Quantum Fluctuation of Ultrashort Pulsed Light in a Semiconductor Waveguide at Just Below Band-gap Energy

The quantum noise of 1-ps pulsed light is theoretically investigated in a semiconductor waveguide at just below the band-gap energy, where Kerr effects with n2 < 0 induce nonlinear negative-ω chirping, which is useful for alternative devices to a phase conjugator. Our calculation shows that Kerr effects with n2 < 0 squeeze quantum noise below the standard quantum limit (SQL), leading to a nonlinear increase in the phase-noise with increasing a pulse energy while keeping the whole photon-number noise of light constant, similar to the case with n2 > 0. However, this nonlinear negative-ω chirping produces a clockwise tilted ellipse of the quantum noise distribution for squeezed light in phase space, unlike the case with n2 > 0. In addition, we estimate that spatial modal area modification caused by self-defocusing with n2 < 0 results in a reduced degree of squeezing of light with diminished phase noise. KCI Citation Count: 1