Higher order transverse modes of an unstable-cavity laser

We present measurements of the higher order transverse modes of an unstable-cavity HeXe gas laser. We have studied the one-dimensional strip-resonator modes and the two-dimensional square- and circular-resonator modes. The experimental intensity profiles showed generally good agreement with theoretical profiles based upon virtual-source diffraction theory. We also measured the quantum-limited linewidths and excess-noise factors of several of these modes.