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A WDM/DWDM model for AWGs and Echelle Gratings

Perfect Chirped Grating Design

Epipprop allows you to implement a Perfect Chirped Grating (PCG), an innovative design which we reported in our recent publication [1]. This can be quickly added to a Rowland circle or applied to any arbitrary grating line. You can see below two different PCG designs created automatically by Epipprop for a Rowland mount and a user-defined sinusoidal grating line.

Perfect Chirped Grating Layout

PCG gratings based on (left) a Rowland circle mount created from the built-in template
and (right) a user-defined sinusoidal line

You can see below a comparison between a standard Rowland Grating and a PCG grating, both designs generated by EPIPPROP based on the same Rowland mount configuration (shown above on the left). The two devices share the same geometry, the only difference between the two being the position, size and orientation of their grating facets.

The standard Rowland Grating places the facets as a result of a projection from a flat blazed grating onto the Rowland circle mount while the PCG uses an algorithm to adjusts the position, size and angle of each individual facet effectively.  

Perfect Chirped Grating Spectra

Transmission spectra calculated by EPIPPROP (left) before applying PCG corrections
to a standard Rowland grating and (right) after applying PCG corrections

As can be seen in this example, changing the grating from a standard Rowland circle layout to a PCG layout improves the performance greatly, with the average insertion loss improving from -3.7dB (standard deviation of 0.5dB) for the Rowland circle design to -2dB (standard deviation of 0.5dB also) for the PCG. The crosstalk between channels is improved from -18dB to -55dB.

The PCG provides a performance comparable to that of a two stigmatic point grating, however the PCG is free for all to use which is unlike the stigmatic design which is patent protected.

We collaborated with CEA-LETI to design and fabricate PCGs in silicon photonics; you can find the article here [2].


[1] Lycett, R.J., Gallagher, D.F.G., Brulis, V.J., "Perfect Chirped Echelle Grating Wavelength Multiplexor: Design and Optimization", IEEE Photonics Journal, 5, 2, pp. 2400123-2400123 (2013) [PDF]

[2] Sciancalepore, C., Lycett, R.J., Dallery, J.A., Pauliac, S., Hassan, K., Harduin, J., Duprez, H., Weidenmueller, U., Gallagher, D.F.G., Menezo, S., Bakir, B.B., "Low-Crosstalk Fabrication-Insensitive Echelle Grating Demultiplexers on Silicon-on-Insulator", IEEE Photonics Technology Letters, 27, 5, pp. 494 - 497 (2014) [PDF]