For quantum biomicroscopy, light sources need to provide a reliable signal at low intensity levels with a high rate generation in the near-infrared region. To develop this light source, we investigated the abilities of generating ultrabroadband two-photon states in the near-infrared in a periodically poled lithium niobate (LiNbO3) nanowaveguide with different geometrical cros-section and pump wavelength. Using modeling and numerical calculations the optimal nanowaveguide parameters providing the maximum width of the spectrum of two-photon states $∼$ 180 THz under the pump wavelength about 1.0 $μ$m were determined.