18 November 2014 Analysis of the refractive index change of optical waveguide in LiNbO3 using a femtosecond laser
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Abstract
We used a commercially available 75 MHz regeneratively amplified laser system emitting 50 femtosecond pulses of energies up to 3nJ at a wavelength of 800 nm. All waveguides were fabricated by focussing the femotsecond pulse train polarised parallel to the x-axis to a distance of approximately 125 μm below the sample surface using a 0.65 NA, ×40 microscope objective and translating the sample along the y axis. To find the optimum waveguide fabrication parameters the translation speed was varied from 2 to 100 μm/s. We introduces a method of measuring the refractive index of optical waveguide in ten micrometer. Useing CCD to measure the two-dimensional near-field light intensity distribution of the output cross-section of the waveguide, by measuring the two-dimensional near-field light intensity distribution of the output cross-section of the waveguide can be calculated the two-dimensional distribution of refractive index of waveguides. The context detailedly gives measurement results about femtosecond laser inducing the near-field intensity of lithium niobate optical waveguide cross-section and calculations of refractive index of optical waveguide. The results show that the refractive index of waveguides showed a large central, gradually reduce and the change of refractive index in the range of 0.001. This method is of great significance to measure the optical waveguide refractive index distribution.
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Shi-han Yang, Shi-han Yang, Liang Zhang, Liang Zhang, Xue-song Lin, Xue-song Lin, Jie Feng, Jie Feng, Zi-gang Zhou, Zi-gang Zhou, Jang-jun Chen, Jang-jun Chen, "Analysis of the refractive index change of optical waveguide in LiNbO3 using a femtosecond laser", Proc. SPIE 9266, High-Power Lasers and Applications VII, 92661L (18 November 2014); doi: 10.1117/12.2071696; https://doi.org/10.1117/12.2071696
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