Generation of Ultrabroad Optical Sideband by Domain-Inversed Waveguide-Type Electro-Optic Modulators and Applications

本研究的目的是研制一种新型的电光调制器，它与域倒置结构和光波导结构相结合，产生超宽带光学边带，并探索它们的新应用。结果，我们成功地实现了波分复用器(WDM)系统中非常有用的频率梳光源、移频器、单边带(SSB)调制器和紧凑集成的飞秒光脉冲发生器，采用这种波导结构使大幅度降低驱动功率成为可能。首先，设计了用于超宽带产生的电极和光波导的长度和宽度，并将其应用于光源…更多的是在WDM系统中，这需要很高的调制效率。结果，高效的连续波调制和宽连续波光边带的产生成为可能。域反转区域的位置漂移等同于调制射频信号的相移，因此，可以利用单个射频信号来实现正、余弦调制。利用这一效应，我们构造了一种新型的单边带调制器，该调制器具有简单的波导结构，并成功地验证了它的单边带工作，由通常的相位调制得到的边带具有类似贝塞尔函数的幅度并且缺乏平坦性。这对于频率梳发生器来说是个问题。提出了一种新的空间调制器--平坦分布的空间分离边带产生器，它是在周期域倾斜倒置结构产生的行位相光栅上加入空间形变而构成的。此外，我们还成功地采用了非周期域倒置结构来构成超宽带调制器。该器件的调制带宽(-1分贝)比普通行波电光调制器宽6倍。此外，我们还在一个LiTaO_3针尖上集成了用于超宽带产生的相位调制器和群延迟色散电路。在初步实验中，我们利用该集成器件成功地将连续光波直接转换为皮秒脉冲。较少

The purpose of this study is to develop new kinds of electro-optical modulators together with domain inverted structure and wave-guide structure and to generate ultra-broad optical sideband and to find out new application of them. As results, we succeeded in materialization of the frequency comb generator which is very useful as light sources in the wavelength division multiplexing (WDM) system, of the frequency shifter, a single sideband (SSB) modulator and the compact integrated femtosecond optical pulse generators.Adopting the waveguide structure makes it possible to decrease driving electric power drastically. The geometrical spatial modification of the domain-inverted structure makes multipath parallel operation of the modulator or various types of spatial light modulation possible.First of all, the length and the width of the electrode and the optical waveguide were devised for the ultra-broad sideband generation, the frequency comb generator, and application to the light source … More in the WDM system, which require high modulation efficiency. As a result, efficient cw modulation and generation of broad cw optical sidebands became possible. The position shift of domain inverted area yields equivalently the phase shift of modulation rf signals, therefore, we can get sin and cos modulation by single rf signal. Using this effect, we constructed new kind of SSB modulator with simple wave-guide structure and succeeded in confirmation of its SSB operation.The sidebands obtained by a usual phase modulation have Bessel function-like amplitude and lack in flatness. It is problem for frequency comb generator. We proposed the new spatial modulator, spatially separated sideband generator with flat distribution, which is constructed by adding the spatial deform to traveling phase grating produced by tilted periodic domain inverted structure. Moreover, we succeed in the composition of the ultra-broadband modulator by adopting the non-periodical domain inverted structure. The modulation bandwidth (-1 dB) of this device was estimated to be six times wider than that of the normal traveling-wave EO modulator. In addition, we integrated the phase modulator for the ultra-broad sideband generation and the group delay dispersion circuit on one LiTaO_3 tip. In preliminary experiment using this integrated device we succeeded in direct conversion from the continuous light-wave into the picosecond pulses. Less