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Property institutions for rural land conservation: Towards a post-neoliberal agenda
The delivery of ecosystems services and conservation of biodiversity relies on the control of rural land for the provision of public benefits. Much has been written about the progress of neoliberalisation, typically implying that land management decisions are increasingly being left to market forces. However, less has been made of the areas in which the state has extended its control over land or where freehold rights have been attenuated. At the same time, there are intimations that the neoliberal hegemony may be waning. This paper explores approaches to the governance of rural land beyond the neoliberal agenda, drawing particularly on two cases: the proposals for the privatisation of the Public Forest Estate in England and the subsequent recommendations of an Independent Panel on Forestry, and the emergence of Large Conservation Area initiatives introduced by non-governmental organisations. It is important to recognise that the crafting of institutions determines the mix of private and public values of land and the incentives for management. We focus particularly on three important elements of governance. Institutional blending relates to the ways in which property rights area spread amongst different interested parties. These arrangements identify the residual claimant that bears the risk and final return from land holding. Ultimate oversight of property use requires public trust to be identified. Research is needed on the operation of these institutions in practice. Governments will need to develop approaches to be able to define and promote public values in rural land uses.An initial draft of this paper was written while Ian Hodge held a Cambridge Fellowship at the University of Canterbury. He is grateful for the facilities provided there and particularly to the Erskine Bequest for financial support.This is the accepted of a paper published in the Journal of Rural Studies Volume 36, October 2014, Pages 453–462, doi:10.1016/j.jrurstud.2014.05.00
Effect of polarized optical injection on the wavelength polarization switching and bistability of a 1550nm-VCSEL
We report the first experimental observation of a variety of forms of wavelength polarization switching and bistability with a 1550-nm VCSEL subject to optical injection with different input polarization angles. ©2008 IEEE
New spaces for nature: The re-territorialisation of biodiversity conservation under neoliberalism in the UK
Biodiversity conservation is a fundamentally spatial practice. For more than a century, conservation's leading strategy has been the establishment of protected areas. Governance by the state has been central to conservation's claim to territory. In the UK, the established approach to biodiversity conservation concentrated on spatial strategies of territorialisation to secure particular outcomes in relatively small pieces of land, set aside as protected areas. However, this strategy has begun to change, and conservation's expanding territorial claims have been expressed through new models of large-scale conservation. A series of projects developed by non-governmental conservation organisations seek to extend conservation management over larger areas of land. In this paper we consider these developments as a form of re-territorialisation, a reframing and extension of conservation's spatial claims. We describe how conservation's ambitions have been reformed and extended and discuss evidence on the growth of large-scale biodiversity conservation projects in the UK. We then consider the implications of these changes in the light of the neoliberalisation of conservation.This is the accepted manuscript. The final version is available from Wiley at http://onlinelibrary.wiley.com/doi/10.1111/tran.12050/abstract
Dual-mode lasing in a 1310-nm quantum dot distributed feedback laser induced by single-beam optical injection
Tunable dual-mode lasing is experimentally demonstrated in a 1310-nm quantum dot (QD) distributed-feedback (DFB) laser under single-beam optical injection. The wavelength spacing between the two lasing modes is controlled by injecting the external optical signal into different residual Fabry-Perot modes of the QD DFB laser. The influence of important parameters, i.e., injection strength and bias current, is also analyzed. The simple experimental configuration used to achieve tunable dual-mode lasing and the theoretically superior properties of the QD laser offer exciting prospects for the use of these devices in microwave signal generation and radio-over-fiber applications for future mobile communication networks. © 2013 AIP Publishing LLC
Effects of detuning, gain-guiding, and index antiguiding on the dynamics of two laterally coupled semiconductor lasers
Four examples of laterally coupled semiconductor lasers with different waveguiding structures have been studied using coupled mode theory and allowing for frequency detuning between the lasers. The structures include purely real index guiding, pure gain-guiding, and combinations of index guiding and antiguiding with gain-guiding. The dynamics of these four systems have been explored using AUTO software (standard numerical continuation package), linear stability analysis, and direct integration of the rate equations. Convincing agreement between results obtained by these three methods has been demonstrated, including effects due to variation of laser pumping rate, detuning, and linewidth enhancement factor. A periodicity of behavior with laser separation has been revealed that was previously overlooked. This periodicity has increasing influence on the bifurcations of the system as the structures develop from those with purely real guidance to a combination of index antiguiding and gain-guiding. The laser design and operating parameters used are realistic for a wide range of edge-emitting and surface-emitting lasers of practical importance, so that the dynamics studied here are relevant to real systems of coupled lasers
Mapping bifurcation structure and parameter dependence in quantum dot spin-VCSELs
We consider a modified version of the spin-flip model (SFM) that describes optically pumped quantum dot (QD) spin-polarized vertical-cavity surface-emitting lasers (VCSELs). Maps showing different dynamical regions and those consisting of various key bifurcations are constructed by direct numerical simulations and a numerical path continuation technique, respectively. A comparison between them clarifies the physical mechanism that governs the underlying dynamics as well as routes to chaos in QD spin-VCSELs. Detailed numerical simulations illustrate the role played by the capture rate from wetting layer (WL) to QD ground state, the gain parameter, and the amplitude-phase coupling. By tuning the aforementioned key parameters in turn we show how the dynamical regions evolve as a function of the intensity and polarization of the optical pump, as well as in the plane of the spin relaxation rate and linear birefringence rate, which is of importance in the design of spin lasers promising potential applications. By increasing the capture rate from WL to QD our simulation accurately describes the transition from the QD spin-VCSEL to the quantum well case, in agreement with a previous mathematical derivation, and thus validates the modified SFM equations
Nonlinear dynamics of solitary and optically injected two-element laser arrays with four different waveguide structures: A numerical study
We study the nonlinear dynamics of solitary and optically injected two-element laser arrays with a range of waveguide structures. The analysis is performed with a detailed direct numerical simulation, where high-resolution dynamic maps are generated to identify regions of dynamic instability in the parameter space of interest. Our combined one- and two-parameter bifurcation analysis uncovers globally diverse dynamical regimes (steady-state, oscillation, and chaos) in the solitary laser arrays, which are greatly influenced by static design waveguiding structures, the amplitude-phase coupling factor of the electric field, i.e. the linewidth-enhancement factor, as well as the control parameter, e.g. the pump rate. When external optical injection is introduced to one element of the arrays, we show that the whole system can be either injection-locked simultaneously or display rich, different dynamics outside the locking region. The effect of optical injection is to significantly modify the nature and the regions of nonlinear dynamics from those found in the solitary case. We also show similarities and differences (asymmetry) between the oscillation amplitude of the two elements of the array in specific well-defined regions, which hold for all the waveguiding structures considered. Our findings pave the way to a better understanding of dynamic instability in large arrays of lasers
Stability and bifurcation analysis of spin-polarized vertical-cavity surface-emitting lasers
A detailed stability and bifurcation analysis of spin-polarized vertical-cavity surface-emitting lasers (VCSELs) is presented. We consider both steady-state and dynamical regimes. In the case of steady-state operation, we carry out a small-signal (asymptotic) stability analysis of the steady-state solutions for a representative set of spin-VCSEL parameters. Compared with full numerical simulation, we show this produces surprisingly accurate results over the whole range of pump ellipticity, and spin-VCSEL bias up to 1.5 times the threshold. We then combine direct numerical integration of the extended spin-flip model and standard continuation technique to examine the underlying dynamics. We find that the spin VCSEL undergoes a period-doubling or quasiperiodic route to chaos as either the pump magnitude or polarization ellipticity is varied. Moreover, we find that different dynamical states can coexist in a finite interval of pump intensity, and observe a hysteresis loop whose width is tunable via the pump polarization. Finally we report a comparison of stability maps in the plane of the pump polarization against pump magnitude produced by categorizing the dynamic output of a spin VCSEL from time-domain simulations, against supercritical bifurcation curves obtained by the standard continuation package auto. This helps us better understand the underlying dynamics of the spin VCSELs
Nonlinear dynamics of Long-Wavelength VCSELs subject to polarised optical injection
We present our work analysing the effects of polarised optical injection in Long-Wavelength Vertical-Cavity Surface Emitting Lasers (LW-VCSELs). We review the properties of different phenomena such as polarisation switching (PS) and bistability (PB) as well as on the different nonlinear dynamics (periodic and chaotic) arising in these devices under different cases of polarised optical injection. © 2011 IEEE
All-optical inverter based on polarization switching in long-wavelength VCSELs
All-optical processing of high-speed signals is expected to be a key technology in future photonic networks. VCSELs are very promising devices for these applications due to their inherent advantages. Nonlinear transfer functions can be obtained by using optical injection because it strongly affects the transverse mode and polarization characteristics of VCSELs [1]. Optical injection can be used to obtain polarization switching (PS) of single transverse mode VCSELs. When the polarization of an injected optical field is orthogonal to that of the solitary VCSEL (orthogonal optical injection), PS and bistability are observed [2]. PS by optical injection is expected to be fast and thus suitable for application in all-optical signal-processing systems. In this work we report, for the first time to our knowledge, all-optical inversion operation using PS in a 1550nm single-mode VCSEL induced by orthogonal optical injection. We demonstrate all-optical inversion for NRZ signals at a bit rate of 2.5 Gb/s. An all-fiber system has been developed in order to inject the light from a tunable laser into a commercial 1550nm-VCSEL (RayCan, Co.). The free-running VCSEL emits in the fundamental transverse mode with a linear polarization (parallel polarization) over the whole current range. The subsidiary orthogonal polarization is shifted 0.48 nm to the long wavelength side with respect to the dominant one. Pulsed optical injection was obtained by using a pulse pattern generator and a Mach-Zhender intensity modulator. © 2011 IEEE
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