JEOS:RP - Journal of the European Optical Society Rapid publications
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A method to remotely measure temperature change in a lithium niobate crystal using birefringence
Get PDFWe present a non-contact method of determining temperature change in a lithium niobate crystal. The technique has the advantage of being simple to implement and offers a precision at least as good as conventional temperature measurement methods over large ranges (~200K). A novel application of this technique involves measuring temperature in different regions of the crystal simultaneously, which could be useful for determining stresses and heat diffusion parameters. The technique could be successfully applied to monitor crystal temperature for thermal fixing of holograms or related applications
Optical bonding with fast sol-gel
Get PDFWe investigate here the properties of fast sol-gel for optical bonding. The precursors of the fast sol-gel material are organically modified alkoxides generating a transparent hybrid (organic-inorganic) substance with silica glass-like properties whose index of refraction can be modified by the addition of various metal-oxides. The fast sol-gel method consists of rapid fabrication of a viscous resin and its subsequent dilution for long shelf life use. This material, when used as an adhesive offers the option of either a thermal or UV curing procedure. We demonstrate a bonding strength of ~ 10 MPa when a 15 µm layer is applied between two glass elements. The bonding remained stable after an extensive -40ºC – 120ºC temperature cycling with minimal residual solvent evaporation at 150ºC. The fast sol-gel material was tested for optical bonding between silica bulks, between silica bulk and silicon wafers and as an adhesive in silica fibre couplers
Quality factor and finesse optimization in buried InGaAsP/InP ring resonators
Get PDFQuality factor and finesse of buried In1-xGaxAsyP1-y / InP ring resonators have been optimized in this paper by a very general modelling technique. Limiting effect of propagation loss within the ring has been investigated using a three-dimensional (3D) highly accurate complex mode solver based on mode matching method to analyze bending loss dependence on ring radius and wavelength. Coupling between straight input/output (I/O) bus waveguides and ring resonator has been studied by 3D Beam Propagation Method (BPM), deriving coupling loss and coupling coefficient for a large range of ring radius and bus waveguides-ring distance values (for both polarizations). Ring resonator has been modelled by the transfer-matrix approach, while finesse and quality factor dependence on radius has been estimated for two resonator architectures (including one or two I/O bus waveguides) and for quasi-TE and quasi-TM modes. Guiding structure has been optimized to enhance resonator performance. The modelling approach has been validated by comparing results obtained by our algorithm with experimental data reported in literature. Influence of rejection (at resonance wavelength) at through port on quality factor and finesse has been widely discussed. A quality factor larger than 8 x 105 has been predicted for the ring resonator employing only one I/O bus waveguide and having a radius of 400 μm. This resonator exhibits a rejection of -8 dB at through port
Refractive index tip sensor based on Fabry-Perot cavities formed by a suspended core fibre
Get PDFA Fabry-Perot refractometer based on suspended core fibre is presented. The Fabry-Perot cavities are formed by a section of suspended core fibre between conventional single-mode fibres. This miniature refractive tip sensor is demonstrated for the measurement of the refractive index change by measuring the fringe visibility and through the analysis of the fast Fourier transform. The two methods are compared. The temperature dependence was also characterized
Self-imaging effect in multimode waveguides with longitudinal periodicity
Get PDFThis paper deals with the self--imaging effect in multimode waveguides. Analogies and differences to the free--space case are shown. The fields in multimode waveguides are studied. Particularly, the behavior of the fields is examined, when aperiodic perturbation is introduced
Three-dimensional modelling of scattering loss in InGaAsP/InP and silica-on-silicon bent waveguides
Get PDFA three-dimensional (3D) method for the estimation of scattering loss due to sidewalls roughness in bent optical waveguides is proposed and validated. The approach, based on Volume Current Method (VCM), has been pointed out to accurately calculate the scattering loss as dependent on curvature radius and wavelength. An exponential model has been employed to analytically describe the sidewalls roughness and a 3D mode solver based on mode-matching method has been used to calculate optical field distribution in the bent waveguide cross-section. Scattering loss suffered by two low index contrast waveguides has been investigated by the developed algorithm. For a buried InGaAsP/InP waveguide and a 6 μm x 6 μm Silica-on-Silicon guiding structure scattering loss dependence on bending radius, wavelength, roughness, correlation length and standard deviation has been investigated and discussed. Because of the different index contrast values, InGaAsP/InP waveguide exhibits a scattering loss which is quite six times larger than in Silica-on-Silicon. For both guiding structures, quasi-TM mode shows a larger scattering loss than quasi-TE one
Performance of a solid-state frequency-shifted feedback laser in optical ranging
Get PDFThe performance of a frequency-shifted feedback laser (FSFL) using a Nd:YVO4 crystal as gain medium was investigated as light source in high accuracy optical ranging based on optical-frequency domain reflectometry (OFDR). The FSFL generates a comb of chirped frequency components over a bandwidth of 45GHz with chirp rates of 3.8×1017Hz/s. In OFDR, distance accuracies better than 25um at a data measurement time of 2ms were demonstrated at a standoff distance of 5m. The results show that the FSFL is a promising light source for high accuracy, high speed 3D measurement applications
The development of a compact free spectral range semiconductor laser biosensor
Get PDFWe present a new evanescent field sensor based on InP/InGaAsP ridge waveguide semiconductor lasers. The laser itself forms an integrated sensing chip containing both a light source and a waveguide. Simple modifications are made to readily available devices, meaning that the chips could form very compact and cost effective sensors
Comparison of photoluminescence properties of semiconductor quantum dots and non-blinking diamond nanoparticles and observation of the diffusion of diamond nanoparticles in cells
Get PDFLong term observations of photoluminescence at the single-molecule level were until recently very difficult, due to the photobleaching of organic fluorophore molecules. Although the inorganic semiconductor nanocrystals can overcome this difficulty showing very low photobleaching yield, they suffer from photoblinking. A new marker has been recently introduced, relying on diamond nanoparticles containing photoluminescent color centers. In this work we compare the photoluminescence of single quantum dots (QDs) to the one of nanodiamonds containing a single-color center. Contrary to other markers, photoluminescent nanodiamonds present a perfect photostability and no photoblinking. At saturation of their excitation, nanodiamonds photoluminescent intensity is only three times smaller that the one of QDs. Moreover, the bright and perfectly stable photoluminescence of nanodiamonds allows wide field observations of single nanoparticles motion. We demonstrate the possibility to follow the trajectory of such single particle in cells in culture and characterize its diffusion
Precision measurements of gravity using cold atom sensors
Get PDFWe present a synthetic view of experiments we are performing using atom interferometry to determine the gravitational constant G and to test the Newtonian gravitational law at micrometric distances. Accurate gravity measurements with atom interferometry also find applications in geophysical studies and in satellite missions for the geoid mapping. Experiments in progress, using ultracold atom devices, for applications in geophyiscal and space monitoring will be also described