8 research outputs found
Theoretical and Experimental Study of the Nonlinear Optical and Dispersive Properties of Conventional and Photonic Crystal Fibers
No full textThe early use of the induced grating autocorrelation (IGA) method to measure the nonlinear refractive index of single mode fibers utilized 50-70 ps pulses at 1064-nm and required only 15-20 m lengths of fiber. Exotic fibers, such as photonic crystal fibers (PCFs), are extremely expensive and limit many applications to a few meters. Therefore, a practical measurement of the nonlinear coefficient for such exotic fibers requires a technique sensitive to shorter fiber lengths (< 5 m). To reduce the fiber length requirements, the IGA technique must use shorter pulses. In this work, a new mathematical description was developed for the IGA technique that is applicable to pulses as short as 100 fs. This model includes effects such as dispersion, self-phase modulation, stimulated Raman scattering, intra-pulse Raman scattering and self-steepening. The model was used to investigate pulse propagation at three pulsewidths: 50 ps, 2 ps, and 120 fs. The model predicted the sensitivity of IGA measurements to dispersive and nonlinear effects at these pulsewidths. The numerical model led to the successful experimental determination of both the dispersion and nonlinear coefficients of a 15m long single-mode fiber using a 2 ps Ti: sapphire laser at 800 nm. The nonlinear coefficient for several PCFs (a 30 cm long highly nonlinear PCF and two large mode area PCFs of 4.5 m and 4.9 m long) were also successfully measured with excellent numerical fits using this new IGA model
Theoretical and Experimental Study of the Nonlinear Optical and Dispersive Properties of Conventional and Photonic Crystal Fibers
No full textThe early use of the induced grating autocorrelation (IGA) method to measure the nonlinear refractive index of single mode fibers utilized 50-70 ps pulses at 1064-nm and required only 15-20 m lengths of fiber. Exotic fibers, such as photonic crystal fibers (PCFs), are extremely expensive and limit many applications to a few meters. Therefore, a practical measurement of the nonlinear coefficient for such exotic fibers requires a technique sensitive to shorter fiber lengths (< 5 m). To reduce the fiber length requirements, the IGA technique must use shorter pulses. In this work, a new mathematical description was developed for the IGA technique that is applicable to pulses as short as 100 fs. This model includes effects such as dispersion, self-phase modulation, stimulated Raman scattering, intra-pulse Raman scattering and self-steepening. The model was used to investigate pulse propagation at three pulsewidths: 50 ps, 2 ps, and 120 fs. The model predicted the sensitivity of IGA measurements to dispersive and nonlinear effects at these pulsewidths. The numerical model led to the successful experimental determination of both the dispersion and nonlinear coefficients of a 15m long single-mode fiber using a 2 ps Ti: sapphire laser at 800 nm. The nonlinear coefficient for several PCFs (a 30 cm long highly nonlinear PCF and two large mode area PCFs of 4.5 m and 4.9 m long) were also successfully measured with excellent numerical fits using this new IGA model
Oxygen-dependent laser inactivation of murine norovirus using visible light lasers
No full textAbstract Background Previous work indicated that an ultrashort pulse (USP) 425 nm laser is capable of inactivating murine norovirus (MNV: Virol. J. 11:20), perhaps via an impulsive stimulated Raman scattering (ISRS) mechanism, and does not substantially damage human plasma proteins (PLOS One 9:11). Here, further investigation of virus inactivation by laser light is performed. Methods In this study, we evaluate whether inactivation of MNV is specific to the USP wavelength of 425 nm, or if it occurs at other visible wavelengths, using a tunable mode-locked Ti-Sapphire laser that has been frequency doubled to generate femtosecond pulses at wavelengths of 400, 408, 425, 450, 465, and 510 nm. Continuous Wave (CW) lasers are also applied. Singlet oxygen enhancers are used to evaluate the sensitivity of MNV to singlet oxygen and oxygen quenchers are used to evaluate effects on virus inactivation as compared to untreated controls. Results > 3 log10 inactivation of MNV pfu occurs after irradiation with an average power of 150 mW at wavelengths of 408, 425 or 450 nm femtosecond-pulsed light for 3 h. Thus results suggest that the mechanism by which a laser inactivates the virus is not wavelength-specific. Furthermore, we also show that irradiation using a continuous wave (CW) laser of similar power at 408 nm also yields substantial MNV inactivation indicating that inactivation does not require a USP. Use of photosensitizers, riboflavin, rose bengal and methylene blue that generate singlet oxygen substantially improves the efficiency of the inactivation. The results indicate a photochemical mechanism of the laser-induced inactivation where the action of relatively low power blue laser light generates singlet oxygen. Conclusion Results suggest formation of short-lived reactive oxygen species such as singlet oxygen by visible laser light as the cause of virus inactivation rather than via an ISRS mechanism which induces resonant vibrations
