Abstract

The semiconductor laser is potentially a source of ultra wideband squeezed light. In fact, the widest bandwidth over which amplitude-noise reduction has been observed to date has been achieved with a diode laser.¹ In the conventional theory of squeezed-state generation from a semiconductor baser, the squeezing bandwidth is limited practically by the relaxation-oscillation frequency (~10s GHz) and ultimately by the cavity resonance frequency (~100 GHz). It was recently proposed that the effects of Coulomb blockade should limit the current-noise suppression in even macroscopic p-i-n junctions.³ If the optical quantum efficiency of a junction is high, then the absence of current noise suppression should be observable from a measurement of the optical field. In an attempt to clarify the proper noise model of a p-n junction, we have measured the bandwidth over which the external field amplitude fluctuation of a semiconductor laser is reduced to below the standard quantum limit. These systematic measurements of the squeezing bandwidth also permit comparison (for the first time to our knowledge) of the competing mechanisms for band width reduction.

© 1994 Optical Society of America