Demonstration of a distributed etched diffraction grating demultiplexer

Integrated Microspectrometer with Elliptical Bragg Mirror Enhanced Diffraction Grating on Silicon on Insulator

“…Finally the efficiency of the diffraction grating itself could not be estimated at this stage due to the several possible sources of loss in the whole spectrometer previously mentioned, but is expected to be high from the precise FDTD estimation. For comparison, other CDG spectrometers have an average efficiency of −3.2 dB, with a range from −5.0 to −1.6 dB, as claimed, ,− ,,,,,− and have an average channel uniformity (over a band equivalent to 30 nm at 1550 mn) of 0.9 dB, with a range from 1.5 to 0.2 dB. ,− ,,,,,− This places the present spectrometer within the state of the art for efficiency and at a high level for uniformity. Moreover its efficiency can still be improved, whereas other CDG devices are limited by the design.…”

“…Considering these advantages for the CDG, it is also possible at the same time to alleviate the disadvantages of using a classical metallic mirror. This metallic mirror can be replaced by other solutions, of which Bragg mirrors present a higher efficiency, ,, but the efficiency of the diffraction grating itself can be further increased, up to levels of −0.004 dB (99.9%), as we have shown . This is obtained with the use of an elliptical Bragg mirror extending over the diffraction grating, which preserves the blazing condition and focusing and redirects nearly all of the optical power into a single diffracted order.…”