Abstract

In this communication we study in depth the phenomenon of quadrature squeezing generated via spontaneous rotational symmetry breaking discussed for the first time in [1]. The idea can be put in short as follows. Consider a degenerate optical parametric oscillator (DOPO) tuned to the first family of transverse modes at the signal frequency, and having perfectly spherical mirrors. When pumped above threshold with a Gaussian beam and within a classical description, it is easy to show that a TEM₁₀ mode with an arbitrary orientation (measured by θ at Fig. 1) emerges at the subharmonic, hence breaking the rotational symmetry of the system in the transverse plane. Quantum effects are then quite intuitive: as any orientation is allowed, quantum noise is able to randomly rotate the generated pattern; this implies an indefiniteness in the angular orientation of the TEM₁₀ mode, what (invoking now the uncertainty principle) may lead to the perfect determination of its orbital angular momentum, which in this case coincides with the π/2 phase shifted TEM₁₀ mode orthogonal to the macroscopically generated one. Thus, perfect noise reduction is expected in the phase quadrature of this classically "empty" TEM₁₀ mode irrespectively of the pump level.

© 2009 IEEE