石英光纤中二次非线性级联波长转换的理论分析

提出了利用周期性热及电场诱导D型光纤光栅的二次非线性级联(χ⁽²⁾∶χ⁽²⁾)，实现在波分复用网中波长转换的方法，并进行了理论分析.推导出χ⁽²⁾ ∶χ⁽²⁾的耦合模方程，得出了小信号条件下转换产生光波的场强振幅和 功率，以及转换效率η的解析式，该式与数值计算相吻合.解析式和数值结果都表明，在近 似满足相位匹配条件下，η与抽运光功率平方、光栅总长度L和二次非线性系数d的四次方分 别成对数关系.计算结果表明，这种光纤光 关键词： 石英光纤 二次非线性 级联 波长转换 光纤光栅 诱导

THEORETICAL ANALYSIS OF WAVELENGTH CONVERSION FOR CASCADING SECOND-ORDER NONLINE ARITIES IN SILICA FIBER

A novel wavelength conversion method for wavelength division multiplexing(WDM) n ets by use of cascaded second-order nonlinearities (χ⁽²⁾∶χ⁽²⁾ ) in D-fiber grating after periodically thermal/electric-field poling is p roposed,and is theoretically analyzed for the first time.The coupled mode equati ons of the χ⁽²⁾∶χ⁽²⁾ nonlinearities are derived,and the analytic expressions for the electric-field intensity amplitude of the conversi on light waves and conversion efficiency η are obtained under the small signal condition,which are well consistent with numerical calculations.Both analytic ex pressions and numerical results show that,under the suitabl phase-matching condi tion,η is proportional to the logarithm of the square of pump light power,and the 4th power of the grating length L & second-order nonlinearity d.The calculat ed results also show that the wavelength conversion efficiency η and conversion bandwidth Δλ of over-17dB and 120nm respectively can be reached with this fib er grating.With the increase of L,η increases quickly white Δλ decreases quic kly.The results of simulated calculation and theoretical analysis show that the cascaded χ⁽²⁾∶χ⁽²⁾ process is different from that of qu asi-phases-matched difference-frequency-generation.