The recent developments in optics and photonics require novel, simple and fast methods of fabrication of miniaturized
integrated devices with well controlled optical functions. Among other optical elements, microlenses or microcavities
integrated on optical fibers, waveguides of miniaturized laser sources revealed of great interest due to their applications
for coupling, focusing of collimating light. A simple and low cost technique to implement a polymer micro-component at
the extremity of optical fiber was proposed. The process is based on a spatially controlled photopolymerization that is
induced by a laser beam emerged from the optical fiber. Thus, the microlens is directly aligned with the fiber core. The
polymer tips have shown to exhibit various shapes as a function of the photonic parameters and the chemical
composition of formulation. In this paper, we will detail the mechanisms leading to the building up of the polymer
microtips by self-guiding polymerization and we will illustrate the great flexibility of this process in terms of materials,
geometry and writing wavelength. Then we will focus on some applications in optical coupling between fibers and
sensors in order to demonstrate the interest of this simple and flexible approach for polymer micro-optics
This letter provides a brief summary on early work and developments on both controlling and studying the optical
properties of resonant metal nanoparticles and reports on all progress achieved since two years. Our approach is based on
controlled nanoscale photopolymerization triggered by local enhanced electromagnetic fields of silver nanoparticles
excited close to their dipolar plasmon resonance. By anisotropic polymerization, symmetry of the refractive index of the
surrounding medium was broken: C1v symmetry turned to C2v symmetry. This approach has overcome all the
difficulties faced by scanning probe methodologies to reproduce the form of the near field of the localized surface
plasmons and provides a new way to quantify its magnitude. Furthermore, this approach leads to the production of
polymer/metal hybrid nano-systems of new optical properties.
Micro and nano-patterning of photopolymer materials was successfully carried out by using near-field irradiation
configuration. In particular, Evanescent Waves created by total internal reflection were used to induce the
photocrosslinking of an acrylate-based photopolymer sensitive at 514 nm. We demonstrate here that the thickness of the
polymer layer can be tuned from few tens of nm to several microns by controlling the irradiation conditions. The sample
was characterized by profilometry, Atomic Force Microscopy and spectroscopy.
In addition, relief gratings with adjustable fringe spacing were recorded by interferometric method. Effect of photonic
parameters on the gratings geometry is discussed. By changing the irradiation conditions, it is possible to easily obtain
patterns with different geometries, which emphasizes the high versatility of the process.
This study presents high fundamental interest in the frame of nanofabrication since it provides important information on
the effects of confinement at a nanoscale of the photopolymerization reaction. Such data are of primary importance in the
field of nanolithography since the effect of parameters such as dye content, oxygen quenching, photonic conditions can
be evaluated. Moreover, since the choice of the monomer can be done in a wide range of composition, such
nanopatterned polymers surfaces present many interests in the field of optical sensors, photonic crystals, optics, biology...
In Lippmann photography, the interference of the image with its reflection onto a mirror in contact with the photographic
emulsion allows, for each pixel of the image, the recording of Bragg gratings. Removing the mirror, processing the plate
and reading out these Bragg gratings with a white light source diffracts the very colours used for recording and thus
reproduces the images in colours. Using Lippmann photography as a data storage technique was proposed in the 1960th:
for a given pixel, and to each recording wavelength is associated one bit of data, several bits being recorded at the same
pixel. In this paper, we revisit this data storage technique and we propose and demonstrate an homodyne detection to
improve the efficiency of Lippmann data storages. The proposed homodyne geometry also presents the advantage to
simplify the architecture: the Lippmann mirror required for recording is kept in place for data retrieving. Such an
homodyne readout could also be applied to enhance the detected signals in other holographic approaches.
A flexible method of manufacturing polymer microlenses at the extremity of both single mode and multimode optical fibers has been previously developed. The procedure consists in depositing a drop of liquid photopolymerizable formulation on the cleaved fiber end and using the light emerging from the fiber to induce polymerization leading to the formation of a polymer tip. This process is highly interesting for applications in optical fiber connecting and SNOM
imaging since it is fast, highly flexible (curvature radius can range from 0.2 to 100 μm) and does not require expensive equipment.
Although the fabrication process leads to well-controlled geometrical structures, the mechanism of the polymer tip formation was not fully elucidated. In this work, we particularly focus on the photoinduced physico-chemical processes that occur during the lens formation. The effect of different parameters (irradiation time, light power, received energy, oxygen...) on the final properties of polymer tip (mechanical resistance, curvature diameter) was studied. The building up of the polymer tip was characterized by optical microscopy. This study allowed selecting the synthesis parameters leading to an improvement in the mechanical and optical properties of the polymer tip. From a fundamental point of view, this study appeared to be an interesting means to investigate the photostructuration of polymers at the micro- and nanoscales.
Organic materials are taking a growing place in the development of new materials for data technologies thanks to the potential of molecular engineering, the flexibility of available chemical compositions, the low costs..., but also because of their unique optical and mechanical properties. In this context, photopolymers present specific advantages particularly interesting for high density optical data storage, based on the possibility of structuring their linear and nonlinear optical properties with a great facility by direct optical patterning. In order to understand and control the physico-chemical aspects of the photopatterning, means of investigation at a micro and nanoscopic scales are required. Not only the 3D imaging of the object is needed, but some structural information on the material is necessary to go further in the investigation of the involved phenomena. AFM used in Pulsed Force Mode (PFM) fulfils these requirements: the PFM mode is a non-resonant mode designed to allow approach curves to be acquired along the scanning path. It thereby provides a recording of the sample topography and extends the possibilities of the prevalent contact and intermittent-contact AFM modes to a direct and simple local
characterization of adhesion and stiffness. This paper describes the principle of Pulsed Force Mode AFM and illustrates its usefulness for investigating of the photostructuration of polymer matrixes. In a first part, homogeneously irradiated films were characterized in order to demonstrate the sensibility of the PFM analysis. In particular, the PFM signal is correlated to the monomer conversion
ratio that was measured by FTIR spectroscopy. In a second step, we illustrate the potential of PFM for the investigation of photopatterned films. Holographic gratings were recorded in an acrylate-based formulation and characterized by PFM. We have successfully assigned the different areas of the film that correspond to different incident intensities. Using the information recorded on homogeneous films, it is possible to obtain an estimation of the conversion of the monomer at sub-micronic scale. Such a study is of primary importance in order to understand the mechanism leading to microstructuration and thus to optimize this process in terms of resolution.
Noticeable refractive index modulations (difference between the refractive index of high-density areas and the index of low-density areas ~8x10-3) can be created by photostructuration of acrylic films. The light pattern created by the interference of two plane waves induces inhomogeneous polymerization and mass diffusion processes, due to concentration gradients of monomer and dye, giving rise "in situ" to a structuration of the material at the microscopic scale. As the species involved in the initiation mechanism are gradually consumed as the hologram builds up, the incident dose is determined in order to reach full completion of the reaction at the end of the recording, i.e. to obtain stable gratings. This property makes photopolymers attractive materials for number of applications, especially in holography. A great advantage of these materials over other recording systems is that no chemical or heating post-treatment is required after illumination to reveal the hologram. Diffraction efficiencies of ca 80 % were obtained at 514 nm for transmission holograms with a fringe spacings between 0.2 and 5 μm. 675 mJ/cm2 corresponding to a bleaching of the dye of 85% allows non-destructive reading at an active wavelength (green light). Miscellaneous photonic parameters (chemical composition, intensity, dose...) were tested by grating recording. Taking into account all these data, improvement of the material is possible in view of data storage applications.