In a wide spectral range of 400 to 1000 nm, the channeled spectra formed from the interference of polarized white light are used to extract the dispersion of phase birefringence Δn(λ) of polyethylene and cellulose triacetate (CTA) polymer sheets. The Δn(λ) of polyethylene and CTA sheets is fitted to Cauchy dispersion function with relative error of order 1.2×10 −4 and 4×10 −4 , respectively. The dispersion of group birefringence Δn g (λ) of polyethylene and CTA is also calculated and fitted to Ghosh dispersion function with relative error of order 7×10 −4 and 5×10 −4 , respectively. Furthermore, the phase and group retardations introduced by polyethylene and CTA sheets are also calculated. The amount of phase retardation confirms that polyethylene and CTA sheets can act as multiple order half and quarter wave plates working at many different wavelengths through the spectral range 400 to 1000 nm. For polyethylene and CTA sheets, a large difference between group and phase retardance is observed at a short wavelength (λ≈400 nm ), while such difference progressively diminished at a long wavelength (λ≈1000 nm ). Finally, a zero order polyethylene quarterwave plate working at 544 nm and dual wavelength CTA quarterwave plate working at 510 and 680 nm are experimentally realized.