A system and method are provided for characterizing a laser using a diffraction grating. The system includes a lens that projects diffraction patterns from the diffraction grating as an image of diffraction peaks onto a plane. Optical sensors then sense the diffraction peaks. A processor connected to the optical sensors applies the laser characterization method to determine the laser wavelength, irradiance and angle of incidence. In the method, the processor obtains the diffraction peak measurements from the optical sensors and applies a transform to arrange the diffraction peaks into a grid of regularly spaced peaks. The processor then applies convolution kernels to analyze the grid of regularized peaks to determine a wavelength, irradiance and angle of incidence of the laser.