OPTICAL PROPERTIES OF C-RGO and APPLICATION for TWO-MODE MICROFIBER SENSOR

Abstract

A highly sensitive relative humidity (RH) and temperature sensor in a living condition based on a two-mode microfiber knot resonator (TMM-KR) combining a cytop-reduced graphene oxide (C-rGO) catalyst is examined. The sensitivity of the proposed TMM-KR to the RH is favorably improved by mitigating the difference in effective refractive group indices between the HE11 and HE12 modes. The device is composed of two main optical features: two-mode microfiber (TMM, slow-varying term) and two-mode knot resonator (TM-KR, fast-varying term). In the TMM modal interferometer, two modes (HE11 and HE12) are excited and interfered in a non-adiabatically up-tapered region of the microfiber, resulting in an inline modal interferometer. After fabricating a TMM by non-adiabatically tapering a conventional single-mode fiber (SMF), I designed C-rGO-overlaid TMM as a polymer-overlaid optical sensor to evaluate the response and recovery times. By optimizing the diameter of the microfiber (∼4.2 m), the difference in effective refractive group indices between HE11 and HE12 is suppressed, resulting in an improved RH sensitivity of the proposed TMM-KR. By using the fast Fourier transform algorithm, optical transmission spectra of the TMM-KR are converted to spatial frequency spectra to precisely measure the concentration of RH. The absorption of RH in the proposed TMM-KR-based sensing probe effectively changes the resonant wavelength of the TMM modal interferometer and the spatial frequencies of the TMM-KR depending on the radial mode number (m) and the mode order (k). The effective group refractive index between fundamental and cladding modes, HE11 and HE12, respectively, of the TMM-KR, and the sensitivities of the proposed sensor remarkably enhanced to 0.603 nm/%, and -0.79 nm/oC, for RH and temperature, respectively. My calculated and experimental results demonstrated that the proposed micro-structure of the C-rGO-overlaid TMM-KR will provide optical properties that can be applied for the practical use of environmental sensing. The magnetic field sensors assisted by the development of microfiber technology have appealed to research interests in versatile applications in present detector and magnetic effect surveillance, including more benefits such as low loss, low cost, high sensitivity. The sensitivity of the two-parameter measurement of the TMM-KR was enhanced by approaching the dispersion turning point between HE11 and HE12 mode, which excited from the non-adiabatically formation in down-tapering transition were interfered producing to the TMM. My proposed sensor is forecasted to study essential applications in weak signal detection and high sensitivity. A TMM-KR with high sensitivity is investigated for ambient refractive index (ARI) measurement. The sensitivity of the proposed TMM-KR to the ambient index will be remarkably enhanced after mitigating the group index difference. The dual-parameter based sensing probe shown a presentation of ARI, with the experimental sensing proportions of 244 nm/RIU analogously to the fast-varying resonator, 1874 nm/RIU analogously to the slow-varying interferometer. Therefore, it is possible to successfully discriminate ARI and temperature sensitivities by measuring different frequency shifts of the proposed TMM-KR. |Cytop-reduced graphene oxide (C-rGO) 를 조합하여 이중모드 (two-mode) 마이크로 광섬유 매듭 공진기 (TMM-KR)를 기반으로 일반 환경에서 매우 민감한 상대 습도 (RH) 및 온도 센서를 연구하였습니다. 제안 된 TMM-KR의 RH에 대한 감도는 HE11과 HE12 모드 사이의 유효 굴절 그룹 지수의 차이를 이용하여 완화됩니다. 이 장치는 두 가지 주요 광학 성질로 구성됩니다. Two-mode 마이크로 광섬유 (TMM, 느리게 변하는 항) 및 two-mode 매듭 공진기 (TM-KR, 빠르게 변하는 항) TMM 모드 간섭계로, 마이크로 섬유의 테이퍼링 된 영역은 Two-mode (HE11 및 HE12) 가 여기되고 간섭되어 inline 모드 간섭계를 초래합니다. 기존의 단일 모드 광섬유 (SMF)를 테이퍼링하여 TMM을 제작한 후 C-rGO를 코팅한TMM을 광학 센서로 설계하여 응답 및 복구 시간을 평가했습니다. 마이크로 광섬유의 직경 (~ 4.2㎛)을 최적화함으로써, HE11과 HE12 사이의 유효 굴절률 차이가 억제되어 제안 된 TMM-KR의 RH 감도가 향상됩니다. 고속 푸리에 변환 알고리즘을 사용함으로써, TMM-KR의 광 투과 스펙트럼은 공간 주파수 스펙트럼으로 변환되어 RH의 농도를 정확하게 측정됩니다. 제안 된 TMM-KR 기반 감지 프로브에서 RH의 흡수는 방사형 모드 수 (m) 및 모드 차수 (k)에 따라 TMM 모달 간섭계의 공진 파장과 TMM-KR의 공간 주파수를 효과적으로 변경됩니다. TMM-KR의 기본 모드와 클래딩 모드, HE11 및 HE12 사이의 유효 그룹 굴절률과 제안 된 센서의 감도는 RH 및 온도에 대해 0.603 nm /% 및 -0.79 nm /℃로 현저하게 향상되었습니다. 이론계산 및 실험 결과는 각각 C-rGO-overlaid TMM-KR의 제안 된 미세 구조가 환경 감지의 실제 사용에 적용될 수 있는 광학 특성을 제공 할 것임을 입증했습니다. 마이크로 광섬유 기술의 개발을 지원하는 자기장 센서는 현재의 검출기 및 자기 영향 감시의 다양한 응용 분야에서 저손실, 저비용, 고감도와 같은 더 많은 이점을 포함한 연구 분야의 관심을 끌었습니다. 테이퍼링 구간에서 여기되어 TMM으로 간섭하여HE11과 HE12 모드 사이의 분산 전환점에 접근함으로써 TMM-KR의 두- 파라미터측정의 감도가 향상되었습니다. 제안된 센서는 약한 신호 감지 및 높은 감도의 필수 응용 분야를 연구 할 것으로 예상됩니다. 주변 굴절률 (ARI) 측정을 위해 감도가 높은 TMM-KR을 조사합니다. 그룹 인덱스 차이를 완화 한 후에 제안 된 TMM-KR의 주변 인덱스에 대한 감도가 현저하게 향상 될 것입니다. 이중 파라미터 기반 감지 프로브는 ARI의 표현을 보여 주었으며, 빠른 변동 공진기와 유사하게 실험 감지 비율이 244nm/RIU, 느린 변동 간섭계와 유사하게 1874nm/RIU입니다. 따라서 제안 된 TMM-KR의 다른 주파수 편이를 측정하여 ARI 및 온도 감도를 성공적으로 식별 할 수 있습니다.; A highly sensitive relative humidity (RH) and temperature sensor in a living condition based on a two-mode microfiber knot resonator (TMM-KR) combining a cytop-reduced graphene oxide (C-rGO) catalyst is examined. The sensitivity of the proposed TMM-KR to the RH is favorably improved by mitigating the difference in effective refractive group indices between the HE11 and HE12 modes. The device is composed of two main optical features: two-mode microfiber (TMM, slow-varying term) and two-mode knot resonator (TM-KR, fast-varying term). In the TMM modal interferometer, two modes (HE11 and HE12) are excited and interfered in a non-adiabatically up-tapered region of the microfiber, resulting in an inline modal interferometer. After fabricating a TMM by non-adiabatically tapering a conventional single-mode fiber (SMF), I designed C-rGO-overlaid TMM as a polymer-overlaid optical sensor to evaluate the response and recovery times. By optimizing the diameter of the microfiber (∼4.2 m), the difference in effective refractive group indices between HE11 and HE12 is suppressed, resulting in an improved RH sensitivity of the proposed TMM-KR. By using the fast Fourier transform algorithm, optical transmission spectra of the TMM-KR are converted to spatial frequency spectra to precisely measure the concentration of RH. The absorption of RH in the proposed TMM-KR-based sensing probe effectively changes the resonant wavelength of the TMM modal interferometer and the spatial frequencies of the TMM-KR depending on the radial mode number (m) and the mode order (k). The effective group refractive index between fundamental and cladding modes, HE11 and HE12, respectively, of the TMM-KR, and the sensitivities of the proposed sensor remarkably enhanced to 0.603 nm/%, and -0.79 nm/oC, for RH and temperature, respectively. My calculated and experimental results demonstrated that the proposed micro-structure of the C-rGO-overlaid TMM-KR will provide optical properties that can be applied for the practical use of environmental sensing. The magnetic field sensors assisted by the development of microfiber technology have appealed to research interests in versatile applications in present detector and magnetic effect surveillance, including more benefits such as low loss, low cost, high sensitivity. The sensitivity of the two-parameter measurement of the TMM-KR was enhanced by approaching the dispersion turning point between HE11 and HE12 mode, which excited from the non-adiabatically formation in down-tapering transition were interfered producing to the TMM. My proposed sensor is forecasted to study essential applications in weak signal detection and high sensitivity. A TMM-KR with high sensitivity is investigated for ambient refractive index (ARI) measurement. The sensitivity of the proposed TMM-KR to the ambient index will be remarkably enhanced after mitigating the group index difference. The dual-parameter based sensing probe shown a presentation of ARI, with the experimental sensing proportions of 244 nm/RIU analogously to the fast-varying resonator, 1874 nm/RIU analogously to the slow-varying interferometer. Therefore, it is possible to successfully discriminate ARI and temperature sensitivities by measuring different frequency shifts of the proposed TMM-KR.