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This paper reports a novel architecture for the design of dense wavelength-division multiplexing interleavers based on planar echelle gratings. Double astigmatic point design of the echelle grating is discussed. The important and inherent limitation of aberrations associated with the echelle grating has been eliminated by the introduction of aberration free elliptical facets. A mechanism for compensating the variations of the refractive index with wavelength is also described. The theoretical analysis was used to design and manufacture remarkably low footprint 50/100 and 100/200 GHz interleavers in silica-on-silicon with the waveguide refractive index contrast of 0.62%. The comparison between the theoretical and experimental results shows an excellent agreement. The fabricated devices based on the proposed approach showed low nonuniformity in insertion loss, high dynamic range, and precise channel periodicity over the entire C band. [ABSTRACT FROM PUBLISHER]

A new approach for eliminating aberration effects through introduction of elliptical grating facets in optical comb filters is presented. Simulation results show remarkable improvements of comb filter performance for aberration-free elliptical facets compared to traditional flat facet designs. The proposed theory was validated through design and fabrication of 100-GHz-period planar silica-on-silicon comb filters for use in multiwavelength optical sources. Multimode interference structures were used to achieve both flat-top and Gaussian spectral comb filter responses. All devices showed high extinction ratio, low nonuniformity in insertion loss, and high degree of passband shape control. [ABSTRACT FROM PUBLISHER]

A novel design of a silicon-on-insulator (SOI) filter for passive optical network applications is described. The SOI filter comprises a monolithically integrated planar reflective grating and a multistage Mach-Zehnder interferometer. The fabricated device showed low insertion losses and high optical isolation. To the best of our knowledge, this letter describes the first demonstration of an SOI circuit comprising monolithically integrated planar reflective grating and cascaded Mach-Zehnder interferometer [ABSTRACT FROM PUBLISHER]

We demonstrate that planar reflective gratings can be used to design a cascaded microspectrometer that is capable of processing optical signals with different spectroscopic signatures. The filter is based on a double-grating additive dispersion architecture. The first planar grating is used to multiplex single-mode signals from the 1310-nm band into the fiber and weakly demultiplex the band around 1550 nm from the fiber. The second grating doubles the dispersion of the first grating, improves the rejection of stray light, and produces a box-like spectral response around 1550 nm at the output. The device was fabricated using a standard silica-on-silicon process with a refractive index contrast of 0.82% and has a remarkably small footprint of only 0.29 cm2. Experimental measurements of the device show Gaussian-shaped spectral response at 1310 nm with a 1-dB bandwidth of 21 nm and box-like transmission at 1550 nm with a bandwidth of 33 nm. The insertion losses for the two channels were measured to be -4.7 and -5.8 dB, respectively. To the best of our knowledge, this is the first demonstration of an integrated planar lightwave circuit that is based on multiple reflective gratings. Applications of the microspectrometer for biophotonics, spectroscopy, and telecommunications are discussed. [ABSTRACT FROM PUBLISHER]