Surface enhanced resonant Raman scattering (SERRS) signals are enhanced by confining the scattering to the core of a hollow core microstructured optical fiber. An analyte solution of rhodamine 6G adsorbed on colloidal silver was used. This solution filled both the core and cladding of the fiber. It was found that SERRS signals could be collected from the solution in the fiber beyond the detection limit of an equivalent free space system.
Photoinduced depoling in a crosslinked side-chain polyurethane-disperse red 19 thin film is investigated. Using an electro-optic grating modulator, we have investigated the electro-optic coefficients and depoling rates of the poled polymer films as a function of incident fluence at different wavelengths from 543 to 795 nm. Our experiments showed that when the incident wavelength approaches the absorption peak of the nonlinear optical chromophore attached to polymer backbone, the depoling effect becomes more and more severe. The photoinduced relaxation rate increased approximately 5 orders in magnitude from 670 nm to 543 nm. The photoinduced depoling was observed even at wavelengths 200 nm away from the peak absorption wavelength of the chromophore. A polarization microscope showed that chromophores were randomized and rotated by the excitation laser beams after exposure. However, no significant photoinduced depoling was detected during the time span of the measurement of 795 nm near infrared wavelength which is approxiamtely 320 nm away from the absorption peak.
To demonstrate the feasibility of integrating polymer electro-optic devices on Si circuitry, we have vertically integrated a demonstration slab phase modulator on nonplanar VLSI circuitry. Optical loss measurements for waveguides fabricated on planarized circuits demonstrate that more practical devices like channel phase and Mach-Zehnder amplitude modulators can easily be integrated onto the circuits.
A novel measurement technique for characterizing both the real and imaginary parts of the electro-optic r<SUB>33</SUB> and r<SUB>13</SUB> coefficients of in-plane poled polymer thin films is proposed and demonstrated. Efficient in plane poling with applied DC fields up to 200 V/micrometers was achieved. A r<SUB>33</SUB> of 12.5 pm/V at the 1.3 micrometers wavelength was measured for a polyurethane disperse red 19 polymer. 'Push-pull' modulation was demonstrated.
Nonlinear optical properties of 3, 4, 9, 10-perylenetetracarboxylic dianhydride thin films grown by ultra-high vacuum process of organic molecular beam deposition are characterized by self-diffraction method. We observe a large diffraction efficiency (approximately 10<SUP>-4</SUP>) from a micron thick film and attribute the nonlinearity to a thermal shift in the excitonic absorption feature or free carrier effects.
We report our study of a new sol-gel polymer for nonlinear optics applications. An amino- sulfone dye chromophore was covalently incorporated into a sol-gel network and each chromophore was firmly anchored at both ends via nine possible crosslinking sites. After corona poling and thermal curing at elevated temperatures using a new kind of `step' poling profile, a d<SUB>33</SUB> of 27 pm/V was measured at the 1.06 micrometers fundamental wavelength. Long term stability at 100 degree(s)C and short term stability at 200 degree(s)C were demonstrated. A phenomenological explanation for the behavior of the dynamic SHG signal to our `step' profile is also proposed.
A simple and easy method to study the dispersion of electro-optic coefficients of poled second- order nonlinear optical polymer films is presented. Phase grating type electro-optic modulators were used to measure the relative electro-optic effects at different wavelengths. The grating structures were formed by either etching a grating in the nonlinear polymer thin films or defining a transparent electrode on top of a uniform polymer film. When an AC voltage is applied to the electrodes, the diffraction efficiency of the grating is modulated by the small index modulation. The measurement of the electro-optic response can be carried over a large wavelength range, even deep into the absorption band of the material due to the short interaction length of the optical beam and the polymer thin film. The grating modulation method uses a single optical beam in a transmission arrangement which requires little optical alignment and no polarization optics. With a properly designed electrode, the grating modulator can also be used in measuring the electro-optic coefficient, r<SUB>13</SUB>, of the poled polymer films. Other measurement applications such as monitoring temporal, thermal, and photo-excitation stability are discussed.