Vertically coupled glass microring resonator channel dropping filters

Micro-Optical Resonators for Microlasers and Integrated Optoelectronics

“…Silica glass is a widely used resonator material, which combines the advantage of a very low intrinsic material loss, a large transparency window, and compatibility with standard fibre-optic technologies, e.g., efficient coupling to optical fibres (Sandoghdar, 1996;Gorodetsky, 1996;Laine, 2001;Ilchenko, 2001). The silica-on-silicon technology that involves growing silica layers on silicon substrates is one the most widely used technologies to fabricate planar microresonator devices (Eldada, 2001;Polman, 2004), although microring resonators made of compound glasses (Ta 2 O 5 -SiO 2 ) have also been demonstrated (Little, 1999). A glass platform is relatively inexpensive, and as the index contrasts are smaller than for semiconductors, larger-size singlemode resonators can be fabricated by using cheaper lithographic techniques.…”

“…5b) filters that can combine or separate different wavelengths of light carrying different information are essential components for controlling and manipulating light in optical transmission systems. High-Q microdisks/microrings evanescently coupled to bus waveguides have been extensively explored for WDM channel dropping due to their ability to select a single channel with a very narrow linewidth (Hagness, 1997;Little, 1997Little, , 1999Chin, 1999;Boriskina, 1999;. To compromise between the requirements for a narrow channel linewidth, structure compactness, and wide FSR, the radii of the microresonators used in filters are usually in between 5 and 30 micron, resulting in filters with a FSR of 20-30 nm.…”

“…Recently proposed micro-toroidal resonators (Ilchenko, 2001;Vahala, 2003;Polman, 2004) not only demonstrate very high WG-mode Qfactors approaching those of microspheres but also enable reduction of WGmode volume, increase of resonator FSR, and on-chip integration with other components. Circular high-index-contrast microring and microdisk resonators based on planar waveguide technology with diameters as small as 1-10 μm are able to support strongly-confined WG modes with typical Q-factors of 10 4 -10 5 and are widely used as microlaser cavities Baba, 1997Baba, , 1999Cao, 2000;Zhang, 1996) and add/drop filters for WDM networks (Hagness, 1997;Little, 1997Little, , 1999Chin, 1999). Recently, record Q-factors have been demonstrated in wedge-edge microdisk resonators (Q in excess of 1 million, and in polished crystalline microcavities (Q>10 10 , Savchenkov, 2004).…”

“…MBE is characterized by low growth temperatures and low growth rates and thus enables producing high-precision epitaxial structures with monolayer control. Other wafer growth techniques include chemical vapour deposition (Foord, 1997) of reactant gases broken down at high temperatures, which can be used to deposit GaN, GaInAsP, Si, SiO 2 , Si 3 N 4 , and polymer materials; sputter (or physical vapour) deposition, which is a process of controlled deposition of energetic ionized particles of SiO 2 , Si 3 N 4 , metals, and alloys (Little, 1999); and wafer bonding, or fusing of two materials (e.g., Si to glass, Si to Si, III-V semiconductors to SiN or SiO 2 ) at the atomic level (Tishinin, 1999). A resonator structure is then imaged onto a wafer through a multi-step lithography process.…”

“…Coupling to microsphere (Serpenguzel, 1995;Spillane, 2002) and microtoroid resonators through tapered fibres has several distinct advantages such as the built-in coupler alignment, relatively simple fabrication, possible on-chip integration, and control of the coupling efficiency by the change of the fibre thickness. However, integrated, waferfabricated microresonators are usually coupled into a photonic circuit through either planar (rib) waveguides (Hagness, 1997;Little, 1997Little, , 1999Chin, 1999;Zhang, 1996; or PC waveguides (Noda, 2000).…”