Summary: We report on an integrated source of twin photons at telecom wavelength operating at room temperature, in which a pump beam impinging on top of an AlGaAs waveguide generates two counterpropagating, orthogonally polarized guided modes by parametric fluorescence. This scheme allows an unprecedented flexibility in controlling the quantum properties of the emitted photons, by a simple shaping of the spatial and spectral profiles of the pump. The source versatility permits us to tailor the degree of frequency correlation and the spectrum of the emitted photons.