Terms Of Birefringence Research Articles

Enhancing polarization maintenance and spectral filtering in negative curvature hollow-core fibers

A new design of polarization-maintaining and spectral filtering negative curvature hollow-core fiber tailored for the telecommunication bands in the near-infrared region is presented. The optical fiber, consisting of a six-tube silica structure, incorporates vertically nested tubes anchored radially by a pole structure. By contrast, standard nested tubes in the horizontal direction form the asymmetric fiber structure, which encounters birefringence. This unique fiber design not only preserves the polarization states of light but also exhibits frequency selective transmission exclusively in the vertical direction due to the pole structure. Through fiber design optimization, a transmission loss below 0.1 dB/km for spectrally filtered wavelengths is achieved, with birefringence on the order of 10−5 within the wavelength range of 1.45 µm to 1.60 µm. These results demonstrate significant improvements in terms of birefringence, distinct loss separation between horizontally and vertically polarized states, and a reduced number of spectrally filtered wavelengths compared to previously reported findings. The proposed fiber design holds untapped potential for applications requiring selective transmissions with specific polarization.

Investigating the cross core octagonal photonic crystal fiber with high birefringence: A design and analysis study

In optical communication systems, the quality of transmitted signals can be compromised by random birefringence, which is caused by irregularities in the core-cladding boundaries. To eliminate this problem, high birefringence can be introduced through an asymmetrical fiber structure. Photonic crystal fibers (PCFs) are an ideal solution due to their high intrinsic index contrast and design flexibility, which allows for high birefringence to be achieved. This paper introduces a new PCF design that takes advantage of these features to provide a higher modal birefringence compared to conventional fibers. The design is a cross-core octagonal-shaped fiber, and its performance is evaluated in terms of birefringence and beat length. The results indicate that the proposed fiber provides a birefringence range of 1.3E-3 to 1.6E-3 for a transmission wavelength range of 1.4 μm to 1.8 μm (S, C, and L Bands) and a minimum beat length range of 1.02 mm to 1.12 mm. This fiber design enables long-haul fiber communication without polarization mode dispersion, even under conditions of external perturbation.

Manufacturing Signatures of Injection Molding and Injection Compression Molding for Micro-Structured Polymer Fresnel Lens Production.

Injection compression molding (ICM) provides enhanced optical performances of molded polymer optics in terms of birefringence and transmission of light compared to Injection molding (IM). Nevertheless, ICM requires case-dedicated process optimization to ensure that the required high accuracy geometrical replication is achieved, particularly especially in the case of surface micro-features. In this study, two factorial designs of experiments (DOE) were carried out to investigate the replication capability of IM and ICM on a micro structured Fresnel lens. A laser scanning confocal microscope was employed for the quality control of the optical components. Thus, a detailed uncertainty budget was established for the dimensional measurements of the replicated Fresnel lenses, considering specifically peak-to-valley (PV) step height and the pitch of the grooves. Additional monitoring of injection pressure allowed for the definition of a manufacturing signature, namely, the process fingerprint for the evaluation of the replication fidelity under different process conditions. Moreover, considerations on the warpage of parts were related to a manufacturing signature of the molding processes. At last, the global part mass average and standard deviation were measured to correlate local geometrical replication performances with global part quality trends.

Liquid crystal photonic crystal fibre with high non‐linearity and birefringence

A novel design of highly birefringent tellurite liquid crystal photonic crystal fibres (PCFs) with low confinement loss and high non-linearity is introduced. The simulation results are obtained by using full-vectorial finite-difference method. The analysed parameters are birefringence, hybridness, effective mode area and non-linearity for the two fundamental polarised modes. Significant improvements of PCFs in terms of birefringence, confinement losses and non-linearity are demonstrated by careful investigation of the structure geometrical parameters and temperature. The reported design has high birefringence of 0.09094 and high non-linearity γ of 2502 and 1900 W−1 km−1 for the quasi-transverse electric and quasi-transverse magnetic modes, respectively, at the operating wavelength of 1.55 µm with low losses for the two fundamental polarised modes.

Directed Organization of DNA Filaments in a Soft Matter Template

We have developed a noninvasive, all-optical, holographic technique for permanently aligning liquid crystalline DNA filaments in a microperiodic template realized in soft-composite (polymeric) materials. By combining optical intensity holography with a selective microfluidic etching process, a channelled microstructure has been realized which enables self-assembly of DNA. The striking chemicophysical properties of the structure immobilize the DNA filaments within the microchannels without the need of any kind of surface chemistry or functionalization. Polarized optical, confocal, and electronic microscopies have been used for characterizing the DNA geometry inside the microchannels in terms of birefringence, fluorescence, and nanoscale organization properties. In particular, observation of a far-field diffraction pattern confirms a periodic organization of the DNA filaments inside the polymeric template.

Blends of an azomethacrylic block copolymer for volume holographic storage using low energy 10 ms light pulses

Polymer blends of a poly (methylmethacrylate) (PMMA) homopolymer and an azomethacrylic diblock copolymer (BC) are investigated for the recording of holographic polarization gratings. Blends with an azobenzene content down to 2, 1 and 0.5wt.%, and good optical quality have been prepared. Their morphology associated with microphase separation as well as the achieved photo-induced anisotropy in terms of birefringence and dichroism are similar to those obtained for the original BC. Volume holographic polarization gratings have been stored in thick films (up to 500μm) of these blends using two oppositely circularly polarized 488nm light pulses of 100ms and 10ms with a constant value of the energy density of 50mJ/cm2 (each beam). Although the efficiency of the gratings decays with time, a final equilibrium efficiency, in the range of 10−4, remains in both cases. Up to 20 polarization gratings, with efficiencies higher than 3.5×10−5, have been successfully multiplexed using light pulses as short as 10ms, which is an order of magnitude shorter than that reported in previous investigations.

Prediction of birefringence distribution for optical glass lens

Abstract Based on the viscoelastic theory, simulations were carried out on glass-lens forming processes. In addition, the birefringence distribution was calculated by stress-optic relation. First, to verify this viscoelastic simulation, FEM analysis was performed with the same material properties and process conditions used in the Bruckner's experiment. The result of the analysis was compared with Nadai's and Bruckner's results. The simulation results were in good agreement with the deformation and birefringence distribution in the experimental results. Finally, the FEM simulation technique was applied to actual LD-lens. The simulation was performed for each different cooling rate and the results were compared to each other in terms of birefringence. To investigate the effect of initial preform shape to optical property, a simulation was performed by using the new-proposed-shape-preform and the results were compared to the present shape in terms of birefringence.

Optical activity of a single MnAs cluster: Birefringence or Kerr effect

We have grown In 0.54Ga 0.46As:Mn/MnAs granular paramagnetic–ferromagnetic hybrid structures by metal–organic vapor-phase epitaxy. The MnAs clusters have a Curie temperature of about 320 K. We have studied the optical activity of individual ferromagnetic MnAs clusters embedded in the paramagnetic In 0.54Ga 0.46As:Mn matrix at room temperature by far-field depolarization measurements. A scanning near-field optical microscopy set-up in constant height mode ( ≈ 100 nm above the sample surface) was used to achieve a high spatial resolution. Individual MnAs clusters rotate the linear polarization of the incoming light by almost 2 ∘ in this reflection geometry. This optical activity was analyzed in terms of birefringence and polar Kerr effect and correlated with the structural and magnetic properties of the MnAs clusters as determined by ferromagnetic resonance measurements. The optical activity of the MnAs clusters turns out to be dominated by linear birefringence caused by the uniaxial symmetry of the hexagonal crystal structure of MnAs. The polar Kerr effect plays a minor role in this experiment.

Coherent moire technique for obtaining slope and curvature of stress patterns

A method for studying the stress-induced birefringence over the area of a sample by simultaneous application of shearing interferometry and moiré techniques is dealt with. This is a method by which one can have the fringe pattern for the first and second derivative of the birefringence distribution in the form of the slope and curvature of the test wavefront. There is, however, a method of obtaining the second derivative fringe system by using a four-exposure holographic technique in which the pattern is generated by shearing of two holograms of deformed surface. This is related to stress distribution in the structure under test. In the presented method, on the other hand, the test wavefront carries the information of stress distribution in terms of birefringence. The suggested experimental setup can provide the slope and curvature of the test wavefront in a single exposure.

Forward scattering (polarisation spectroscopy) of resonance radiation in partially coherent fields

Previous theoretical treatments of polarisation spectroscopy (forward scattering) are generalised so as to include laser temporal coherence effects. It is shown that for the general case it is impossible to describe the signal obtained in terms of birefringence and dichroism. The generalisation of the concept of the polarisability tensor is given together with the approximate expression for the signal in terms of it. The simple example of the Jg=0 to Je=1 transition in the forward scattering experiment is discussed in detail. Comparison is made between the signal lineshapes obtained for the phase diffusion model and the chaotic field model. The necessity of taking into account the statistical properties of the laser light in the forward scattering (polarisation spectroscopy) experiment is pointed out.