Showing papers by "Martin Kristensen published in 2000"
TL;DR: In this paper, a continuous temperature ramp method was used to determine the long-term stability of UV-induced fiber Bragg gratings using a continuous isochronal anneal method.
Abstract: We present a new method for determining the long-term stability of UV-induced fiber Bragg gratings. We use a continuous temperature ramp method in which systematic variation of the ramp speed probes both the short- and long-term stability. Results are obtained both for gratings written in D2 loaded and nonloaded fibers. The results for the nonloaded fibers are in good agreement with those previously obtained. Precise predictions of the grating decay were made. We find good agreement with a broad trap energy distribution where the defects with the lowest energy decay first. For the D2 loaded fiber grating we resolve two separate energy distributions, suggesting that two different defects are involved. The experiments show that complicated decays originating from various energy distributions can be analyzed with this continuous isochronal anneal method. The results have both practical applications in determining the long-term stability of fiber gratings and fundamental importance since they can be used to d...
58 citations
TL;DR: In this article, the guidelines for designing planar waveguides based on introducing line-defects in two-dimensional photonic-crystal slabs are obtained by comparing calculations on 2D structures with dispersion relations for the media above and below the slab.
Abstract: Guidelines for designing planar waveguides based on introducing line-defects in two-dimensional photonic-crystal slabs are obtained by comparing calculations on two-dimensional structures with dispersion relations for the media above and below the slab.
30 citations
TL;DR: In this paper, the second-order optical nonlinearity is located near the interface between differently doped glass layers and the ratio between the main elements of the secondorder nonlinear optical susceptibility tensor, χ33(2) and χ31(2), is significantly smaller than three.
Abstract: Electric-field poled silica-based waveguides are characterized by measurements of second-harmonic generation (SHG) and of the linear electro-optic effect (LEO). A SHG scanning technique allowing for high-resolution imaging of poled devices is demonstrated. Scans along the direction of the poling field show that the second-order optical nonlinearity is located near the interface between differently doped glass layers. Both SHG and LEO measurements indicate that the ratio between the main elements of the second-order nonlinear optical susceptibility tensor, χ33(2) and χ31(2), is significantly smaller than three.
30 citations
TL;DR: In this article, the authors reported very large second-harmonic signals were observed from thermally poled silica waveguide samples, while only small linear electro-optic effects were detected.
Abstract: The authors report very large second-harmonic signals were observed from thermally poled silica waveguide samples. In contrast, only small linear electro-optic effects were detected. Secondary ion mass spectrometry measurements show that large amounts of positive ions, in particular silver ions, are injected during poling. The ions originate from the painted-on top poling electrode.
29 citations
TL;DR: In this paper, a novel twin-core coupling at shorter wavelengths but not at longer wavelengths (∼15 μm) was achieved within an air-silica structured optical fiber.
17 citations
TL;DR: In this article, the spatial resolution in normal reflection mode can be better than 1 μm for second-harmonic images and a simple qualitative description of this operation mode is suggested and found to be in good agreement with the results obtained.
Abstract: Second-harmonic scanning optical microscopy (SHSOM) is performed on electric-field poled silica-based waveguides. Two operation modes of SHSOM are considered. Oblique transmission reflection and normal reflection modes are used to image the spatial distribution of nonlinear susceptibilities in the sample surface plane and in depth. It is shown that the spatial resolution in normal reflection mode can be better than 1 μm for second-harmonic images. A simple qualitative description of this operation mode is suggested and found to be in good agreement with the results obtained. Advantages and limitations of the two operation modes when used for SHSOM studies of poled silica-based waveguides are discussed. The influence of surface defects on the resulting second-harmonic images is also considered.
14 citations
07 Mar 2000
TL;DR: In this article, a distributed feedback fiber laser operating at wavelengths above the L-band was presented for the first time and a numerical analysis that predicts the optimum design of these lasers has been developed.
Abstract: Distributed feedback fiber lasers operating at wavelengths above the L-band an presented for the first time. Furthermore, a numerical analysis that predicts the optimum design of these lasers has been developed.
5 citations
01 Jan 2000
3 citations
10 Sep 2000
TL;DR: In this article, a photonic crystal fiber (PCF) with multiple cores was fabricated by drawing a fiber preform from stacked glass tubes, and transmission is high through each core despite many unintentional defects in the cladding.
Abstract: Summary form only given We have fabricated a photonic crystal fiber (PCF) with multiple cores by drawing a fiber preform from stacked glass tubes Transmission is high through each core despite many unintentional defects in the cladding indicating that the guidance is determined by the holes near to the core
3 citations
Patent•
12 May 2000
TL;DR: In this paper, a bending sensor using long-period fiber gratings (LPG) was proposed to determine the bending amplitude and direction, where the intrinsic properties of the fiber and the bend sensitivity of LPG were utilized.
Abstract: The present invention relates to an optical based bending sensor. In particular, the present invention relates to a fibre-based bending sensor for the determination of the direction and the amplitude of a bend. The present invention further relates to fibre-based bending sensors using long-period fibre gratings (LPG), in which the intrinsic properties of the fibre and the bend sensitivity of LPG is utilised. In a preferred embodiment, the connection between the Core Concentricity Error (CCE) of the fibre and the LPG in the asymmetric bend behaviour results in coupling resonance between the core and the cladding modes. Thereby a relative splitting of transmission peaks in the spectrum of the LPG is induced, which is used to determine the bending amplitude and direction.