Squeezing from Lasers

Sitotaw Eshete

The squeezing and statistical properties of a pair of superposed non-degenerate three-level lasers coupled to a squeezed vacuum reservoir could be analyzed with the help of the density operator for a pair of superposed twomode laser light.We have determined the quadrature variances of the cavity modes.The results show that the light produced by the system under consideration is in squeezed state.According to our work, the quadrature squeezing for a pair of superposed laser light beams is found to be the average of the quadrature squeezing of the separate lasers.The presence of squeezed vacuum reservoir enhances the quadrature squeezing significantly.

David F. P. Pile

Andrew G. White, Timothy C. Ralph, Hans‐A. Bachor

The characteristics of squeezed light generated by both passive (occurring in a cavity external to a laser) and active (occurring within a laser cavity) second-harmonic generation (SHG) are investigated and contrasted. Squeezing of both the fundamental and the second harmonic is discussed, and the issue of doubly versus singly resonant behavior is addressed. We examine passive squeezing by explicitly modeling the intrinsically noisy output of the pump laser and coupling it to a passive, multiport, lossy SHG cavity. Low-frequency degradation of the squeezing caused by the laser pump noise is predicted and provides a probable explanation for previous discrepancies between theory and experiment. Active squeezing is quantitatively modeled by a three-level laser model that retains all laser dynamics. Previously disparate predictions are reconciled. For one parameter set two regimes of squeezing are predicted: 50% squeezing at frequencies lower than the laser relaxation oscillation, and near-perfect squeezing at frequencies above. A particular problem of active squeezing is highlighted: The fast dephasing of the laser coherence introduces considerable excess noise likely to mask squeezing in experimental situations. We conclude that, although passive SHG is a practical source of squeezing, active SHG is unlikely to be so in the foreseeable future.

Harry Paul

Daniele Nello, Giuseppe Patera, Lorenzo Columbo

We present a comprehensive study of quadrature squeezing in a quantum well laser based on a fully quantum Langevin approach. We compute the frequency-resolved squeezing map of the laser field and identify optimal squeezing curves, revealing, for the first time to our knowledge, both frequency-dependent squeezing and complex or hidden squeezing in a semiconductor laser. We further analyse the role of the linewidth enhancement factor (alpha-factor) in the emergence of these features. Our results establish semiconductor lasers as a platform for the generation of non-classical light and open new perspectives for their application in quantum communication and sensing.

Richart E. Slusher, Bernard Yurke