Linear polarization Yb³⁺-doped fiber laser with novel innerclad structures

Results on high radiance Yb3+-doped fiber lasers with novel double innerclad structures (double-D clad and four hole) and polarized output at ≈1090 nm are presented. We have demonstrated >40% of the total output power being polarized, making the fiber laser suitable for LIDAR and second-harmonic generation (SHG) applications. It also showed a 10-nm tuning range with low (less than 10 mW) average power variations. The narrow linewidth source was pumped with a low cost, low brightness laser diode, and exhibited a relatively low slope efficiency, which gives room for improvement by using a 976-nm pump source where Yb3+ has a narrower linewidth and at least five times higher absorption

High proportion of cactus species threatened with extinction

This is the author accepted manuscript. The final version is available from Nature Publishing Group via the DOI in this record.Consejo Nacional de Ciencia y Tecnologí

Characterizing single-mode fibres and single-mode fibre lenses

SIGLEAvailable from British Library Document Supply Centre- DSC:DX84442 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Weak Guidance, Multi-index and Exact Mode Eigenvalue Calculation for Mode Intensity Profiles in Tapers

The fundamental mode intensity profile is calculated for different points along the transition of an optical fibre taper from standard size (125 μm external cladding diameter and 8 μm core diameter) down to micro (1 μm external fibre diameter) and submicro size (down to 440 nm fibre diameter) at 1550 nm operational wavelength. The first section of the taper was evaluated using weak guidance approximation, the second section was treated as a three-index layer structure (double-clad) and evaluated with eigenvalue equations for three refractive indices. An external medium being a liquid with a refractive index close to silica is being considered. The third and thinnest section of the taper was evaluated with the exact mode eigenvalue equation. The results show that the fundamental mode intensity for the third section show a discontinuity just at the fibre edge with a peak amplitude larger than the optical field at the centre of the fibre. The taper shape that complies with the adiabaticity criterion and how the mode intensity profile and the spot size (Petermann 1 definition) of the fundamental mode change along their position on the taper were determined

Dual tapered optical fiber for simultaneous detection of curvature and strain

We present a study of simultaneous detection of curvature and strain in optical fiber. This contains a micro tapered section and a nano tapered section. The transmission spectrum shows interference of multiple modes, and the frequency of the modulation can be used to distinguish and monitor specific physical parts of the fiber structure. The curvature detection is achieved using one specific modulation frequency component; this component shows an intensity modulation with a sensitivity of 0.26 dB/m−1. The strain information is extracted by applying a phase analysis over a second spatial frequency component; this analysis shows a sensitivity close to 8 mrad/με. The strain phase analysis exhibits a linear response, and the intensity curvature data indicates an exponential model. The proposed signal analysis can be employed for simultaneous detection in optical fiber interferometric sensors