Development of a Band-stop Filter Based on a Straight Waveguide Coupled with a Single Loop
A straight waveguide and single-ring coupled resonator with CdS core and Ag cladding is designed based on the coupled field theory,the micro-ring resonance theory,and COSMOL software.In the range of 1 540-1 580 nm of working wavelength,the transmittance and coupling strength of the coupler are analyzed by finite element method.It is found that the distance H between the straight waveguide and the single ring is changed when the incident wavelength is 1.55 μm and other setting parameters are unchanged.Under the condition of resonance,when the distance H is 200 nm,the optical energy in the micro-ring resonator will be significantly enhanced,and the coupling intensity in the micro-ring is the largest,so the transmittance is the smallest,which can be used as a band-stop filter in the ring cavity.When H is 200 nm,in the case of other setting parameters unchanged but only the wavelength changed,it is found that the coupling strength between straight waveguide and micro-ring reaches the maximum at the wavelength of 1.560 3 μm.Finally,the curves of transmittance and absorption based on COSMOL simulation are compared with the MATLAB results.It is confirmed that the coupling distance H between the straight waveguide and the micro-ring is 200 nm,the coupling strength and absorption at the wavelength of 1.560 3 μm are close to 1,which indicates that this microstructure can be used as a band-stop filter of the ring cavity.
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