Soliton squeezing at the gigahertz rate in a Sagnac loop

Generation of squeezed vacuum pulses at 810 nm using a 40-cm-long optical fiber

We experimentally demonstrate the generation of a squeezed vacuum pulse at 810 nm with a fiber polarization interferometer. During femtosecond laser pulse propagation through an optical fiber in the normal dispersion regime, only self-phase modulation within a short length contributes to pulse squeezing since the laser pulse is immediately broadened. Guided acoustic-wave Brillouin scattering (GAWBS) noise that increases in proportional to the fiber length is also lower with shorter fibers. Consequently, a maximum noise reduction of 2.1 dB (4.8 dB when corrected for losses) is obtained using a 40-cm-long single mode optical fiber.

Entangled quantum nonlinear Schrödinger solitons

Considered as a multipartite quantum system, time-multiplexed nonlinear Schrödinger solitons after collision are rigorously proved to become quantum entangled in the sense that their quadrature components of suitably selected internal modes satisfy the inseparability criterion. Clear physical insights for the origin of entanglement are given, and the required homodyne local oscillator pulse shape for optimum entanglement detection is determined.

Generation of squeezed pulses with a Sagnac loop fiber interferometer using a non-soliton femtosecond laser pulse at 800 nm

We experimentally demonstrate generation of a squeezed vacuum at 800 nm with a Sagnac loop fiber interferometer. When negative dispersion is properly added to an input laser pulse to compensate for the fiber dispersion, the level of squeezing is improved. A squeezed vacuum of 0.45 dB is obtained at a dispersion of -0.0157 ps(2) for the 1.5 m-long fiber loop. Since the squeezed vacuum is degraded by guided acoustic-wave Brillouin scattering (GAWBS), the noise level of the squeezing is improved by -0.3 dB at a liquid nitrogen temperature. We also demonstrate generation of photon number squeezing at -1.3 dB.

Quadrature measurements of a bright squeezed state via sideband swapping

The measurement of an arbitrary quadrature of a bright quantum state of light is a commonly requested action in many quantum information protocols, but it is experimentally challenging with previously proposed schemes. We suggest that the quadrature be measured at a specific sideband frequency of a bright quantum state by transferring the sideband modes under interrogation to a vacuum state and subsequently measuring the quadrature via homodyne detection. The scheme is implemented experimentally, and it is successfully tested with a bright squeezed state of light.

Observation of squeezed light at 1.535 microm using a pulsed homodyne detector

Squeezed light was generated at a telecommunication wavelength via single-pass optical parametric amplification in a periodically poled MgO-doped LiNbO(3) waveguide. Classical parametric deamplification of -8.9 dB was achieved. This large magnitude of deamplification indicates that the problem of gain-induced diffraction was avoided by employing the waveguide. Squeezing of 3.2 dB was directly observed using a time-domain pulsed homodyne detector.

Direct generation of a 10 GHz 816 fs pulse train from an erbium-fiber soliton laser with asynchronous phase modulation

By employing the technique of asynchronous mode locking, we have successfully demonstrated direct generation of stable 10 GHz 816 fs pulse trains with a supermode-suppression ratio >70 dB from a hybrid mode-locked Er-fiber laser. When the modulation frequency deviates from the cavity harmonic frequency by 15-40 kHz, stable femtosecond soliton pulses are formed. Our results demonstrate that asynchronous mode locking can act as an effective mechanism for achieving a shorter pulse width and for stabilizing high-repetition-rate pulse trains in soliton fiber lasers.

Generation of entanglement between frequency bands by nonlinear fiber propagation and spectral pulse shaping

A novel fiber-based scheme for generating quadrature entanglement between a specific pair of frequency bands is proposed. The scheme is based on use of a nonlinear fiber, a spectral pulse shaper, and an adaptive feedback loop. It is numerically predicted that at least -5 dB of the quadrature entanglement will be created by preparation of an appropriate initial phase spectrum. Optimal control of the four-wave mixing terms of the Kerr Hamiltonian is crucial for improvement of the entanglement.