Nonlinear optical properties of photoresists for projection lithography

Optical beams are self-focused and self-trapped upon initiating crosslinking in photoresists. This nonlinear optical phenomenon is apparent only for low average optical intensities and produces index of refraction changes as large as 0.04. We propose using the self-focusing and self-trapping phenomenon in projection photolithography to enhance the resolution and depth of focus

Electric-field multiplexing/demultiplexing of volume holograms in photorefractive media

We propose a new method of volume hologram multiplexing/demultiplexing in noncentrosymmetric media. Volume holograms may be multiplexed by tuning the material parameters of the recording medium (such as refractive index or lattice parameters) while keeping the external parameters (wavelength and angles) fixed. For example, an external dc electric field alters the index of refraction through the electro-optic effect, effectively changing the recording and reconstruction wavelengths in the storage medium. Then the storage of holograms at different fields, hence different indices of refraction, is closely related to wavelength multiplexing. We demonstrate this concept in a preliminary experiment by electrically multiplexing two volume holograms in a strontium barium niobate crystal

Selective page-addressable fixing of volume holograms in Sr0.75Ba0.25Nb2O6 crystals

We demonstrate selective fixing of volume holograms in photorefractive media. Each holographic page may be fixed individually and overwritten without destroying the other fixed pages. We present experimental results describing this process in Cr-doped Sr0.75Ba0.5Nb2O6 at room temperature, with hologram lifetimes exceeding 100 days during continuous readout with an intense beam (1 W/cm^2)

Optical and electrical Barkhausen noise induced by recording ferroelectric domain holograms

Ferroelectric domain gratings with periods of the order of an optical wavelength are induced in strontium barium niobate by photorefractive space-charge fields. We measure the Barkhausen noise in current and diffraction efficiency while optically recording domain gratings and show that the two are strongly correlated in time. Significant random depolarization occurs under high-intensity illumination. We deduce the kinetics of the domain inversion process from the shape of the current transients

Self-focusing and self-trapping of optical beams upon photopolymerization

We demonstrate theoretically and experimentally that optical beams are self-focused and self-trapped upon initiating photopolymerization. This unique nonlinear optical phenomenon is dependent on the optical exposure and produces permanent index-of-refraction changes larger than 0.04. The resulting nonlinear wave equation is shown to be nonlocal in time and displays self-trapped solutions only for sufficiently low average optical intensities

All-fiber zero-insertion-loss add-drop filter for wavelength-division multiplexing

We developed and fabricated an all-fiber add–drop filter by recording a Bragg grating in the waist of an asymmetric mode converter–coupler formed by adiabatic tapering and fusing of two locally dissimilar, single-mode optical fibers. The insertion loss of the device was ~0.1 dB. A narrow spectral bandwidth (90%) were also demonstrated. In addition, the filter was polarization independent

Part I. Optically induced, ferroelectric domain gratings in photorefractive crystals and applications to nonlinear optics. Part II. Self-focusing and self-trapping of optical beams upon photopolymerization and applications to microfabrication

This thesis explores the application of two distinct nonlinear optical phenomena, the photorefractive effect and photopolymerization, to optically generate microstructures with feature sizes on the order of optical wavelengths. First, we have found that in certain photorefractive crystals, the photogenerated space charge field dynamically aligns ferroelectric domains. This is demonstrated by the observation of Barkhausen noise linked to the formation of domain gratings. Domain gratings are recorded with spatial periods on the order of optical wavelengths, which we use for quasi-phase matched second harmonic generation and holographic data storage. The second part of this thesis explores the nonlinear optical response accompanying photopolymerization. In some photopolymers, the crosslinking of polymer chains induces a significant increase in the index of refraction in the exposed region. This index perturbation acts as a lens which subsequently focuses down the input light wave. We observe self-focused and self-trapped optical beams upon photo-induced crosslinking of a liquid monomer. In the case of self-trapping, the inherent diffraction of the optical beam is exactly balanced by self-focusing, so the diameter of the beam does not change as it propagates through the medium. Most importantly, this waveguiding generates solid polymer microstructures in the illuminated region, which can be used to fabricate micro-electromechanical systems and optical interconnects