Yb:CaGdAlO4　(Yb:CALGO)　single　crystals　having　a　series　of　Yb3+　concentrations　(0.5,　1.7,　2.5,　5.0,　7.2,　and　8.0　at%)　were　grown　using　the　Czochralski　method.　X-ray　powder　diffraction　(XRD),　polarized　absorption,　fluorescence　spectra,　and　Raman　spectra　were　measured　for　the　synthesized　crystals　to　investigate　the　influence　of　the　doping　concentration　of　Yb3+　on　the　structure　and　spectral　properties.　The　results　indicate　that　Yb3+　doping　concentrations　within　the　tested　range　induce　a　negligible　change　in　the　structure　but　a　significant　change　in　the　absorption　and　fluorescence　features.　Both　polarized　absorption　and　emission　intensity　in　the　π　and　σ-polarization　increase　with　the　increment　of　Yb3+　concentration.　The　fluorescence　lifetimes,　determined　using　the　powder　concentration　dilution　method,　varied　from　0.454　ms　to　0.527　ms.　Various　spectral　cross-sections　of　Yb:CALGO　crystals　were　calculated　and　analyzed.　Moreover,　within　the　examined　range,　Yb3+　concentration　exhibits　negligible　impact　on　the　positions　of　the　primary　peaks　observed　in　the　Raman　spectra.　However,　a　notable　intensity　difference　was　observed　at　311　cm−1　in　the　Raman　spectra　measured　along　the　a-　and　c-directions,　which　can　be　attributed　to　variations　in　the　linkage　of　AlO45−　groups.　This　work　provides　a　basis　for　the　Yb:CALGO　femtosecond　laser　experiments　by　optimizing　the　Yb3+　concentrations.　©　2025　The　Royal　Society　of　Chemistry.