通过引入膨胀因子随光栅胶层厚度的变化函数来研究在非均匀膨胀和收缩情况下反射体全息光栅的衍射特性。根据Kamiya严格的分层计算方法，借用Lorentz-Lorenz公式，推导出了平均折射率和折射率调制度的解析表达式，据此考察了膨胀因子以定值、线性函数、非线性函数变化时光栅+1级衍射光的衍射特性，分析了平均折射率和折射率调制度在理想情况和衰减分布时对光栅角度和波长选择特性的影响程度。给出了胶层厚度及光栅周期与曝光和未曝光区域膨胀因子的函数关系，讨论了光栅衍射效率对膨胀因子变化的响应程度。结果表明，膨胀因子的非均匀分布令光栅衍射效率曲线出现非对称分布；相比于折射率调制度，光栅布拉格角度对平均折射率变化较为敏感；曝光与未曝光区域膨胀因子会影响衍射效率峰值、光栅角带宽和波带宽。该结论对反射体全息光栅曝光后水浴膨胀与脱水收缩等工艺具有理论指导意义。

Diffraction characteristics of reflection volume holographic gratings at nonuniform swelling or shrinking by introducing a function between swelling factor and the thickness of the grating layer are investigated. By means of Kamiya′s rigorous delamination-calculation method and Lorentz-Lorenz formula, the analytical expressions of the average refractive index and the modulation are derived. Accordingly, the diffraction efficiency curves of the 1st-order reflection are given when the swelling factors are constant, linear function and nonlinear function. The influences of the average refractive index and the modulation for an ideal grating or decay distribution for the nonideal grating on the angular and wavelength selectivity are analyzed. The diffraction characteristics of the grating are given when the swelling factors are unequal at the exposure area and the unexposed area, and the response degree of diffraction efficiency of the grating to the change of swelling factor is discussed. The results show that nonuniform distribution of the swelling factor causes a diffraction efficiency curve in the asymmetric profile; compared with the modulation of refractive index, the Bragg angle of grating is highly sensitive to the change of average refractive index; the swelling factors at the exposure area and the unexposed area affect the peak efficiency, the angular band range and the spectral bandwidth. The results have theoretical guiding sense for the swelling and shrinking process of the reflection volume holographic gratings.