Study and Fabrication of Periodically Poled Lithium Tantalate Crystal Fiber
Date Issued
2007
Date
2007
Author(s)
Sun, De-Hao
DOI
zh-TW
Abstract
Wavelength converters based on nonlinear optics is one of the most important techniques in high efficienct optical communication systems. For fiber communication, especially when the capability of transmission is over 10 Gb/s, all-optical wavelength converters have advantages than traditional electrical-optical-electrical converters. Besides, blue/green light generation due to wavelength conversion plays a great role in many applications, such as high-density-optical storage, display, biomedical analysis, and under-water communications. Various applications can be achieved by designing quasi-phase-matching (QPM) period no nonlinear-optical crystals. The key factors to achieve high conversion efficiency are crystal quality and pitch uniformity.
In this thesis, periodically poled Lithium Tantalate crystal fiber (PPLTCF) for wavelength conversion was grown by laser heated pedestal (LHPG) growth method with additional high-electric field bias. During the process of fabrication, parameters of applied E-field were optimized in order to achieve domain inversion with high uniformity and process automation. To examine domain pitch of PPLTCF, a confocal second harmonic (SH) microscopy was used. The analyzed SH pattern showed that the 21.33-um domain pitch had only a 3.2% deviation from the 20.67-um designed pitch. It was unexpected that the SH sigal at the domain interface is stronger than that in the +Z and –Z domains. To examine this, a randomly distributed polarization model was established, and compared with the experimental result with good agreement.
In the optical experiment, the SH signal was measured to be 0.77 uW at 1524.24-nm fundamental wavelength with an 100-mW pump power. Accordingly, a PPLTCF SHG device made by LHPG method was experimentally demonstrated. Besides, a wavelength-conversion design for generating tunable blue/green light was proposed by means of self-cascaded SH generation and Sun frequency generation effect. Based on the nonlinear-chirped-grating design, the simulation showed an extended 225.25 nm 3-dB bandwidth for fundamental wavelength. It corresponds to a blue/green bandwidth of 75.17 nm in the range from 460.25 nm to 535.42 nm. With the same crystal length, the spectrum width was broader and more flattened by nonlinear chirp than that by linear chirp.
Subjects
鉭酸鋰
非線性光學
波長轉換
頻率轉換
極化反轉
共焦
倍頻顯微
週期漸變
Litao3
PPLT
Nonlinear optics
wavelength conversion
frequency conversion
domain inverse
poling
SH microscopy
confocal
second harmonic
fiber grating
chirp
Type
thesis
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