Silicon-on-Insulator Microring Add-Drop Filters With Free Spectral Ranges Over 30 nm

Purdue Univ., West Lafayette
Journal of Lightwave Technology (Impact Factor: 2.97). 02/2008; 26(2):228-236. DOI: 10.1109/JLT.2007.911098
Source: IEEE Xplore


We demonstrate highly compact optical add-drop filters based on silicon-on-insulator microring resonators. The microring resonators have a small radius of 2.5 mu m and a very large free spectral range ~ 32 nm at the 1.55 mu m communication band. The propagation loss in such small micoring resonators was experimentally determined and shown to be extremely important in designing microring add-drop filters with low add-drop crosstalk, low drop loss, and maximally flat drop passband. For box-like channel dropping responses, second-order optical add-drop filters with two coupled microring resonators are designed and demonstrated, and the simulation matches well with the experiment. Devices were patterned with electron-beam lithography. Two fabrication procedures utilizing different polarity of resists were introduced and compared, and the process with negative resist resulted in much smaller sidewall roughness of waveguides, thus reducing the propagation loss in microring resonators.

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Available from: Minghao Qi, Apr 04, 2015
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    • "High index contrast between core and cladding refractive indices results in a strong confinement of light even with a small bend radius. A large FSR (up to 32 nm) with a low level of bending loss has been achieved [3]. Polycrystalline silicon (poly Si) waveguides were proposed in [23] with radii of 3 ,4, and 5 μm and a FSR about 20-30 nm. "
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    ABSTRACT: In this paper, an overview of the optical ring resonators operation principle, fabrication and applications is presented. Emphasis was given for their add/drop functionality in Wavelength Division Multiplexing (WDM) networks. Ring resonator based Optical Add/Drop Multiplexer (OADMs) and filters are shown to be good candidates to realize Planar Lightwave Circuits (PLCs). They have a small 'real estate' requirement and are therefore potentially useful for large scale integrated optical circuits. However, like any other optical filters, ring resonator based OADMs are prone to crosstalk. The crosstalk suppression ratio (which is defined as the difference between the drop and through port responses at resonance) is shown to be highly affected by coupling coefficients. Controlling the coupling coefficients through careful design of the waveguide cross section, separation gap, and the length of the coupling region allows for increased crosstalk suppression ratio. Crosstalk in ring resonator based OADMs is modelled in this paper and an overview of the current state of knowledge about mitigating crosstalk is presented.
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    • "Add-drop filters using Microring Resonators (MRRs) have shown great promise for practical applications (Cai et al., 2000; Amiri I. S. et al., 2012a; I. S. Amiri et al., 2013a; I. S. Amiri et al., 2013b; I. S. Amiri and J. Ali, 2014a; I. S. Amiri et al., 2014f). Microrings have been studied more thoroughly due to their ease of fabrication and on chip structure (Popovíc et al., 2006; Xiao et al., 2008; Iraj Sadegh Amiri et al., 2014b; Sayed Ehsan Alavi et al., 2014). Wavelength selective optical add-drop filter is required for adding and dropping a particular Wavelength Division Multiplexing (WDM) channel at each subscriber node in the WDM based optical access networks. "
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    ABSTRACT: Add-drop ring resonator system is the fundamental building block of the optical transmission and communication systems. The loop of fiber optics as a microring resonator (MRR) with length of 750 μm is used to filter the input spectrum of Gaussian laser beam and generate the comb frequency of soliton pulses, where the transmission characteristics and group delay profile of the through and drop port output signals are presented.
    Full-text · Article · Jan 2014
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    • "In previous reports, the performance of single-channel microring add/drop filter has been improved significantly. The free spectral range (FSR) can be extended to more than 30 nm using ultra-small ring resonator [2], [3] or coupled rings with different radii (Vernier effect) [4], [5]. Box-like passband is also achieved by highorder coupled ring resonator filter [6], [7]. "
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    ABSTRACT: A four-channel integrated optical add/drop multiplexer is experimentally demonstrated on a silicon-on-insulator substrate. With the help of a parent-sub microring resonator structure, compact footprint, large free spectral range, and uniform channel spacing are achieved simultaneously. Through controlling the resonance matching between the parent and sub-rings through thermo-optic effect, each channel can be switched independently between the states of dropping and passing through. The thermal tuning efficiency is as high as 0.27 nm/mW. Typically, for dropping state, all four channels can be de-multiplexed to the drop ports with 2 dB drop loss, 18 dB through port extinction, and less than -20 dB channel crosstalk.
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