A novel broad tunable bandwidth and narrow instantaneous line-width linear swept laser source using combined tunable filters working at 1,300 nm center wavelength is proposed.The combined filters consist of a fiber Fa...A novel broad tunable bandwidth and narrow instantaneous line-width linear swept laser source using combined tunable filters working at 1,300 nm center wavelength is proposed.The combined filters consist of a fiber FabryPerot tunable filter and a tunable filter based on diffractive grating with scanning polygon mirror.In contrast to traditional method using single tunable filter,the trade-off between bandwidth and instantaneous line-width is alleviated.Parallel implementation of two semiconductor optical amplifiers with different wavelength range is adopted in the laser resonator for broadband light amplification.The Fourier domain mode locking swept laser source with combined tunable filters offers broadband tunable range with narrow instantaneous line-width,which is especially benefiting for high-quality optical frequency domain imaging.The proposed Fourier domain mode locking swept laser source provides a tuning range of 160 nm with instantaneous line-width of about 0.01nm at sweeping rate of 15 kHz,a finesse of 16,000 is thus achieved.展开更多
Optical filters with different configurations based on cholesteric liquid crystals (CLCs) are designed. The central wavelength from CLCs can be tuned by the electric field or temperature. For the electric field tuni...Optical filters with different configurations based on cholesteric liquid crystals (CLCs) are designed. The central wavelength from CLCs can be tuned by the electric field or temperature. For the electric field tuning, the ITO is designed with circular patterns, which can make the tunable range 18 nm. For the temperature tuning, two-layer- CLC configurations are used. The experimental results indicate that a deepened or broadened bandgap from the CLC can be achieved by different handedness or concentrations of chiral dopants. The spectrum study is carried out.展开更多
A tunable single-passband microwave photonic filter is proposed and demonstrated, based on a laser diode (LD) array with multiple optical carriers and a Fabry-Perot (F-P) laser diode. Multiple optical carriers in conj...A tunable single-passband microwave photonic filter is proposed and demonstrated, based on a laser diode (LD) array with multiple optical carriers and a Fabry-Perot (F-P) laser diode. Multiple optical carriers in conjunction with the F-P LD will realize a filter with multiple passbands. By adjusting the wavelengths of the multiple optical carriers, multiple passbands are merged into a single passband with a broadened bandwidth. By varying the number of the optical carrier, the bandwidth can be adjusted. The central frequency can be tuned by adjusting the wavelength of the multiple optical carriers simultaneously. A single-passband filter implemented by two optical carriers is experimentally demonstrated.展开更多
In this paper we propose a two-pole varactor-tuned superconducting filter using coplanar waveguide (CPW) spiralin-spiral-out (SISO) resonators. Novel internal and external coupling structures are introduced to mee...In this paper we propose a two-pole varactor-tuned superconducting filter using coplanar waveguide (CPW) spiralin-spiral-out (SISO) resonators. Novel internal and external coupling structures are introduced to meet the requirements for a tunable filter with a constant absolute bandwidth. The fabricated device has a frequency tuning range of 14.4% at frequencies ranging from 274.1 MHz to 317.7 MHz, a 3-dB bandwidth of 5.14±0.06 MHz, and an insertion loss of 0.08 dB-0.70 dB. The simulated and measured results are in excellent agreement with each other.展开更多
Sensitive detection of acetylene(C_2H_2) is performed by absorption spectroscopy and wavelength modulation spectroscopy(WMS) based on Fiber Fabry–Perot tunable filter(FFP-TF) at 1530.32 nm. After being calibrat...Sensitive detection of acetylene(C_2H_2) is performed by absorption spectroscopy and wavelength modulation spectroscopy(WMS) based on Fiber Fabry–Perot tunable filter(FFP-TF) at 1530.32 nm. After being calibrated by Fiber Bragg Grating(FBG), FFP-TF is frequency-multiplexed and modulated at 20 Hz and 2.5 kHz respectively to achieve wavelength modulation. The linearity with 0.9907 fitting coefficient is obtained by measuring different concentrations in a 100 ppmv–400 ppmv range. Furthermore, the stability of the system is analyzed by detecting 50 ppmv and 100 ppmv standard gases for 2 h under room temperature and ambient pressure conditions respectively. The precision of 11 ppmv is achieved by calculating the standard deviation. Therefore, the measuring system of C_2H_2 detection can be applied in practical applications.展开更多
A compact tunable guided-mode resonant filter (GMRF) in the telecommunication region near the 1550 nm wave-length is proposed in this paper. Particle swarm optimization (PSO) is used to design the GMRF. The tunabi...A compact tunable guided-mode resonant filter (GMRF) in the telecommunication region near the 1550 nm wave-length is proposed in this paper. Particle swarm optimization (PSO) is used to design the GMRF. The tunability of the GMRF is achieved by an MEMS-based physical movement (in the horizontal or vertical direction) combined with an incident angle in a certain range. The results show that the resonant wavelength tuning of 110 nm (140mm) is obtained by horizontal movement of 168 nm (vertical movement of 435 nm) combined with an about 11° variation of incident angle.展开更多
In this paper we report for the first time the presence of bistability in an acoustic-optic tunable filter (AOTF) operating with ultrashort (2 ps) optical light pulses. The results for the study of bistability has sho...In this paper we report for the first time the presence of bistability in an acoustic-optic tunable filter (AOTF) operating with ultrashort (2 ps) optical light pulses. The results for the study of bistability has shown the dependence of the hysteresis curve with the product of the coupling constant (κ) by the length of the device (ξL) and the conversion power-coupling constant factor (G). The range of bistability varies significantly with both G and with κξL parameters. The variation of κξL directly increases the size of the range of bistability hysteresis while the increase in G causes the bistability to occur at low powers. The phenomenon of optical bistability (OB) is the object of increasing interest due to its possibilities for important device applications. A bistable device is a device with a capability to generate two different outputs for a given input and the physical requirements for this are an intensity-dependence refractive index and an optical feedback mechanism.展开更多
The size reduction of tunable micromachined filters is carried out for high-speed wavelength tuning. We fabricated micromachined filters having a miniature structure with an air gap of 300 run and a short cantilever o...The size reduction of tunable micromachined filters is carried out for high-speed wavelength tuning. We fabricated micromachined filters having a miniature structure with an air gap of 300 run and a short cantilever of 45 urn, exhibiting fast response of below 3 us.展开更多
A new kind of tunable optical filter is proposed for DWDM optical communication application. It is based on cascaded polarization interference filter (PIF). The period and bandpass width of each PIF are decided by its...A new kind of tunable optical filter is proposed for DWDM optical communication application. It is based on cascaded polarization interference filter (PIF). The period and bandpass width of each PIF are decided by its optical path difference between o-ray and e-ray (OPDOE). When their OPDOEs are proportionately designed, the tuning range and bandpass width depend on OPDOE in the first and the last PIF, respectively. The tuning range, bandpass width and crosstalk are independent each other. The crosstalk is related to the OPDOE ratios among PIFs and can be suppressed by designing the PIF's OPDOE. A set of OPDOE is suggested that are l1, 2 × l1, 22 ×l1, 23 ×l1, 24 ×l1, ..., 2N-4 × l1, 15 × 2N-7 ×l1, 10 × 2N-6 × l1 and 2N-2 ×l1 from the first to the last. This suggested OPDOEs can yield -50-dB crosstalk for any tuning range and bandpass width. The insert loss is less than 1 dB. As its loose alignment requirement, there is no limitation on cascaded PIF number. When 11 PIFs are cascaded, it can achieve 170-nm tuning range, -50-dB crosstalk, bandpass width applicable to 25-GHz channel spacing and 1 dB insert loss.展开更多
We report the experimental demonstration of an ultranarrow bandwidth atomic filter by optically induced polarization rotation in multilevel electromagnetically induced transparency systems in hot Rb vapor. With a coup...We report the experimental demonstration of an ultranarrow bandwidth atomic filter by optically induced polarization rotation in multilevel electromagnetically induced transparency systems in hot Rb vapor. With a coupling intensity of 2.3 W/cm^2, the filter shows a peak transmission of 33.2% and a bandwidth of 10 MHz. By altering the coupling frequency, a broad tuning range of several Doppler linewidths of the D1 line transitions of STRb atoms can be obtained. The presented atomic filter has useful features of ultranarrow bandwidth, and the operating frequency can be tuned resonance with the atomic transition. Such narrowband tunable atomic filter can be used as an efficient noise rejection tool in classical and quantum optical applications.展开更多
An ultracompact,bandwidth-tunable filter has been demonstrated using a silicon-on-insulator(SOI)wafer.The device is based on cascaded grating-assisted contra-directional couplers(GACDCs).It also involves the use of a ...An ultracompact,bandwidth-tunable filter has been demonstrated using a silicon-on-insulator(SOI)wafer.The device is based on cascaded grating-assisted contra-directional couplers(GACDCs).It also involves the use of a subwavelength grating(SWG)structure.By heating one of the heaters on GACDCs,a bandwidth tunability of~6 nm is achieved.Owing to the benefit of having a large coupling coefficient between SWG and strip waveguides,the length of the coupling region is only 100 pm.Moreover,the combination of the curved SWG and the tapered strip waveguides effectively suppresses the sidelobes.The filter possesses features of simultaneous wavelength tuning with no free spectral range(FSR)limitation.A maximum bandwidth of 10 nm was experimentally measured with a high out-of-band contrast of 25 dB.Similarly,the minimum bandwidth recorded is 4 nm with an out-of-band contrast of 15 dB.展开更多
We present the design,fabrication and characterization of hydraulically-tunable hyperchromatic lenses for two-dimensional(2D)spectrally-resolved spectral imaging.These hyperchromatic lenses,consisting of a positive di...We present the design,fabrication and characterization of hydraulically-tunable hyperchromatic lenses for two-dimensional(2D)spectrally-resolved spectral imaging.These hyperchromatic lenses,consisting of a positive diffractive lens and a tunable concave lens,are designed to have a large longitudinal chromatic dispersion and the images of different wavelengths from each other.2D objects of different wavelengths can consequently be imaged using the tunability of the lens system.Two hyperchromatic lens concepts are demonstrated and their spectral characteristics as well as their functionality in spectral imaging applications are shown.展开更多
A wide range (9.4nm) tuning of vertically coupled microring resonator filter was demonstrated utilizing a large TO coefficient of polymer. The power consumption was about 60m W and no degradation of filter response wa...A wide range (9.4nm) tuning of vertically coupled microring resonator filter was demonstrated utilizing a large TO coefficient of polymer. The power consumption was about 60m W and no degradation of filter response was observed.展开更多
Applicability of guided mode resonant structures to tunable optical filtering and sensing is demonstrated using nematic liquid crystals. As a sensor, a minimum refractive index detectivity of 10^-5 is demonstrated whi...Applicability of guided mode resonant structures to tunable optical filtering and sensing is demonstrated using nematic liquid crystals. As a sensor, a minimum refractive index detectivity of 10^-5 is demonstrated while as a tunable filter, tunability range of few tens of nanometers with 2-nm bandwidth is presented. The optimum design is achieved by maximizing the evanescent field region in the analyte which maximizes the overlap integral. The device can be operated in reflection or transmission modes at normal incidence. It can also be operated at a single wavelength by measuring the angular profile of the light beam.展开更多
We propose and demonstrate a pseudo Fabry–Pérot filter in the terahertz frequency range of 0.1–0.5 THz. It consists of alternative liquid crystal layers and metallic slats. Separate sharp resonant peaks are sho...We propose and demonstrate a pseudo Fabry–Pérot filter in the terahertz frequency range of 0.1–0.5 THz. It consists of alternative liquid crystal layers and metallic slats. Separate sharp resonant peaks are shown in the simulated transmission spectra, and their positions shift toward higher frequencies when the refractive index of liquid crystal decreases. The measured transmission spectra are consistent with corresponding simulations. Via thermally tuning the refractive index of the filled liquid crystal, the resonant transmission frequencies shift accordingly. The work supplies a novel design for tunable terahertz filters, which would play important roles in terahertz imaging, sensing, high speed communication, and security applications.展开更多
A narrowband tunable antireflection optical filter is proposed and numerically studied. The structure is a metasurface based on plasmonic nanoparticles on an electro-optic film in a three-layer configuration of metald...A narrowband tunable antireflection optical filter is proposed and numerically studied. The structure is a metasurface based on plasmonic nanoparticles on an electro-optic film in a three-layer configuration of metaldielectric-metal(MDM) in the visible near-infrared range. By tuning the voltage and thus tuning the refractive index of the dielectric Li Nb O_3, one can shift the wavelength of minimum reflection as desired. The parameters of gold nanoparticles and other elements used for the filter design and refractive index of the dielectric are obtained by the finite-element method(FEM). An analytical theory is presented to explain the FEM simulation results, and they agree well with each other. It is found that the frequency of the plasmonic resonance wave on the metasurface should be equal to that of the Fabry–Perot resonator formed by the MDM to have a good filtering property. Theoretical spectra obtained by FEM simulation show that the structure has extensive potential for the design of tunable narrow-band filters for modulators, displayers, and color extraction for imaging.展开更多
Induced acoustic wave to bare fiber through various types of horn are examined. The center wavelength and extinction ratio of the notch filter are dynamically tunable and dependent on the RF signals.
A novel acousto-optic tunable filter (AOTF) using a hollow optical fiber (HOF) is proposed. Its broadband rejection over 100nm was observed and high polarization dependence as a polarization switch is discussed.
An automatic visible spectrometer based on a non-collinear acousto-optic tunable filter (AOTF) is constructed for high-speed spectrometry. Its spectral filtering characteristics, such as relationships between the radi...An automatic visible spectrometer based on a non-collinear acousto-optic tunable filter (AOTF) is constructed for high-speed spectrometry. Its spectral filtering characteristics, such as relationships between the radio-frequency (RF) driving frequency and the output central wavelength, the output bandwidth and the central wavelength, its typical spectral point spread function (PSF), and so on, are studied systematically. The preliminary measurement results of AOTF spectrometer show that it is a solid-state, high-speed, easily controllable by computer-programming, rugged and compact spectroscopic device in comparison with a conventional grating spectrometer, and has the potential for widespread spectrometric applications.展开更多
We report a wavelength and power monitoring system based on a scanning MEMS filter as wavelength discriminator and a near threshold-biased Fabry-Perot diode laser as wavelength reference. This system is capable of mon...We report a wavelength and power monitoring system based on a scanning MEMS filter as wavelength discriminator and a near threshold-biased Fabry-Perot diode laser as wavelength reference. This system is capable of monitoring 250 channels of DWDM signal at 25 GHz ITU Grid with an error of less than ±8 pm.展开更多
基金supported by Natural Science Foundation of China(60978037,60878057).
文摘A novel broad tunable bandwidth and narrow instantaneous line-width linear swept laser source using combined tunable filters working at 1,300 nm center wavelength is proposed.The combined filters consist of a fiber FabryPerot tunable filter and a tunable filter based on diffractive grating with scanning polygon mirror.In contrast to traditional method using single tunable filter,the trade-off between bandwidth and instantaneous line-width is alleviated.Parallel implementation of two semiconductor optical amplifiers with different wavelength range is adopted in the laser resonator for broadband light amplification.The Fourier domain mode locking swept laser source with combined tunable filters offers broadband tunable range with narrow instantaneous line-width,which is especially benefiting for high-quality optical frequency domain imaging.The proposed Fourier domain mode locking swept laser source provides a tuning range of 160 nm with instantaneous line-width of about 0.01nm at sweeping rate of 15 kHz,a finesse of 16,000 is thus achieved.
基金Supported by the National Natural Science Foundation of China under Grant Nos 61107059,61308052 and 61077047the Fundamental Research Funds for the Central Universitiesthe 111 Project of the Harbin Engineering University under Grant No B13015
文摘Optical filters with different configurations based on cholesteric liquid crystals (CLCs) are designed. The central wavelength from CLCs can be tuned by the electric field or temperature. For the electric field tuning, the ITO is designed with circular patterns, which can make the tunable range 18 nm. For the temperature tuning, two-layer- CLC configurations are used. The experimental results indicate that a deepened or broadened bandgap from the CLC can be achieved by different handedness or concentrations of chiral dopants. The spectrum study is carried out.
基金Supported by the National Natural Science Foundation of China under Grant Nos 61302026,61275067 and 61575034the Jiangsu Natural Science Foundation under Grant No BK2012432
文摘A tunable single-passband microwave photonic filter is proposed and demonstrated, based on a laser diode (LD) array with multiple optical carriers and a Fabry-Perot (F-P) laser diode. Multiple optical carriers in conjunction with the F-P LD will realize a filter with multiple passbands. By adjusting the wavelengths of the multiple optical carriers, multiple passbands are merged into a single passband with a broadened bandwidth. By varying the number of the optical carrier, the bandwidth can be adjusted. The central frequency can be tuned by adjusting the wavelength of the multiple optical carriers simultaneously. A single-passband filter implemented by two optical carriers is experimentally demonstrated.
基金supported by the National Natural Science Foundation of China(Grant No.61371009)the National High Technology Research and Development Program of China(Grant No.2014AA032703)
文摘In this paper we propose a two-pole varactor-tuned superconducting filter using coplanar waveguide (CPW) spiralin-spiral-out (SISO) resonators. Novel internal and external coupling structures are introduced to meet the requirements for a tunable filter with a constant absolute bandwidth. The fabricated device has a frequency tuning range of 14.4% at frequencies ranging from 274.1 MHz to 317.7 MHz, a 3-dB bandwidth of 5.14±0.06 MHz, and an insertion loss of 0.08 dB-0.70 dB. The simulated and measured results are in excellent agreement with each other.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61172047 and 61071025)
文摘Sensitive detection of acetylene(C_2H_2) is performed by absorption spectroscopy and wavelength modulation spectroscopy(WMS) based on Fiber Fabry–Perot tunable filter(FFP-TF) at 1530.32 nm. After being calibrated by Fiber Bragg Grating(FBG), FFP-TF is frequency-multiplexed and modulated at 20 Hz and 2.5 kHz respectively to achieve wavelength modulation. The linearity with 0.9907 fitting coefficient is obtained by measuring different concentrations in a 100 ppmv–400 ppmv range. Furthermore, the stability of the system is analyzed by detecting 50 ppmv and 100 ppmv standard gases for 2 h under room temperature and ambient pressure conditions respectively. The precision of 11 ppmv is achieved by calculating the standard deviation. Therefore, the measuring system of C_2H_2 detection can be applied in practical applications.
基金Project supported by the National High-Tech Research and Development Program of China(Grant No.2011 AA050518)
文摘A compact tunable guided-mode resonant filter (GMRF) in the telecommunication region near the 1550 nm wave-length is proposed in this paper. Particle swarm optimization (PSO) is used to design the GMRF. The tunability of the GMRF is achieved by an MEMS-based physical movement (in the horizontal or vertical direction) combined with an incident angle in a certain range. The results show that the resonant wavelength tuning of 110 nm (140mm) is obtained by horizontal movement of 168 nm (vertical movement of 435 nm) combined with an about 11° variation of incident angle.
基金CAPES(Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior),CNPq(Conselho Nacional de Desenvolvimento Cientifico e Tecnologico),FINEP(Financiadora de Estudos e Projetos),FUNCAP(Fundacao Cearense de Amparo a Pesquisa)for the financial support and CENTEC(Instituto Centro de Ensino Tecnologico).
文摘In this paper we report for the first time the presence of bistability in an acoustic-optic tunable filter (AOTF) operating with ultrashort (2 ps) optical light pulses. The results for the study of bistability has shown the dependence of the hysteresis curve with the product of the coupling constant (κ) by the length of the device (ξL) and the conversion power-coupling constant factor (G). The range of bistability varies significantly with both G and with κξL parameters. The variation of κξL directly increases the size of the range of bistability hysteresis while the increase in G causes the bistability to occur at low powers. The phenomenon of optical bistability (OB) is the object of increasing interest due to its possibilities for important device applications. A bistable device is a device with a capability to generate two different outputs for a given input and the physical requirements for this are an intensity-dependence refractive index and an optical feedback mechanism.
文摘The size reduction of tunable micromachined filters is carried out for high-speed wavelength tuning. We fabricated micromachined filters having a miniature structure with an air gap of 300 run and a short cantilever of 45 urn, exhibiting fast response of below 3 us.
文摘A new kind of tunable optical filter is proposed for DWDM optical communication application. It is based on cascaded polarization interference filter (PIF). The period and bandpass width of each PIF are decided by its optical path difference between o-ray and e-ray (OPDOE). When their OPDOEs are proportionately designed, the tuning range and bandpass width depend on OPDOE in the first and the last PIF, respectively. The tuning range, bandpass width and crosstalk are independent each other. The crosstalk is related to the OPDOE ratios among PIFs and can be suppressed by designing the PIF's OPDOE. A set of OPDOE is suggested that are l1, 2 × l1, 22 ×l1, 23 ×l1, 24 ×l1, ..., 2N-4 × l1, 15 × 2N-7 ×l1, 10 × 2N-6 × l1 and 2N-2 ×l1 from the first to the last. This suggested OPDOEs can yield -50-dB crosstalk for any tuning range and bandpass width. The insert loss is less than 1 dB. As its loose alignment requirement, there is no limitation on cascaded PIF number. When 11 PIFs are cascaded, it can achieve 170-nm tuning range, -50-dB crosstalk, bandpass width applicable to 25-GHz channel spacing and 1 dB insert loss.
基金supported by the National Basic Research Program of China(No.2006CB921203)the National Natural Science Foundation of China(No.11174327)+1 种基金the Foundation of Wuhan National Laboratory for Optoelectronics(No.P080002)the support of the Hundred Talent Program by the Chinese Academy of Sciences
文摘We report the experimental demonstration of an ultranarrow bandwidth atomic filter by optically induced polarization rotation in multilevel electromagnetically induced transparency systems in hot Rb vapor. With a coupling intensity of 2.3 W/cm^2, the filter shows a peak transmission of 33.2% and a bandwidth of 10 MHz. By altering the coupling frequency, a broad tuning range of several Doppler linewidths of the D1 line transitions of STRb atoms can be obtained. The presented atomic filter has useful features of ultranarrow bandwidth, and the operating frequency can be tuned resonance with the atomic transition. Such narrowband tunable atomic filter can be used as an efficient noise rejection tool in classical and quantum optical applications.
基金This work was supported in part by the National Key R&D Program of China(No.2019YFB2203101)in part by the National Natural Science Foundation of China(Grant Nos.61805137 and 61835008)+2 种基金in part by the Natural Science Foundation of Shanghai,China(No.19ZR1475400)Shanghai Sailing Program(No.18YF1411900)Open Project Program of Wuhan National Laboratory for Optoelectronics(No.2018WNLOKF012).
文摘An ultracompact,bandwidth-tunable filter has been demonstrated using a silicon-on-insulator(SOI)wafer.The device is based on cascaded grating-assisted contra-directional couplers(GACDCs).It also involves the use of a subwavelength grating(SWG)structure.By heating one of the heaters on GACDCs,a bandwidth tunability of~6 nm is achieved.Owing to the benefit of having a large coupling coefficient between SWG and strip waveguides,the length of the coupling region is only 100 pm.Moreover,the combination of the curved SWG and the tapered strip waveguides effectively suppresses the sidelobes.The filter possesses features of simultaneous wavelength tuning with no free spectral range(FSR)limitation.A maximum bandwidth of 10 nm was experimentally measured with a high out-of-band contrast of 25 dB.Similarly,the minimum bandwidth recorded is 4 nm with an out-of-band contrast of 15 dB.
基金This work was funded by the German Federal Ministry of Education and Research.
文摘We present the design,fabrication and characterization of hydraulically-tunable hyperchromatic lenses for two-dimensional(2D)spectrally-resolved spectral imaging.These hyperchromatic lenses,consisting of a positive diffractive lens and a tunable concave lens,are designed to have a large longitudinal chromatic dispersion and the images of different wavelengths from each other.2D objects of different wavelengths can consequently be imaged using the tunability of the lens system.Two hyperchromatic lens concepts are demonstrated and their spectral characteristics as well as their functionality in spectral imaging applications are shown.
文摘A wide range (9.4nm) tuning of vertically coupled microring resonator filter was demonstrated utilizing a large TO coefficient of polymer. The power consumption was about 60m W and no degradation of filter response was observed.
基金supported by the Ministry of Scienceunder Tashtiot Project
文摘Applicability of guided mode resonant structures to tunable optical filtering and sensing is demonstrated using nematic liquid crystals. As a sensor, a minimum refractive index detectivity of 10^-5 is demonstrated while as a tunable filter, tunability range of few tens of nanometers with 2-nm bandwidth is presented. The optimum design is achieved by maximizing the evanescent field region in the analyte which maximizes the overlap integral. The device can be operated in reflection or transmission modes at normal incidence. It can also be operated at a single wavelength by measuring the angular profile of the light beam.
基金supported by the National Natural Science Foundation of China(Nos.11304151,61490714,61435008,and 61575093)the Ph.D.Programs Foundation of the Ministry of Education of China(No.20120091120020)the Fundamental Research Funds for the Central Universities(Nos.021314380020 and 021314380023)
文摘We propose and demonstrate a pseudo Fabry–Pérot filter in the terahertz frequency range of 0.1–0.5 THz. It consists of alternative liquid crystal layers and metallic slats. Separate sharp resonant peaks are shown in the simulated transmission spectra, and their positions shift toward higher frequencies when the refractive index of liquid crystal decreases. The measured transmission spectra are consistent with corresponding simulations. Via thermally tuning the refractive index of the filled liquid crystal, the resonant transmission frequencies shift accordingly. The work supplies a novel design for tunable terahertz filters, which would play important roles in terahertz imaging, sensing, high speed communication, and security applications.
基金National Natural Science Foundation of China(NSFC)(61275043,61605128,61307048)
文摘A narrowband tunable antireflection optical filter is proposed and numerically studied. The structure is a metasurface based on plasmonic nanoparticles on an electro-optic film in a three-layer configuration of metaldielectric-metal(MDM) in the visible near-infrared range. By tuning the voltage and thus tuning the refractive index of the dielectric Li Nb O_3, one can shift the wavelength of minimum reflection as desired. The parameters of gold nanoparticles and other elements used for the filter design and refractive index of the dielectric are obtained by the finite-element method(FEM). An analytical theory is presented to explain the FEM simulation results, and they agree well with each other. It is found that the frequency of the plasmonic resonance wave on the metasurface should be equal to that of the Fabry–Perot resonator formed by the MDM to have a good filtering property. Theoretical spectra obtained by FEM simulation show that the structure has extensive potential for the design of tunable narrow-band filters for modulators, displayers, and color extraction for imaging.
文摘Induced acoustic wave to bare fiber through various types of horn are examined. The center wavelength and extinction ratio of the notch filter are dynamically tunable and dependent on the RF signals.
文摘A novel acousto-optic tunable filter (AOTF) using a hollow optical fiber (HOF) is proposed. Its broadband rejection over 100nm was observed and high polarization dependence as a polarization switch is discussed.
基金This work was supported by the National Natural Sciences Foundation of China under Grant No. 60007002.
文摘An automatic visible spectrometer based on a non-collinear acousto-optic tunable filter (AOTF) is constructed for high-speed spectrometry. Its spectral filtering characteristics, such as relationships between the radio-frequency (RF) driving frequency and the output central wavelength, the output bandwidth and the central wavelength, its typical spectral point spread function (PSF), and so on, are studied systematically. The preliminary measurement results of AOTF spectrometer show that it is a solid-state, high-speed, easily controllable by computer-programming, rugged and compact spectroscopic device in comparison with a conventional grating spectrometer, and has the potential for widespread spectrometric applications.
文摘We report a wavelength and power monitoring system based on a scanning MEMS filter as wavelength discriminator and a near threshold-biased Fabry-Perot diode laser as wavelength reference. This system is capable of monitoring 250 channels of DWDM signal at 25 GHz ITU Grid with an error of less than ±8 pm.