Optical Modes in a Rectangular VCSEL Resonator With Properties of Both Gaussian and Fourier Modes

We present the optical modes of a vertical-cavity surface-emitting laser resonator with a large Fresnel number in one direction, and a small Fresnel number in the other direction. The modes show properties of both the well-known Gaussian modes in lasers with a small Fresnel number and the modes of the Fourier type, which have been observed in lasers with a large Fresnel number. Also simultaneous oscillation of two modes near threshold and a higher-order mode in the direction of the small Fresnel number is observed experimentally.