Microlens Formation Research Articles

Detection of optical non-linearities in amorphous semiconductors by caustic crossing in an intensity-modulated laser beam

Optical non-linearities (ONL) have been studied in a-Si:H and a-Se thin films by putting the films in or near the caustic of highly-focused laser beams at sub-band gap energies, while the beam intensity is periodically altered by an electro-optic modulator. In a-Si:H non-linear absorption is seen, together with non-linear refraction of the laser beam at the highest intensities. In the a-Se samples additional, persistent ONL due to structural modifications of the films are observed. They include the appearance of interference fringes and modulation of the reflectance due to the formation of microlenses.

Single-step laser fabrication of refractive microlenses in semiconductor-doped glasses

Exposure of semiconductor-doped glasses to above-band-gap focused cw laser radiation results in the controllable formation of microlenses. A laser-driven thermal runaway is proposed to explain the low powers required for the process. A linear array of eight identically prepared microlenses is characterized and shown to exhibit diffraction-limited performance.

Fabrication of bifocal microlenses on InP and Si by Ar ion beam etching

The fabrication process for the formation of bifocal microlenses on InP and Si substrates by Ar ion beam etching is described. Calculation and experimental results demonstrate that when InP and Si substrates coated with spherical photoresist mask are etched by Ar ion beams with reasonable etching parameters, the shape of the etched lenses will still be spherical and the curvature radius of the etched lens R = R r k (where R r is the radius of the spherical photoresist mask, k is the etch ratio of the substrate to mask). Therefore during the etching process when the etching parameters such as ion beam energy or ion incident angle are suitably changed, a bifocal microlens will be realized.

Simulation of coupling efficiency between a laser diode and a single‐mode fiber with microlens end

AbstractA microlens fabricated on the end of a single‐mode fiber (SMF) can increase the coupling efficiency to laser diodes (LDs). A simulation of microlens formation and an analysis of the resulting coupling efficiency have been performed. The results are in good agreement with data obtained experimentally.

Distributed index formation of planar microlens

AbstractFinding the distributed index formation in the fabrication of planar microlens is important in realizing the optimization of the conditions controlling the distribution as it determines the optical properties. The system is modeled under the assumption that the penetration of the metal dopant ions follows the drift‐diffusion equation. Before this equation is solved, the diffusion constant and the mobility of metal ions in a glass substrate are measured. It is found that the diffusion constant is strongly dependent on the ion concentration. Based on these findings, the drift‐diffusion equation is analyzed numerically to find the concentration distribution in the planar microlens. It is found that the thermal diffusion with a strong concentration dependence contributes significantly to the formation of concentration profile without a tail.

Microlens formation on VAD single-mode fibre ends

The letter describes microlens formation process on VAD single-mode fibre ends by a chemical-etching/fire-polishing technique. No central dip in the VAD fibres leads to high-quality lens formation.

Structural changes in bilayer membranes by multivalent ions

Formation of microlenses, a reduction in thickness, and a change in mechanical properties have been observed when Ca 2+ or other multivalent ions are added to bathing solutions of Mueller-Rudin membranes of acidic phospholipids. The observations are interpreted as an extrusion of residual solvent from the hydrocarbon core of the bilayer due to changes in packing imposed by the reduction of electrostatic repulsion of the head groups.