Photonic clocks, Raman lasers, and Biosensors on Silicon

Micro-resonators on silicon having Q factors as high as 500 million are described, and used to demonstrate radio-frequency mechanical oscillators, micro-Raman and parametric sources with sub-100 microwatt thresholds, visible sources, as well as high-sensitivity, biological detectors

Ultra-high-Q microcavity operation in H2O and D2O

Optical microcavities provide a possible method for boosting the detection sensitivity of biomolecules. Silica-based microcavities are important because they are readily functionalized, which enables unlabeled detection. While silica resonators have been characterized in air, nearly all molecular detections are performed in solution. Therefore, it is important to determine their performance limits in an aqueous environment. In this letter, planar microtoroid resonators are used to measure the relationship between quality factor and toroid diameter at wavelengths ranging from visible to near-IR in both H2O and D2O, and results are then compared to predictions of a numerical model. Quality factors (Q) in excess of 10^8, a factor of 100 higher than previous measurements in an aqueous environment, are observed in both H2O and D2O

Fiber-coupled erbium microlasers on a chip

An erbium-doped, toroid-shaped microlaser fabricated on a silicon chip is described and characterized. Erbium-doped sol-gel films are applied to the surface of a silica toroidal microresonator to create the microcavity lasers. Highly confined whispering gallery modes make possible single-mode and ultralow threshold microlasers

Ultra-high-Q toroid microcavities on a chip

We demonstrate microfabrication of ultra-high-Q microcavities on a chip, exhibiting a novel toroid-shaped geometry. The cavities possess Q-factors in excess of 100 million which constitutes an improvement close to 4 orders-of-magnitude in Q compared to previous work [B. Gayral, et al., 1999]

Fabrication and coupling to planar high-Q silica disk microcavities

Using standard lithographic techniques, we demonstrate fabrication of silica disk microcavities, which exhibit whispering-gallery-type modes having quality factors (Q) in excess of 1 million. Efficient coupling (high extinction at critical coupling and low, nonresonant insertion loss) to and from the disk structure is achieved by the use of tapered optical fibers. The observed high Q is attributed to the wedged-shaped edge of the disk microcavity, which is believed to isolate modes from the disk perimeter and thereby reduce scattering loss. The mode spectrum is measured and the influence of planar confinement on the mode structure is investigated. We analyze the use of these resonators for very low loss devices, such as add/drop filters

Ultralow-threshold microcavity Raman laser on a microelectronic chip

Using ultrahigh-Q toroid microcavities on a chip, we demonstrate a monolithic microcavity Raman laser. Cavity photon lifetimes in excess of 100 ns combined with mode volumes typically of less than 1000 µm^3 significantly reduce the threshold for stimulated Raman scattering. In conjunction with the high ideality of a tapered optical fiber coupling junction, stimulated Raman lasing is observed at an ultralow threshold (as low as 74 µW of fiber-launched power at 1550 nm) with high efficiency (up to 45% at the critical coupling point) in good agreement with theoretical modeling. Equally important, the wafer-scale nature of these devices should permit integration with other photonic, mechanical, or electrical functionality on a chip

Thermo-optic locking of a semiconductor laser to a microcavity resonance

We experimentally demonstrate thermo-optic locking of a semiconductor laser to an integrated toroidal optical microresonator. The lock is maintained for time periods exceeding twelve hours, without requiring any electronic control systems. Fast control is achieved by optical feedback induced by scattering centers within the microresonator, with thermal locking due to optical heating maintaining constructive interference between the cavity and the laser. Furthermore, the optical feedback acts to narrow the laser linewidth, with ultra high quality microtoroid resonances offering the potential for ultralow linewidth on-chip lasers.Comment: 6 pages, 6 figure

An Experimental Platform for the Analysis of Polydisperse Systems Based on Light Scattering and Image Processing

In this work an experimental platform for light scattering analysis has been developed using image sensors, as CCD or CMOS. The main aim of this activity is the investigation of the feasibility of using these types of sensors for polydisperse systems analysis. The second purpose is the implementation of an experimental platform which is enough versatile to permit the observation of different phenomena in order to develop novel sensors/approach using data fusion

Detailed design of a lattice composite fuselage structure by a mixed optimization method

In this paper, a procedure for designing a lattice fuselage barrel has been developed and it comprises three stages: first, topology optimization of an aircraft fuselage barrel has been performed with respect to weight and structural performance to obtain the conceptual design. The interpretation of the optimal result is given to demonstrate the development of this new lattice airframe concept for the fuselage barrel. Subsequently, parametric optimization of the lattice aircraft fuselage barrel has been carried out using Genetic Algorithms on metamodels generated with Genetic Programming from a 101-point optimal Latin hypercube design of experiments. The optimal design has been achieved in terms of weight savings subject to stability, global stiffness and strain requirements and then was verified by the fine mesh finite element simulation of the lattice fuselage barrel. Finally, a practical design of the composite skin complying with the aircraft industry lay-up rules has been presented. It is concluded that the mixed optimization method, combining topology optimization with the global metamodel-based approach, has allowed to solve the problem with sufficient accuracy as well as provided the designers with a wealth of information on the structural behaviour of the novel anisogrid composite fuselage design