Tailoring the spectral response of add/drop single and multiple resonators in silicon-on-insulator

Abstract

Channel dropping waveguide filters based on single and multiple resonators in silicon-on-insulator (SOI) technology are of great interest due to their compactness and high wavelength selectivity, which is a desirable feature for photonic modulators, detectors, and other optically integrated components in telecommunication systems, in particular for wavelength division multiplexing (WDM) systems. Particular advantage of these filters is that they are capable of producing relatively large free spectral range (FSR) as well as narrow 3-dB bandwidth of the filter resonances. Herein we report experimental results and discuss the possibility of designing mono-mode and (nearly) polarization independent SOI ring and racetrack resonators with the FSR in excess of 30 nm.OCIS codes: 130.0130, 250.0250, 230.7370, 260.3060, 260.5430. doi: 10.3788/COL20090704.0291. Miniaturization of photonic devices has been significantly intensified in the last decade in an attempt to improve a footprint and performance of integrated optical components. Silicon-on-insulator (SOI) has emerged as a promising material choice for various integrated optoelectronic devices [1] . It is attractive for complex optical systems as the cost can be significantly reduced due to the compatibility with complementary metal oxide semiconductor (CMOS) technology [2] . It also has a high refractive index contrast between the core and the cladding, which is an important property for good confinement of light and efficient guiding and coupling in sub-micron waveguides. However, for those devices that are intended to be part of broadband optical networks, for example multiplexers and de-multiplexers, it is desirable to demonstrate a high selectivity and a tunable response. Thus, it is necessary to provide wavelength selective elements with the ability to filter input data streams producing a large free spectral range (FSR), a small full-width at half-maximum (FWHM), and a high quality factor (Q), and all conditions set by communication standards. Owing to the generic and adaptable operation, ring-resonator-types of filters in SOI are often considered as candidates to meet these demands.In silicon photonics, there is a particular focus on two waveguide architectures upon which the devices are typically built. Rib waveguides have proven to be particularly useful regarding polarization properties [3] . Single-mode and polarization independent (PI) resonators on rib waveguides have already been experimentally demonstrated [4] , but their FSR is usually small for applications in optical networks. On the other hand, strip waveguides, or photonic wires, allow small bend radii [5,6] , which in turn results in the improved FSR. They have to be rather small in cross-section to prevent higher-order modes (HOMs) from propagation [7] , and they exhibit polarization dependence and loss issues.In majority of applications, single-mode devices are required in order to minimize dispersion caused by multiple spatial modes which, in turn, allows for more information to be transmi...

High performance Vernier racetrack resonators

“…However, the interstitial peak suppression (IPS) (defined as the difference between a major resonance peak and the highest interstitial peak) is important since, if it is too small, the series-coupled ring resonator will not be appropriate for a practical WDM system due to interchannel cross talk. To date, the published experimental results of seriescoupled ring resonators exhibiting the Vernier effect, using silicon-on-insulator (SOI) strip waveguides, show the extension of the FSR [3][4][5][6][7]; however, the largest IPS was only 11 dB [4]. Here, we show the experimental dependency of the IPS and 3 dB bandwidth (BW) on the inter-ring gap distance, compare with models, and show substantially improved performance.…”

“…There will be major resonance peaks found in the spectrum when an integer multiple of the FSR of each individual ring resonator of the series is equal to the FSR of the series-coupled ring resonator system, and all other peaks will be suppressed between two consecutive major peaks [1][2][3][4][5][6][7]. Therefore, ideally the FSR of the series-coupled system can be considerably extended compared to the FSR of the individual ring resonators in the series, thus enabling the use of larger resonators having lower bending losses [1,2].…”

“…The more attractive method is to utilize the Vernier effect by using series-coupled ring resonators in which each of the resonators in the series has a different total length and, therefore, different FSR from the other resonators in the series [1][2][3][4][5][6][7]. There will be major resonance peaks found in the spectrum when an integer multiple of the FSR of each individual ring resonator of the series is equal to the FSR of the series-coupled ring resonator system, and all other peaks will be suppressed between two consecutive major peaks [1][2][3][4][5][6][7].…”

Design of a high-modulation-depth, low-energy silicon modulator based on coupling tuning in a resonance-split microring

“…Recently, optical switching was proposed [23] and experimentally demonstrated [24] based on coupled ring resonators with Vernier effect, which has been investigated on different material platforms, including SOI [25][26][27], polymer [28], and III-V compound semiconductors [29,30]. Furthermore, mutual mode coupling in single-ring resonators was explored [31] and utilized for many applications, such as fast light in an overcoupled region [32], continuously tunable slow-to fastlight in double-waveguide coupled resonators [33], dense wavelength conversion and multicasting [34], and optical upconversion in radio-over-fiber systems [35].…”

Optimisation Design of Coupling Region Based on SOI Micro-Ring Resonator

“…Thus, the larger sized optical cavity (R = 642 μm) and higher-Q value (up to five times the power) is produced without any surface treatment. This study is helpful for the achievement of optical cavities with a large size and high-Q value, which not only provides an important basis for the research of integrated optical gyroscopes, but is also propitious to their applications in the filters [6][7][8], modulators [9], biological sensing detection [10,11] and other related fields.…”