Effect Of Applied Electric Field And Temperature On LiNbO₃ Device

As an crucial device in Integrated Optics field, LiNbO₃ crystal is outstanding. Ti:LiNbO₃ have relatively low transmission loss, stable electro-optic coefficient and excellent transmission characters. Ti:LiNbO₃ waveguides sometimes work under applied electronic field, thus it is critical to clarify the effect that applied electronic field caused on transmission characters of waveguides. This thesis mainly discuss transmission characters of congruent Ti:LiNbO₃ optical waveguides under flat field in space. The primary works are listed below:1. Realization of end coupling system. Characterize the corelation between electronic field intensity and transmission characters of waveguide. To begin with, applied the dynamometer to measure the output light intensity under vary electronic field intensity, we discovered this phenomena: the electronic field intensity ranged from 0 to 150V/mm, with the light intensity reduced from-30 d Bm to 0. At this point, the output light intensity can recovered to-30 d Bm with an adjustment of fiber position vertically. Then we used an CCD to view the near-field patterns of the Ti: LiNbO₃ waveguide under electronic field, we discovered this phenomena: the electronic field intensity ranged from 0 to 150V/mm, with the intensity of mode pattern reduced continuously until disappeared. At this point, the mode patterns can reappear with an adjustment of fiber position vertically. The field distribution of waveguide remained comply with Gauss distribution in width, and hermitian Gauss distribution in depth. Analysis and summarize the phenomena. With the effect of electronic field, the field pattern of the optical waveguide have a translation in the direction parallel to electronic field, but its mode size and distribution pattern remain unchanged. This translation will cause the increase of coupling loss, the output light intensity dropped consequently. The adjustment of fiber position vertically can recover the matching degree between the fiber and waveguide, thus boosting the output light intensity.2. Build a measuring system to study the effect of the temperature on the Er³⁺ ions UC fluorescence intensity.Analysising the 980 nm upconversion emission spectrogram of Er³⁺ doped lithium niobite crystas,we can conclude that the temperature effect on the UC fluorescent intensities shows that both peak and integrated UC fluorescent intensities decrease with the temperature rise of 57 °C from the 21 °C,as to the 530, 560 and 670 nm emission UC fluorescent intensities drop by 26%, 42% and 34%, respectively.Morever,it may be also applicable to design the temperatre sensor utilzing the emission of the 560 and 670 nm emission.Further experiments demonstrate the relationship between the mid-infrared emission intensities of Er³⁺ doped lithium niobite crystals and the variety of temperature,discovering that the peak emission intensities reduce by nearly 78% with the sample temperature rise of 54°C from 24 °C, implying that the Er³⁺ doped crystals possess a larger temperature sensitivity.Therefore,it is more feasible to fabricate the temperature sensor comparing to the green induced UC fluorescence.According to results above, the change of electronic field intensity will cause the light to transmiss or be restrained, which is similar to the optical switch theory. As a result, there is a possibility that we can use this phenomena to make an optical switch. The benefit of this new type of optical switch is that we can use it in a low electronic field, 150V/mm. In conclusion, this discovery is beneficial to further fabrication optical switches.