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Research · Publication & note

September 21, 2012 September 9, 2026

A fully integrated high-Q Whispering-Gallery Wedge Resonator - Notes

Research publication featured image
Journal article
Fernando Ramiro-Manzano, Nikola Prtljaga, Lorenzo Pavesi, Georg Pucker and Mher Ghulinyan
Optics Express
Volume 20
Issue 20
Pages 22934-22942
2012
DOI · 10.1364/OE.20.022934 View article at Optica Optics Express journal
Published abstract
Microresonator devices which possess ultra-high quality factors are essential for fundamental investigations and applications. Microsphere and microtoroid resonators support remarkably high Q values at optical frequencies, while planarity constraints preclude their integration into functional lightwave circuits. Conventional semiconductor processing can also be used to realize ultra-high-Q planar wedge resonators, but their full integration with side-coupled dielectric waveguides remains an issue. Here we show the full monolithic integration of a wedge-resonator and vertically coupled waveguide system on a silicon chip. Because the cavity and waveguide lie in different planes, the shallow-angle wedge can be realized while the waveguide remains intact, allowing arbitrary coupling strength to be engineered. Precise size control and robustness against post-processing make this system a promising platform for industrial-scale integration of ultra-high-Q devices into planar lightwave chips.
How to cite
Figures
Figure 1. Evanescent-field coupling schemes in integrated photonics.
Figure 1. Evanescent-field coupling schemes in integrated photonics.
Figure 2. Integrated wedge and conventional microdisk resonators vertically coupled to bus waveguides on a silicon chip.
Figure 2. Fully integrated wedge and conventional microdisk resonators with vertical coupling to bus waveguides on a silicon chip.
Figure 3. Process flow for vertically coupled wedge-resonator and waveguide systems.
Figure 3. Process flow used to fabricate vertically coupled wedge-resonator and waveguide systems.
Figure 4. Optical characterisation of wedge resonators.
Figure 4. Optical characterisation of wedge resonators, including transmission spectra and resonance analysis.
Complete six-panel numerical analysis of wedge resonator mode confinement and intensity profiles
Figure 5. Numerical analysis of the resonator field intensity.
Figures reproduced from F. Ramiro-Manzano et al., Optics Express 20, 22934-22942 (2012), DOI: 10.1364/OE.20.022934. © 2012 Optical Society of America. This open-access article is reused for non-commercial purposes with attribution and a working link to the published article, in accordance with the Optica Publishing Group author and end-user reuse policy.

Article access and reuse

© 2012 Optical Society of America. The article was published in Optics Express. The figures shown on this author’s personal website are accompanied by the complete bibliographic attribution; reuse remains governed by the article’s access terms and Optica Publishing Group copyright policy.

Related publications

Connections within F. Ramiro-Manzano's publication record, selected from shared research topics and evidence reviewed in the source papers.

Featured image for Microring Resonators and Silicon Photonics
Journal article
MRS Advances 1(48), 3281-3293 (2016)
Microring Resonators and Silicon Photonics
F. Ramiro-Manzano, S. Biasi, M. Bernard, M. Mancinelli, T. Chalyan, F. Turri, M. Ghulinyan, M. Borghi, A. Samusenko, D. Gandolfi, R. Guider, A. Trenti, P.-É. Larré, L. Pasquardini, N. Prtljaga, S. Manna, I. Carusotto, G. Pucker and L. Pavesi

What the related paper adds

This later paper extends the research direction developed in A fully integrated high-Q Whispering-Gallery Wedge Resonator. This review explains microring resonators as reusable building blocks of silicon photonics. It brings together coupling, filtering, sensing, nonlinear response and integration choices, providing a compact technical map for understanding why changes in geometry and access waveguide produce very different device functions.

What this paper adds to the related work

This paper provides an earlier basis for the later development reported in Microring Resonators and Silicon Photonics. This paper applies vertical integration to a shallow-angle wedge resonator and preserves both the high-quality cavity edge and the underlying waveguide. The result is a monolithic device with controllable coupling strength, robust alignment and a fabrication route compatible with stable planar photonic circuits.

Vertically coupled resonator cross-section, simulated radial mode positions and optical measurement setup
Journal article
Journal of Lightwave Technology 34(23), 5385-5390 (2016)
Wavelength Dependence of a Vertically Coupled Resonator-Waveguide System
F. Turri, F. Ramiro-Manzano, I. Carusotto, M. Ghulinyan, G. Pucker and L. Pavesi

What the related paper adds

This later paper extends the research direction developed in A fully integrated high-Q Whispering-Gallery Wedge Resonator. This study extends the oscillatory vertical-coupling model across wavelength. It demonstrates simultaneous access to visible and infrared resonances and explains how the long interaction region broadens the useful coupling band, an advantage for multiwavelength and frequency-conversion experiments.

What this paper adds to the related work

This paper provides an earlier basis for the later development reported in Wavelength Dependence of a Vertically Coupled Resonator-Waveguide System. This paper applies vertical integration to a shallow-angle wedge resonator and preserves both the high-quality cavity edge and the underlying waveguide. The result is a monolithic device with controllable coupling strength, robust alignment and a fabrication route compatible with stable planar photonic circuits.

Silicon Microresonators
Book chapter
New Horizons in Nanoscience and Engineering · Chapter 2 · pp. 37-86 (2015)
Silicon Microresonators: How to Give a New Twist to Silicon Photonics
M. Borghi, D. Gandolfi, M. Ghulinyan, R. Guider, M. Mancinelli, G. Pucker, F. Ramiro-Manzano, F. Turri and L. Pavesi

What the related paper adds

This later paper extends the research direction developed in A fully integrated high-Q Whispering-Gallery Wedge Resonator. This chapter follows silicon microresonators from individual components to complex photonic functions. It connects interferometric switching, coupled-resonator chaos, vertical coupling, nonlinear bistability, biosensing and optomechanics, showing how one device family can support both fundamental experiments and scalable circuits.

What this paper adds to the related work

This paper provides an earlier basis for the later development reported in Silicon Microresonators: How to Give a New Twist to Silicon Photonics. This paper applies vertical integration to a shallow-angle wedge resonator and preserves both the high-quality cavity edge and the underlying waveguide. The result is a monolithic device with controllable coupling strength, robust alignment and a fabrication route compatible with stable planar photonic circuits.

Complete four-panel composition showing the experimental apparatus, resonance shift, bulk refractive-index response and measured sensitivity of disk and wedge resonators
Journal article
Sensors 15(3), 4796-4809 (2015)
Role of Edge Inclination in an Optical Microdisk Resonator for Label-Free Sensing
D. Gandolfi, F. J. Aparicio Rebollo, F. Ramiro Manzano, M. Ghulinyan, G. Pucker and L. Pavesi

What the related paper adds

This later paper extends the research direction developed in A fully integrated high-Q Whispering-Gallery Wedge Resonator. This paper turns the vertically coupled wedge platform into a refractometric sensor and quantifies how the sloped edge changes performance. Experiments and simulations show that thickness and sidewall inclination jointly balance quality factor against environmental field overlap, providing concrete design rules for high figures of merit.

What this paper adds to the related work

This paper provides an earlier basis for the later development reported in Role of Edge Inclination in an Optical Microdisk Resonator for Label-Free Sensing. This paper applies vertical integration to a shallow-angle wedge resonator and preserves both the high-quality cavity edge and the underlying waveguide. The result is a monolithic device with controllable coupling strength, robust alignment and a fabrication route compatible with stable planar photonic circuits.

Proceedings of SPIE journal identification graphic
Proceedings paper
Proc. SPIE 8767, 876704 (2013)
Monolithic integration of high-Q wedge resonators with vertically coupled waveguides
F. Ramiro-Manzano, N. Prtljaga, L. Pavesi, G. Pucker and M. Ghulinyan

What the related paper adds

This later paper extends the research direction developed in A fully integrated high-Q Whispering-Gallery Wedge Resonator. This work presents the integration strategy as a practical device platform, joining high-Q wedge resonators to vertically coupled waveguides on silicon. It emphasizes wafer-scale compatibility, stable optical access and the ability to engineer the coupling gap independently from the resonator profile.

What this paper adds to the related work

This paper provides an earlier basis for the later development reported in Monolithic integration of high-Q wedge resonators with vertically coupled waveguides. This paper applies vertical integration to a shallow-angle wedge resonator and preserves both the high-quality cavity edge and the underlying waveguide. The result is a monolithic device with controllable coupling strength, robust alignment and a fabrication route compatible with stable planar photonic circuits.

Proceedings of SPIE journal identification graphic
Proceedings paper
Proc. SPIE 8600, 86001G (2013)
Silicon-based monolithically integrated whispering-gallery mode resonators
F. Ramiro-Manzano, M. Ghulinyan, N. Prtljaga, G. Pucker and L. Pavesi

What the related paper adds

This later paper extends the research direction developed in A fully integrated high-Q Whispering-Gallery Wedge Resonator. This contribution develops the monolithically integrated whispering-gallery platform around accurate waveguide planarization and separate fabrication planes. It demonstrates how buried guides can access free-standing resonators while retaining design freedom in geometry and materials, a key step towards scalable optomechanical and metrological devices.

What this paper adds to the related work

This paper provides an earlier basis for the later development reported in Silicon-based monolithically integrated whispering-gallery mode resonators. This paper applies vertical integration to a shallow-angle wedge resonator and preserves both the high-quality cavity edge and the underlying waveguide. The result is a monolithic device with controllable coupling strength, robust alignment and a fabrication route compatible with stable planar photonic circuits.

Figure 1: in-plane and vertical waveguide-resonator coupling geometries, optical micrograph and separation profiles
Article
Phys. Rev. Lett. 110(16), 163901 (2013)
Oscillatory Vertical Coupling between a Whispering-Gallery Resonator and a Bus Waveguide
M. Ghulinyan, F. Ramiro-Manzano, N. Prtljaga, R. Guider, I. Carusotto, A. Pitanti, G. Pucker and L. Pavesi

What the related paper adds

This later paper extends the research direction developed in A fully integrated high-Q Whispering-Gallery Wedge Resonator. This paper reveals that vertical resonator-waveguide coupling is spatially extended and can oscillate as the vertical gap changes. Theory and experiment show repeated passages between under-coupling, critical coupling and over-coupling, replacing the monotonic picture inherited from lateral devices and adding a powerful design degree of freedom.

What this paper adds to the related work

This paper provides an earlier basis for the later development reported in Oscillatory Vertical Coupling between a Whispering-Gallery Resonator and a Bus Waveguide. This paper applies vertical integration to a shallow-angle wedge resonator and preserves both the high-quality cavity edge and the underlying waveguide. The result is a monolithic device with controllable coupling strength, robust alignment and a fabrication route compatible with stable planar photonic circuits.

Proceedings of SPIE journal identification graphic
Proceedings paper
Proc. SPIE 8431, 84311O (2012)
Silicon-based monolithically integrated whispering-gallery mode resonators with buried waveguides
M. Ghulinyan, F. Ramiro-Manzano, R. Guider, N. Prtljaga, G. Pucker and L. Pavesi

What the related paper adds

This paper complements A fully integrated high-Q Whispering-Gallery Wedge Resonator within the same research line. This work demonstrates a silicon-based platform in which a whispering-gallery resonator is fabricated above a buried dielectric waveguide. Separating the two components into different planes enables independent material and thickness choices, stable evanescent access and wafer-scale fabrication of suspended cavities without a fragile tapered-fibre coupler.

What this paper adds to the related work

Alongside Silicon-based monolithically integrated whispering-gallery mode resonators with buried waveguides, this paper develops a complementary part of the problem. This paper applies vertical integration to a shallow-angle wedge resonator and preserves both the high-quality cavity edge and the underlying waveguide. The result is a monolithic device with controllable coupling strength, robust alignment and a fabrication route compatible with stable planar photonic circuits.

Research fields

Top-down

Conventional silicon microfabrication is used to build a silica wedge resonator directly above a buried SiON bus waveguide. Vertical coupling reaches the mode retracted from the wedge edge while preserving a planar, fully integrated chip.

Simulations & fits

Calculated radial-mode profiles guide lateral waveguide placement and explain the different surface overlap of first- and second-order families. Resonance fits separate intrinsic and coupling losses and show where the integrated wedge retains its high quality factor.

Characterization

Optical images, cross-sectional inspection and broadband transmission spectra compare wedge and conventional disk devices. Measured quality factors and mode-family behaviour verify that integration has not simply traded accessible coupling for excessive cavity loss.

RESEARCH TOPICS

CouplingMeasured spectra show integrated access to both radial families without restoring the rough vertical sidewall that the wedge was designed to avoid. The coupling scheme therefore preserves the optical benefit of mode retraction rather than trading it for convenient excitation.MaterialsThe integrated device combines a 400 nm silicon-nitride resonator with a 300 nm silicon-oxynitride strip guide on a silica-based stack, all fabricated with standard lithography, PECVD and etching. Because material thickness, refractive index and process flow are held close between the two, their measured Q difference can be assigned to the boundary geometry and associated scattering rather than to unrelated material changes.ResonatorsThe improvement is therefore not produced by abandoning confinement but by moving the field away from the etched rim and reducing surface-induced loss. The absence or presence of mode doublets provides an additional signature of boundary scattering.
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