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SEM images of the fabricated device. (a) Top view of the photonic-crystal structure with two cavities side-coupled to one waveguide. (b) Magnified view of the microcavity . The circle approximately corresponds to the size of the focal spot of the pumping laser. The actual heated region however is substantially larger due to thermal conductance.
Graphical illustration of results computed with coupled mode theory. In plotting the curves, we assume two intrinsically lossless resonators with the same coupling rate to a waveguide as follows: and . The resonance frequencies are detuned at an arbitrary small number, , and here we let . We also assume that the waveguide has a linear dispersion relation . (a) EIT-like transmission spectrum when . (b) Flat-top reflection filter when .
Experimental transmission spectra (blue solid line) and theoretical fits (red dashed line) of the photonic-crystal system of Fig. 1, with a pump laser beam incident on the waveguide near the midpoint between the two microcavities. Curves (a)–(d) correspond to different pump powers. In particular, curves (a), (b), and (d) exhibit a line shape analogous to EIT. Curve (c) exhibits a flat-top reflection response.
The parameters used in Eqs. (1)–(3) to fit the experimental curves in Fig. 3. The second column is the power of the laser beam that is delivered to the sample. In the remaining columns the subscripts A or B label the two resonators. are the resonant wavelengths. and are the intrinsic quality factors. and are the waveguide-resonator coupling quality factors. is a parameter that determines the waveguide propagation phase , where is calculated by the finite-difference time-domain simulation.
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