Q factor

About: Q factor is a research topic. Over the lifetime, 8387 publications have been published within this topic receiving 163135 citations. The topic is also known as: Q factor.

Liquid-core optical ring-resonator sensors

Abstract: We have demonstrated a novel sensor architecture based on a liquid-core optical ring-resonator (LCORR) in which a fused silica capillary is utilized to carry the aqueous sample and to act as the ring resonator. The wall thickness of the LCORR is controlled to a few micrometers to expose the whispering gallery mode to the aqueous core. Optical characterization with a water-ethanol mixture shows that the spectral sensitivity of the LCORR sensor is approximately 2.6 nm per refractive index unit. A model based on Mie theory is established to explain the experimental results. The LCORR takes advantage of the high sensitivity, small footprint, and low sample consumption with the ring resonator, as well as the efficient fluidic sample delivery with the capillary, and will open an avenue to future multiplexed sensor array development.

All-optical logic based on silicon micro-ring resonators

Abstract: We demonstrate all-optical logic in a micron-size silicon ring resonator based on the free-carrier dispersion effect in silicon. We show AND and NAND operation at 310 Mbit/s with ∼10-dB extinction ratio. The free-carrier-lifetime-limited bit-rate can be significantly improved by active carrier extraction.

High- Q surface-plasmon-polariton whispering-gallery microcavity

Abstract: Surface plasmon polaritons (SPPs) are electron density waves excited at the interfaces between metals and dielectric materials (1). Owing to their highly localized electromagnetic fields, they may be used for the transport and manipulation of photons on subwavelength scales (2-9). In particular, plasmonic resonant cavities represent an application that could exploit this field compression to create ultrasmall-mode-volume devices. A key figure of merit in this regard is the ratio of cavity quality factor, Q (related to the dissipation rate of photons confined to the cavity), to cavity mode volume, V (refs 10, 11). However, plasmonic cavity Q factors have so far been limited to values less than 100 both for visible and near-infrared wavelengths (12-16). Significantly, such values are far below the theoretically achievable Q factors for plasmonic resonant structures. Here we demonstrate a high-Q SPP whispering-gallery microcavity that is made by coating the surface of a high-Q silica microresonator with a thin layer of a noble metal. Using this structure, Q factors of 1,376 ± 65 can be achieved in the near infrared for surface-plasmonic whispering-gallery modes at room temperature. This nearly ideal value, which is close to the theoretical metal-loss-limited Q factor, is attributed to the suppression and minimization of radiation and scattering losses that are made possible by the geometrical structure and the fabrication method. The SPP eigenmodes, as well as the dielectric eigenmodes, are confined within the whispering-gallery microcavity and accessed evanescently using a single strand of low-loss, tapered optical waveguide (17, 18). This coupling scheme provides a convenient way of selectively exciting and probing confined SPP eigenmodes. Up to 49.7 per cent of input power is coupled by phase-matching control between the microcavity SPP and the tapered fibre eigenmodes.

Octave-spanning frequency comb generation in a silicon nitride chip.

Abstract: We demonstrate a frequency comb spanning an octave via the parametric process of cascaded four-wave mixing in a monolithic, high-Q silicon nitride microring resonator. The comb is generated from a single-frequency pump laser at 1562 nm and spans 128 THz with a spacing of 226 GHz, which can be tuned slightly with the pump power. In addition, we investigate the RF amplitude noise characteristics of the parametric comb and find that the comb can operate in a low-noise state with a 30 dB reduction in noise as the pump frequency is tuned into the cavity resonance.

Modified Butterworth-Van Dyke circuit for FBAR resonators and automated measurement system

Abstract: Microwave Film Bulk Acoustic Resonators (FBARs) may be characterized by means of the Mason transmission line model, but for parameter extraction and design studies, the lumped Butterworth-Van Dyke (BVD) model is more useful. We propose a modification to the standard five element BVD model, in which a second resistor is added in series with the plate capacitance C/sub 0/. This improves the model predictions as compared to the data obtained from a network analyzer (NWA). Here, the modified model will be developed in terms of the resonant frequencies, effective coupling constant k/sub t//sup 2/, and the quality factor Q, as determined from the S parameters of an FBAR measured by the NWA. To evaluate the FBAR resonators on a routine basis, an automated data acquisition and parameter extraction method based on the Modified Butterworth-Van Dyke model (MBVD) is described. An Agilent Technologies 8753ES NWA operating under Personal Computer control is used to acquire and process FBAR data by means of a custom HPVEE/sup TM/ program, which transfers data from the NWA, and extracts the six MBVD circuit parameters. Excellent agreement is obtained between the measured data for a typical FBAR resonator and calculated "postdictions" obtained from the MBVD circuit. Coupled with the automated method, which takes about 10 seconds per resonator to perform a complete extraction cycle, a computer controlled probing station is used to acquire data from several hundred resonators on the wafer upon which the FBARS were fabricated. With this speed and probing capability, it is feasible to wafer map the FBARs for uniformity. Contour plots of the measured resonant frequency and coupling constant k/sub t//sup 2/ will be presented to illustrate the capability.