CERTAIN ENVIRONMENT, ECONOMIC AND SOCIAL ASPECTS OF THE HIGH NATURAL VALUE (HNV) FARMING: ROMANIAN’S STATE OF THE ART

HNV farming is a new concept that describes those farming systems in Europe that have the widest biodiversity. It brings an alternative and complementary approach to the typology that has become conventional by nature conservation. The paper presents the role of the HNV farming system for the conservation of rare and threatened species and habitats in protected areas as well as preservation of biodiversity inEurope, which largely depends on the continuation of traditional agricultural practices in much wider areas of European rural space. Thus, one of the major problems in the implementation of agricultural policies in many European countries has been made aware: support for ,,nature” focuses on ,,designated areas” while support for ,,agriculture” flows abundantly towards large, intensive producers. This situation needs to be reconsidered because in the distribution of European funds there has been a recommendation on the major change towards environmentally beneficial land use

InAsP/InGaAsP Periodic Gain Structure for 1.5µm Vertical Cavity Surface Emitting Laser Applications

We have studied the capabilities of chemical beam epitaxy (CBE) to produce high-gain media for long-wavelength (1.5 mu m) vertical cavity surface emitting lasers (VCSELs). Using a parameter pair of low growth temperature and small V/III ratio the integration of up to 15 highly strained (1.78%) InAsP quantum wells (QWs) into a periodic gain structure (PGS) is successfully demonstrated. In this work we present data of atomic force microscopy (AFM), X-ray diffraction, reflectivity and electro-luminescence measurements that prove the very good structural and optical quality of this CBE grown PGS. As an alternative to conventional multi quantum well(MQW) systems as active layers, a high-performance PGS may be used in a VCSEL structure to reduce the very strict requirements on the InP-based distributed Bragg reflectors (DBRs) or to increase the achievable output power. Due to the use of thickness-reduced InP-based DBRs in conjunction with a PGS as the active region the fabrication of fully epitaxial grown long-wavelength VCSELs might also be possible with CBE. (C) 1998 Elsevier Science B.V. All rights reserved