposed based on a polarization beam splitter and fiber coupler, which can function as a polarization-independent transmission or reflection-type interleaving filter. The proposed filter consists of a polarization beam splitter and a Sagnac birefringence loop composed of a 50:50 coupler, high birefringent fibers, and two quarter-wave plates. In the proposed filter, a transmission-type interleaver with a channel isolation >18 ㏈ or a reflection-type one with a channel isolation of ~3 ㏈, whose channel spacing and switching displacement were 0.8 and 0.4 nm in common, respectively, could be obtained. A channel interleaving operation could be performed by the proper control of waveplates within the Sagnac birefringence loop.

편광 상이 루프 구조 기반 Lyot형 고차 광섬유 빗살 필터

조송현(Song-Hyun Jo),김영호(Young-Ho Kim),이용욱(Yong-Wook Lee) 한국조명·전기설비학회 2013 조명·전기설비학회논문지 Vol.27 No.12

In this paper, we propose a Lyot-type optical fiber comb filter based on a polarization-diversity loop structure (PDLS), which has flat-top pass bands and multiwavelength switching capability. Generally, the PDLS can remove the dependency of the filter on input polarization. The proposed filter is composed of a polarization beam splitter, two half-wave plates (HWPs), and two polarization-maintaining fiber loops concatenated with a 60° offset between their principal axes. By controlling two HWPs, it can operate in a flat-top band mode or a lossy flat-top band mode with an inherent insertion loss of ∼3.49dB. In particular, flat-top bands can be interleaved in both modes, which cannot be realized in a Lyot-Sagnac comb filter based on a fiber coupler. Compared with Solc-type high-order comb filters with the same order, the proposed filter shows sharper transition between pass and stop bands.

Eight Inch Wafer-Scale Flexible Polarization-Dependent Color Filters with Ag-TiO₂ Composite Nanowires

Zhao, Zhi-Jun,Lee, Minpyo,Kang, Hyeokjung,Hwang, SoonHyoung,Jeon, Sohee,Park, Namkyoo,Park, Sang-Hu,Jeong, Jun-Ho American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.10

<P>In this study, 8 in. wafer-scale flexible polarization-dependent color filters with Ag-TiO<SUB>2</SUB> composite nanowires have been fabricated using nanoimprint and E-beam evaporation. The filters change their color via a simple rotation of the polarizer. In addition, the color of the filter can be controlled by altering the thickness of the Ag and TiO<SUB>2</SUB> nanowires deposited on the polymer patterns. Polarization-dependent color filters were realized by selective inhibition of transmission using the plasmonic resonance at the insulator/metal/insulator nanostructure interface, which occurs at particular wavelengths for the transverse magnetic polarizations. Special colors, including purple, blue, green, yellow, and pink, could be obtained with high transmission beyond 65% by varying the thickness of the deposited Ag and TiO<SUB>2</SUB> nanowires on the periodic polymer pattern under transverse magnetic polarization. In addition, a continuous color change was achieved by varying the polarization angle. Last, numerical simulations were implemented in comparison with the experimental results, and the mechanism was explained. We believe that this simple and cost-effective method can be applied to processes such as anticounterfeiting and holographic imaging as well as to color displays.</P> [FIG OMISSION]</BR>

편광상이 고리 구조 기반 Lyot형 고차 광섬유 빗살 필터의 출력 편광 분석에 관한 연구

조송현(Songhyun Jo),이용욱(Yong Wook Lee) 한국조명·전기설비학회 2015 조명·전기설비학회논문지 Vol.29 No.10

In this paper, we investigated the output polarization of a Lyot-type optical fiber comb filter based on a polarization-diversity loop structure. It was found that the output state of polarization (SOP) of the filter made a wavelength-dependent evolution, and the spectral periods of the output SOP variation in flat-top and lossy flat-top band modes were the channel separation of the filter and its half, respectively. For a certain input SOP, the filter could pass or reject specific spectral sections by adding and controlling an output analyzer. In particular, it was theoretically anticipated that the filter with the output polarizer could provide the fine continuous tuning of its pass band center in a wavelength range corresponding to the ±9.5% of channel spacing(0.8㎚) when the input SOP was properly adjusted. It is expected that this tuning function can be effectively applied to suppress unwanted spectral portions in modulated optical signals.

Polarization-Independent Multiwavelength-Switchable Filter Based on Polarization Beam Splitter and Fiber Coupler

Lee, Yong-Wook The Korean Institute of Electrical Engineers 2009 Journal of Electrical Engineering & Technology Vol.4 No.3

A polarization-independent multiwavelength-switchable fiber filter is proposed based on a polarization beam splitter and fiber coupler, which can function as a polarization-independent transmission or reflection-type interleaving filter. The proposed filter consists of a polarization beam splitter and a Sagnac birefringence loop composed of a 50:50 coupler, high birefringent fibers, and two quarter-wave plates. In the proposed filter, a transmission-type interleaver with a channel isolation > 18 dB or a reflection-type one with a channel isolation of ${\sim}3$ dB, whose channel spacing and switching displacement were 0.8 and 0.4 nm in common, respectively, could be obtained. A channel interleaving operation could be performed by the proper control of waveplates within the Sagnac birefringence loop.

연속 파장 조절 가능한 편광상이 고리 기반 협대역 복굴절 필터

김도경,이용욱 한국조명.전기설비학회 2019 조명·전기설비학회논문지 Vol.33 No.7

Here, we present a continuously wavelength-controllable narrowband birefringence filter utilizing polarization-diversity loop. A polarization beam splitter, three half-wave plates, two quarter-wave plates, and two polarization-maintaining fiber with equal length were used to configure the filter. First, the orientation angle sets of the five waveplates that can induce an extra phase difference from 0 to 360° to the narrowband transmittance function derived using Jones matrix formulation were theoretically found. Then, among the found waveplate angle sets, transmission spectra were calculated for eight waveplate angle sets(Sets I-VIII) that can add extra phase differences from 0 to 315° with a step of 45° to the narrowband transmittance function. In the calculated transmission spectra, when the waveplate angle set was sequentially switched from Set I to Set VIII, the wavelength of the narrowband transmission spectrum could be shifted by 0.1nm. In particular, the theoretically predicted wavelength controllability of the filter was experimentally demonstrated.

단일 모드 광섬유의 복굴절이 편광상이 배치구조 기반 고차 광섬유 빗살 필터의 출력 스펙트럼에 미치는 영향에 대한 고찰

김영호(Young-Ho Kim),이용욱(Yong-Wook Lee) 한국조명·전기설비학회 2012 조명·전기설비학회논문지 Vol.26 No.6

In this paper, we investigated possible optical parameters causing deviation of experimentally observed output spectra from theoretically predicted results in a high-order fiber comb filter based on a polarization-diversity loop configuration. They include wavelength dependency of half-wave plates (HWPs) inserted in the filter for wavelength switching and the modal birefringence of single-mode fibers (SMFs) with which optical components comprising the filter are connected. In order to consider the effect of the modal birefringence of the SMF on a filter performance, it is modeled as a low birefringence fiber with an arbitrary orientation angle and birefringence. It is found from the simulation results that the modal birefringence of SMFs strongly affects the spectral characteristics of the filter and decreases the extinction ratio of the filter, compared with the wavelength dependency of HWPs. In particular, it is also confirmed that the spectral deviation and asymmetric distortions of side-lobes in narrow band transmission spectra result mainly from the modal birefringence of SMFs.

Proposal and Analysis of Wavelength-Switchable Optical Fiber Filter Based on a Solc Type

Minwook Kim,정재훈 한국광학회 2008 Current Optics and Photonics Vol.12 No.3

This paper proposes a new polarization-independent Sagnac birefringence loop structure-based multiwavelength-periodic filter and presents measurements and analysis of its spectrum. The filter can be used in several schemes by adjusting the orientation angles of two quarter waveplates and the operating characteristics in the reflection type are analyzed including dispersion and polarization mode dispersion at each principal axis. This filter has polarization-independent spectra but a polarization-dependent dispersion, consequently polarization mode dispersion whose values changes with operating schemes.