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Broadband quasi-phase-matched wavelength converters.

机译：宽带准相位匹配波长转换器。

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摘要

This thesis proposes new concepts in broadband optical frequency conversion in quasi-phase matched guided-wave devices. Quasi-phase matching (QPM) using domain-inverted gratings in nonlinear materials such as lithium niobate (LN) by reversing the sign of the second-order nonlinear coefficient, has been successfully applied in recent years to take advantage of the highest nonlinear coefficient for second harmonic generation (SHG), sum frequency generation (SFG) and difference frequency generation (DFG). Nevertheless, the periodic quasi-phase matched structure has a negative impact by limiting the bandwidth of frequency up-conversion.;The modified single-pass and double-pass configurations are also proposed in this dissertation lead to bandwidth broadening and efficiency enhancement of waveband wavelength converters based on quasi-phase matched cascaded sum frequency generation and difference frequency generation (SFG + DFG) in LN waveguides. It has been shown that increasing the pump wavelength difference in cascaded SFG + DFG devices, enhances the bandwidth, but with noticeable variation in efficiency response for larger pump wavelength differences, leading to uneven equal-input-power signal channel conversion.;Two different solutions have been suggested in this thesis to solve the problem in both single-pass and double-pass configurations, namely, detuning of a pump wavelength, and using a few-section step-chirped grating (SCG). It is shown that, if a pump wavelength is increasingly detuned, the SFG and DFG phase-mismatch decreases differently which leads to flattening of the conversion efficiency response. Alternatively, the period of a few-section SCG can also be increased slightly to arrive at a similar result.;The role of these schemes is very important as wide waveband converters can be used for the wavelength division multiplexing (WDM) systems, in which the 3-dB bandwidth of the device should be broad enough to cover the 1.55 mum optical window. For this purpose, the pumps are set at wavelengths out of the optical window which is 75-nm wide, whilst we obtain flat responses with high conversion efficiency. For different single-pass and double-pass configurations using pump detuning or the SCG, design diagrams for the choice of low-loss waveguide length, and the assignment of pump powers of to achieve the desired efficiency, ripple and bandwidth are presented. (Abstract shortened by UMI.);In this dissertation, it has been demonstrated for the first time that using the technique of apodization with chirped gratings, the bandwidth of frequency doublers based on SHG in lithium niobate waveguides can be broadened at will, and the ripple damped out ( +/-0.05dB) to be low enough so as to be considered almost flat. A consequence of this technique is that the guided wave device may be used as a source over a wide unregulated temperature range, for the first time. It has been shown that using the apodized step-chirped gratings (ASCG) approach, the wide spectral conversion efficiency profile (> 50 nm) is suitably controllable. The large domain-widths and chirp-steps ease device manufacture. The impact of this design is clearly very high as firstly, this broadband wavelength converter can be used for variable waveband wavelength conversion in future all-optical networks, as the device based on the cascaded second harmonic generation and difference frequency generation (SHG + DFG), should be a broadband frequency doubler. Secondly, for displays it may lead to the realization of high-efficiency three-color frequency converters that do not change in intensity, even without the use of temperature control. However, the SHG efficiency of an ASCG device is lower than that of the uniform grating with the same length. It is shown for the first time that it is possible to increase the efficiency of an ASCG device for broadband frequency doubling, by using a tight confinement in small-effective-cross-section low-loss waveguides, and with the resonance of fundamental harmonics in a singly pump-resonance waveguide.
机译：本文提出了准相位匹配波导装置宽带光频率转换的新概念。近年来，通过反转二阶非线性系数的正负号，在诸如铌酸锂（LN）的非线性材料中使用域反转光栅的准相位匹配（QPM）已成功应用，以利用最高非线性系数的优势。二次谐波生成（SHG），和频生成（SFG）和差频生成（DFG）。然而，周期性的准相位匹配结构会限制频率上变频的带宽，但会产生负面影响。论文还提出了改进的单通和双通配置，可实现带宽的扩展和波段波长效率的提高。 LN波导中基于准相位匹配的级联和频生成和差频生成（SFG + DFG）的转换器。已经表明，增加级联SFG + DFG器件中的泵浦波长差，可以增加带宽，但是对于较大的泵浦波长差，效率响应会出现明显变化，从而导致均等输入功率信号通道转换不均匀。两种不同的解决方案本文提出了解决单通和双通配置中的问题的方法，即对泵浦波长进行失谐，并使用几节阶跃chi光栅（SCG）。结果表明，如果泵浦波长越来越失谐，则SFG和DF​​G的相位失配会以不同的方式减小，从而导致转换效率响应趋于平坦。或者，也可以将几段SCG的周期略微增加，以获得相似的结果。这些方案的作用非常重要，因为宽带转换器可以用于波分复用（WDM）系统，其中设备的3 dB带宽应足够宽，以覆盖1.55毫米的光学窗口。为此，将泵浦设置在光学窗口之外的波长（75纳米宽），同时我们获得具有高转换效率的平坦响应。对于使用泵失谐或SCG的不同单通和双通配置，给出了用于选择低损耗波导长度的设计图，以及实现理想效率，纹波和带宽的泵浦功率分配。 （本文由UMI缩短。）；本文首次证明，利用chi光栅切趾技术可以随意扩大铌酸锂波导中基于SHG的倍频器的带宽，并且纹波衰减（<+/- 0.05dB）足够低，以至于几乎被认为是平坦的。该技术的结果是，导波装置首次可在较宽的未调节温度范围内用作源。已经表明，使用变迹步进step光栅（ASCG​​）方法，可以适当地控制宽光谱转换效率曲线（> 50 nm）。大的域宽度和chi步简化了设备制造。这种设计的影响显然是非常高的，首先，这种宽带波长转换器可用于未来的全光网络中的可变波段波长转换，因为该设备基于级联的二次谐波生成和差分频率生成（SHG + DFG） ，应该是宽带倍频器。其次，对于显示器，即使不使用温度控制，也可能导致强度不变的高效三色变频器的实现。然而，ASCG器件的SHG效率低于相同长度的均匀光栅的SHG效率。首次表明，通过在小有效横截面低损耗波导中使用严格的限制，并在谐振中产生基本谐波，可以提高ASCG器件的效率，从而实现宽带倍频。单泵谐振波导。

著录项

  • 作者

    Tehranchi, Amirhossein.;

  • 作者单位

    Ecole Polytechnique, Montreal (Canada).;

  • 授予单位 Ecole Polytechnique, Montreal (Canada).;
  • 学科 Engineering Electronics and Electrical.
  • 学位 Ph.D.
  • 年度 2010
  • 页码 148 p.
  • 总页数 148
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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