A differential absorption light detection and ranging (DIAL) system comprising: a plurality of laser sources, each tunable to emit a beam of light (902, 904, 906), wherein said laser sources are tuned to different wavelengths; at least one tuning controller for real time tuning and locking of each beam of light to a predetermined wavelength having a spectral line-width, wherein each beam of light is tunable during real time operation of the DIAL system; a combiner (240, 2015) for combining each beam of light to form a combined beam of light having multiple wavelengths; a transmitter for transmitting the combined beam of light toward the at least one target; a receiver for receiving light returning from the at least one target and converting returned light having multiple wavelengths to digital signals; and a processor for analyzing the digital signals to identify at least one target based on its multi-dimensional spectral characteristics; characterized in that the combiner includes: a mask including at least N apertures (932, 934, 936) with N being an integer equal to or greater than 4, each aperture configured to pass a respective beam of light at a predetermined wavelength, a focus lens, a spatial filter comprising an aperture and a collimator lens, wherein the focus lens is disposed between the mask and the spatial filter, and wherein the spatial filter is disposed between the focus lens and the collimator lens wherein the plurality of laser sources includes N lasers, N being an integer equal to or greater than 4, M of the lasers are each tuned to a wavelength that is partially absorbed by the target, M being an integer equal to or greater than 2, L of the lasers are tuned to a wavelength that is absorption-free of the target, L being an integer equal to or greater than 2, and N is equal to M+L. a plurality of laser sources, each tunable to emit a beam of light (902, 904, 906), wherein said laser sources are tuned to different wavelengths; at least one tuning controller for real time tuning and locking of each beam of light to a predetermined wavelength having a spectral line-width, wherein each beam of light is tunable during real time operation of the DIAL system; a combiner (240, 2015) for combining each beam of light to form a combined beam of light having multiple wavelengths; a transmitter for transmitting the combined beam of light toward the at least one target; a receiver for receiving light returning from the at least one target and converting returned light having multiple wavelengths to digital signals; and a processor for analyzing the digital signals to identify at least one target based on its multi-dimensional spectral characteristics; characterized in that the combiner includes: a mask including at least N apertures (932, 934, 936) with N being an integer equal to or greater than 4, each aperture configured to pass a respective beam of light at a predetermined wavelength, a focus lens, a spatial filter comprising an aperture and a collimator lens, wherein the focus lens is disposed between the mask and the spatial filter, and wherein the spatial filter is disposed between the focus lens and the collimator lens wherein the plurality of laser sources includes N lasers, N being an integer equal to or greater than 4, M of the lasers are each tuned to a wavelength that is partially absorbed by the target, M being an integer equal to or greater than 2, L of the lasers are tuned to a wavelength that is absorption-free of the target, L being an integer equal to or greater than 2, and N is equal to M+L. a mask including at least N apertures (932, 934, 936) with N being an integer equal to or greater than 4, each aperture configured to pass a respective beam of light at a predetermined wavelength, a focus lens, a spatial filter comprising an aperture and a collimator lens, wherein the focus lens is disposed between the mask and the spatial filter, and wherein the spatial filter is disposed between the focus lens and the collimator lens wherein the plurality of laser sources includes N lasers, N being an integer equal to or greater than 4, M of the lasers are each tuned to a wavelength that is partially absorbed by the target, M being an integer equal to or greater than 2, L of the lasers are tuned to a wavelength that is absorption-free of the target, L being an integer equal to or greater than 2, and N is equal to M+L.