Fields of apertured polychromatic laser beams with Gaussian and Hermite–Gaussian transverse modes

Starting from the Huygens–Fresnel diffraction integral, the field expressions of apertured polychromatic laser beams with Gaussian and Hermite–Gaussian transverse modes are derived. Influence of the bandwidth on the intensity distributions of the laser beams is analyzed. It is found that when the bandwidth increases, the amplitudes and numbers of the intensity spikes decrease and beam uniformity is improved in the near field and the width of transverse intensity distribution of the apertured beams decreases in the far field. Thus, the smoothing and narrowing effects can be achieved by increasing the bandwidth. Also, these effects are found in the laser beams with Hermite–Gaussian transverse modes as the bandwidth increases.