• Photonics Research
  • Vol. 9, Issue 4, 04000596 (2021)
Yanmei Cao1, Ezgi Sahin1、2, Ju Won Choi1, Peng Xing1, George F. R. Chen1, D. K. T. Ng3, Benjamin J. Eggleton4、5, and Dawn T. H. Tan1、*
Author Affiliations
  • 1Photonics Devices and Systems Group, Singapore University of Technology and Design, 8 Somapah Road, Singapore 487372, Singapore
  • 2Current address: Photonic Systems Laboratory (PHOSL), Ecole Polytechnique Fédérale de Lausanne, STI-IEL, Station 11, CH-1015 Lausanne, Switzerland
  • 3Institute of Microelectronics, A*STAR, 2 Fusionopolis Way, #08-02, Innovis Tower, Singapore 138634, Singapore
  • 4Institute of Photonics and Optical Science, School of Physics, The University of Sydney, Sydney, New South Wales 2006, Australia
  • 5The University of Sydney Nano Institute (Sydney Nano), The University of Sydney, Sydney, New South Wales 2006, Australia
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    3D schematic of the ultra-silicon-rich nitride (USRN) device showing the CMBG and USRN waveguide parameters, where Lapod is the apodization length, Λ is the grating pitch, and G1 and Gapod are the distances between the pillars and the USRN waveguide. The insets show the principle of our thermo-optic tuning method.
    Fig. 1. 3D schematic of the ultra-silicon-rich nitride (USRN) device showing the CMBG and USRN waveguide parameters, where Lapod is the apodization length, Λ is the grating pitch, and G1 and Gapod are the distances between the pillars and the USRN waveguide. The insets show the principle of our thermo-optic tuning method.
    (a) Group index (ng) and second-order dispersion (β2) coefficient of the CMBG at different temperatures located at 1536 nm. (b) Third-order (β3) and fourth-order dispersion (β4) coefficients of the CMBG at different temperatures located at 1536 nm.
    Fig. 2. (a) Group index (ng) and second-order dispersion (β2) coefficient of the CMBG at different temperatures located at 1536 nm. (b) Third-order (β3) and fourth-order dispersion (β4) coefficients of the CMBG at different temperatures located at 1536 nm.
    (a) Simulated spectral broadening at different temperatures at a fixed pulse wavelength of 1536 nm. Simulated and measured (b) −30 dB and (c) −20 dB bandwidth of the output spectrum as a function of temperature.
    Fig. 3. (a) Simulated spectral broadening at different temperatures at a fixed pulse wavelength of 1536 nm. Simulated and measured (b) 30  dB and (c) 20  dB bandwidth of the output spectrum as a function of temperature.
    (a) Simulated spectral profiles at the end of the CMBG. (b) Simulated temporal profiles as a function of temperature at the end of the CMBG. (c) Simulated temporal FWHM at the end of the CMBG stage for each temperature point.
    Fig. 4. (a) Simulated spectral profiles at the end of the CMBG. (b) Simulated temporal profiles as a function of temperature at the end of the CMBG. (c) Simulated temporal FWHM at the end of the CMBG stage for each temperature point.
    (a) Schematic of the experimental setup, where blue lines denote the polarization maintaining (PM) fibers, with DUT, device under test; OSA, optical spectrum analyzer; TLF, tapered lensed fiber; TC, temperature controller; OA, optical attenuator; FFL, femtosecond fiber laser. (b) Measured spectral broadening at different temperatures and the input pulse at a fixed input wavelength of 1536 nm. (c) Measured spectral bandwidth at −30 dB level as a function of temperature.
    Fig. 5. (a) Schematic of the experimental setup, where blue lines denote the polarization maintaining (PM) fibers, with DUT, device under test; OSA, optical spectrum analyzer; TLF, tapered lensed fiber; TC, temperature controller; OA, optical attenuator; FFL, femtosecond fiber laser. (b) Measured spectral broadening at different temperatures and the input pulse at a fixed input wavelength of 1536 nm. (c) Measured spectral bandwidth at 30  dB level as a function of temperature.
    (a) Measured temperature-dependent stopband of a characteristic cladding modulated Bragg grating with a stopband centered at 1557 nm at 25°C. (b) Measured transmission spectra of USRN grating used in the spectral broadening measurement showing the stopband of 1553 nm at 25°C. (c) The measured Bragg wavelength at different temperatures. (d) The measured refractive index of USRN at different temperatures.
    Fig. 6. (a) Measured temperature-dependent stopband of a characteristic cladding modulated Bragg grating with a stopband centered at 1557 nm at 25°C. (b) Measured transmission spectra of USRN grating used in the spectral broadening measurement showing the stopband of 1553 nm at 25°C. (c) The measured Bragg wavelength at different temperatures. (d) The measured refractive index of USRN at different temperatures.
    MethodPower Loss30 dB Bandwidth RangeRefs.
    Acousto-optic tunable filter17 dB<2  nm[3]a
    Acousto-optic tunable coupler based on an acousto-optic filter and a taper fiberNot mentioned<2  nm[4]a
    Strain-induced chirped fiber Bragg grating and erbium-ytterbium co-doped fibersNot mentioned<1  nm[5]a
    Integrated electroabsorption modulatorNot mentioned<1  nm[6]a
    Optical band-pass filter based on thermal-tuning microring-MZI structure15 dB<4  nm[7]a
    Compact microring resonators using thermally tuned interferometric couplersNot mentioned<1  nm[8]a
    Add-drop filter using a voltage-tuned microtoroidal resonatorNot mentioned<1  nm[9]a
    Using temperature tunable USRN grating6.35 dB69106  nmThis work
    Table 1. Comparison of Various Approaches toward Tuning of Laser Pulse Bandwidth
    Copy Citation Text
    Yanmei Cao, Ezgi Sahin, Ju Won Choi, Peng Xing, George F. R. Chen, D. K. T. Ng, Benjamin J. Eggleton, Dawn T. H. Tan. Thermo-optically tunable spectral broadening in a nonlinear ultra-silicon-rich nitride Bragg grating[J]. Photonics Research, 2021, 9(4): 04000596
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    Category: Integrated Optics
    Received: Sep. 28, 2020
    Accepted: Feb. 3, 2021
    Posted: Feb. 5, 2021
    Published Online: Apr. 6, 2021
    The Author Email: Dawn T. H. Tan (dawn_tan@sutd.edu.sg)