Fig. 1. Present silicon photonic spectrometer with multiple customized wavelength bands: (a) 3D view; (b) top view; and (c) the principle.

Fig. 2. (a) Triangular corrugation MWG wideband filter. (b) Rectangular corrugation MWG wideband filter. (c)–(e) Longitudinal apodization for the triangular corrugation MWG. (f)–(h) Longitudinal apodization for the rectangular corrugation MWG. (i) Mode (de)multiplexer based on an adiabatic dual-core taper; and (j) bent coupling based narrowband filter.

Fig. 3. Calculated wavelength dependence of the designed dual-core adiabatic taper for (a) the 1310 nm wavelength band, (b) the 1550 nm wavelength band, and (c) the 1930 nm wavelength band. Calculated spectral responses of the transmissions at the drop ports for the designed MWGs at the channels of (d) 1310 nm, (e) 1560/1570 nm, and (f) 1930 nm. Calculated spectral responses for the drop/through ports of designed microring resonators at the channels of (g) 1310 nm, (h) 1560/1570 nm, and (i) 1930 nm.

Fig. 4. Microscope images of the fabricated multiband customized spectrometer.

Fig. 5. Measured spectral responses for the four channels: (a) 1310 nm, (b) 1560 nm/1570 nm, and (c) 1930 nm.

Fig. 6. Measured spectral responses at the through/drop ports of the narrowband filters for the four channels: (a) 1310 nm, (b) 1560 nm, (c) 1570 nm, and (d) 1930 nm. The spectral response of the narrowband filters when applying different heating power for the four channels: (e) 1310 nm, (f) 1560 nm, (g) 1570 nm, and (h) 1930 nm. The resonance wavelength as the heating power Ph increases for the four channels: (i) 1310 nm, (j) 1560 nm, (k) 1570 nm, and (l) 1930 nm.

Fig. 7. Calibrated wavelength power map. The arrow indicates the peak wavelength λi dropped by the i-th cascaded wideband filter when the heating power Ph is 10 mW.

Fig. 8. Retrieved spectrum for a given spectrum with a single peak when using the present on-chip spectrometer as well as a commercial OSA: (a) 1309.65 nm, (b) 1557 nm, (c) 1569 nm, and (d) 1931.94 nm. Normalized retrieved spectrum with double-peak input around 1550 nm: (e) (1559.58, 1559.66) nm, (f) (1557.58, 1562.58) nm, (g) (1569.65, 1569.73) nm, and (h) (1567.58, 1572.58) nm. (i) Measured results for the ultrawide window complex spectrum ranging from 1307 nm to 1935 nm.