Interpreting broad emission-line variations I : Factors influencing the emission-line response

We investigate the sensitivity of the measured broad emission-line responsivity dlog f_line/dlog f_cont to continuum variations in the context of straw-man BLR geometries of varying size with fixed BLR boundaries, and for which the intrinsic emission-line responsivity is known a priori. We find for a generic emission-line that the measured responsivity, delay and maximum of the cross-correlation function are correlated for characteristic continuum variability timescales T_char less than the maximum delay for that line tau_max(line) for a particular choice of BLR geometry and observer orientation. The above correlations are manifestations of geometric dilution arising from reverberation effects within the spatially extended BLR. When present, geometric dilution reduces the measured responsivity, delay and maximum of the cross-correlation function. We also find that the measured responsivity and delay show a strong dependence on light-curve duration, with shorter campaigns resulting in smaller than expected values, and only a weak dependence on sampling rate. The observed strong negative correlation between continuum level and line responsivity found in previous studies cannot be explained by differences in the sampling pattern, light-curve duration or in terms of purely geometrical effects. To explain this and to satisfy the observed positive correlation between continuum luminosity and BLR size in an individual source, the responsivity-weighted radius must increase with increasing continuum luminosity. For a BLR with fixed inner and outer boundaries this requires radial surface emissivity distributions which deviate significantly from a simple power-law, and in such a way that the intrinsic emission-line responsivity increases toward larger BLR radii, in line with photoionisation calculations.Comment: 21 pages, 17 figures, accepted for publication in MNRAS July 201

Upper Bound Imposed upon Responsivity of Optical Modulators

We study theoretically the responsivity of optical modulators. For the case of linear response we find using perturbation theory an upper bound imposed upon the responsivity. For the case of two mode modulator we find a lower bound imposed upon the optical path required for achieving full modulation when the maximum birefringence strength is given

Current responsivity of semiconductor superlattice THz-photon detectors

The current responsivity of a semiconductor superlattice THz-photon detector is calculated using an equivalent circuit model which takes into account the finite matching efficiency between a detector antenna and the superlattice in the presence of parasitic losses. Calculations performed for currently available superlattice diodes show that both the magnitudes and the roll-off frequencies of the responsivity are strongly influenced by an excitation of hybrid plasma-Bloch oscillations which are found to be eigenmodes of the system in the THz- frequency band. The expected room temperature values of the responsivity (2-3 A/W in the 1-3 THz-frequency band) range up to several percents of the quantum efficiency $e/\hbar\omega$ of an ideal superconductor tunnel junction detector. Properly designed semiconductor superlattice detectors may thus demonstrate better room temperature THz-photon responsivity than conventional Schottky junction devices.Comment: Revtex file, uses epsf, 11 pages. 11 eps-figures; EPS-files generated by scanner, original higher resolution line drawings available from [email protected] by regular mail or fa

High-speed GaAlAs/GaAs p-i-n photodiode on a semi-insulating GaAs substrate

A high-speed, high-responsivity GaAlAs/GaAs p-i-n photodiode has been fabricated on a GaAs semi-insulating substrate. The 75-µm-diam photodiode has a 3-dB bandwidth of 2.5 GHz and responsivity of 0.45 A/W at 8400 Å (external quantum efficiency of 65%). The diode is suitable for monolithic integration with other optoelectronic devices

Addressing criminality in childhood: is responsivity the central issue?

The responsivity principle is the third element of the now well-established risk–need–responsivity (RNR) model of offender rehabilitation. Accruing evidence suggests it is often sacrificed in intervention programs. We aim to demonstrate the central importance of this principle when designing offender interventions by describing the results of a successful, highly responsive intervention for very young children (aged 7 upward) who have offended. A small slice of the offending population as a whole, child offenders are nevertheless tomorrow’s serious, violent, and prolific lawbreakers, yet little is understood about what reduces their risk. Recent developments on responsivity are reviewed, before presenting the evaluation indicating significant and sustained drops in risk of recidivism. In-program factors such as the nature and dosage of interventions are examined, alongside outcome data. The article discusses how RNR and other models might apply to this particularly young and underresearched age group. </jats:p