Transverse Fourier analysis of squeezed light in diode lasers

The transverse properties of squeezed light are studied for a number-squeezed edge diode laser working in an external-cavity configuration. Light noise is analyzed as a function of the transverse wave vector transmitted by a single slit at the focal plane of a short focal lens. Noise measurements obtained by opening the slit centered at the kx=0 position show a minimum squeezing at the slit center that increases up to the full-beam noise-compression. Noise is also measured by displacing a single slit of fixed width at the focal plane. The results of this wave-vector dependence are compared with a theory in which the slit is treated as a beam splitter for the incoming Hermite–Gaussian laser beam. A summation of the noise contributions at each wave vector cannot give the obtained result with the slit being open, which indicates a possible noise correlation of light with distinct wave vectors.