<p>Herein, this study introduces a simple, effective, and potentially successful approach to the preparation of polymeric composite systems using a Polyvinyl alcohol (PVA)-Polyvinyl pyrrolidone (PVP)-Polyethylene glycol (PEG) (PVA-PVP-PEG), (8:1:1) as the host polymeric blend with the inclusion of Tb(NO₃)₃-salt filler. The diffraction of X-rays (XRD), infrared spectroscopic (FTIR), Ultraviolet–visible (UV–vis) spectroscopy, and Phy-X/PSD software were utilized to analyze the modified samples’ structures, identify their optical and radiation shielding properties. The XRD patterns show the presence of Tb(NO₃)₃ phases inside the composite matrix, where adding filler causes modifications in the polymeric network’s structure for filled composite samples. FTIR analysis showed that the Tb(NO₃)₃-salt interacted with the blend’s functional groups via H-bond formation. The UV–Vis spectra analysis showed all samples, especially those loaded with 8.0 wt.% Tb(NO₃)₃-salt has the highest values for absorbance, dielectric constant, refractive index, extinction coefficient, and optical and electrical conductivity. Tauc’s formula, the ASF model, and " <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10965_2024_4219_Article_IEq1.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="55" /> </InlineMediaObject> <EquationSource Format="TEX">\({\varepsilon }_{i}-hv\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>ε</mi> <mi>i</mi> </msub> <mo>-</mo> <mi>h</mi> <mi>v</mi> </mrow> </math></EquationSource> </InlineEquation> plots were all applied to investigate optically the band gap in great detail. The values of <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10965_2024_4219_Article_IEq2.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="19" /> </InlineMediaObject> <EquationSource Format="TEX">\({\text{E}}_{\text{d}}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mtext>E</mtext> <mtext>d</mtext> </msub> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10965_2024_4219_Article_IEq3.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="19" /> </InlineMediaObject> <EquationSource Format="TEX">\({\text{E}}_{\text{o}}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mtext>E</mtext> <mtext>o</mtext> </msub> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq4"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10965_2024_4219_Article_IEq4.gif" Format="GIF" Height="12" Rendition="HTML" Resolution="72" Type="Linedraw" Width="17" /> </InlineMediaObject> <EquationSource Format="TEX">\({\text{n}}_{\text{o}}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mtext>n</mtext> <mtext>o</mtext> </msub> </math></EquationSource> </InlineEquation> have been investigated using a single oscillator model where their values were controlled by Tb(NO₃)₃- salt content<i>.</i> Using calculated gap energy, various approaches were applied to obtain the conceptual significance of the linear refractive index <InlineEquation ID="IEq5"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10965_2024_4219_Article_IEq5.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="24" /> </InlineMediaObject> <EquationSource Format="TEX">\((n)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo stretchy="false">(</mo> <mi>n</mi> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation>. 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The suggested largely doped Tb(NO₃)₃-salt composites show great promise as a CUT-OFF laser filters and attenuators in addition to being used in laser power-limiting technology. Based on our results, the sample was 8.0 wt.% Tb(NO₃)₃-salt has better gamma-ray shielding properties than the others because it has the largest Tb(NO3)3-salt concentration. The study opens a new route to fabricate Tb(NO₃)₃/(PVA-PVP-PEG) polymeric composites with superior optical properties.</p>