Squeezed light

For a light source of a specific power, there is a fundamental limit to the precision to which the intensity can be determined within a specific period. This is termed the shot-noise limit. If n photons are accumulated, the variance is /n and the signal-to-noise ratio (S/N) is fnln. Any additional noise source (due to the amphfier, interference or detector imperfections) will degrade this value. Theoretically, shot-noise in coherently squeezed light can be slightly lower than this limit, but ultimately only by a factor of 1/ 2. 

Let us now turn to squeezed light. We define quadrature components of single and compound modes ... 

Because of the linearity of Heisenberg-Langevin equations, the squeezing does not depend on the initial complex amplitudes of optical modes. Squeezed light... 

Popp FA, Chang JJ, Herzog A, Yan Z, Yan Y. Evidence of non-classical (squeezed) light in biological systems. Phys Lett A 2002 293 98-102. 

Squeezing Light Near-field Scanning Optical Microscopy... 

Another example, where a beam of squeezed light was realized with 3.2 mW and 52 % noise reduction, is the second-harmonic generation with a cw Nd YAG laser in a monolithic resonator [1337]. The experimental setup is shown in Fig. 9.101a. 

Fig. 9.101 (a) Experimental setup for the generation of bright squeezed light by second-harmonic generation in a monolithic resonator (b) spectral power density of photocurrent fluctuations for squeezed light input to a balanced homodyne detector. The upper curve (/> gives the shot-noise level [1337]... 

In Sect. 9.8.1 it was shown that the noise limit without squeezing is caused by the zero-point field coupled into the second input part of the interferometer. If a beam of squeezed light is fed into this input part, the noise level can be decreased and the detectable length change AL can be further decreased [1356]. 

The combination of Ramsey spectroscopy (see Sect. 9.3) and squeezed light has brought an increased spectral resolution. While traditional Ramsey spectroscopy allows the resolution Am = 2nl2>T where T is the flight time of the molecules between the two separated fields, using two-mode squeezed light and two-atom excitation with joint detection a spectral resolution oin/3T could be achieved [1355]. 

P. Kurz, R. Paschotta, K. Fiedler, J. Mlynek, Bright squeezed light by second harmonic generation and monolytic resonator. Europhys. Lett. 24,449 (1993)... 

K. Qu, G.S. Agaral, Ramsey spectroscopy using squeezed light. Opt. Lett. 38,2563 (2013)... 

J. Bergou, C. Benkert, L. Davidovich and et al. Double two-photon correlated-spontaneous-emission lasers as bright sources of squeezed light. Physical Revew A 1990 Nov l 42(9) 5544-5552. 

Klaus M. Gheri, Daniel F. Walls. Lossless transformation of coherent light into amplitude-squeezed light. Physical Revew A 1992 Dec 1 46(11) R6793 - R6796. 

T. C. Ralph, C. M. Savage. Squeezed light from a coherently pumped four-level laser Physical Revew A 1991 Dec 1 44(11) 7809-7814. 

Appel J, Figueroa E, Korystov D et al. Quantum memory for squeezed light. Physical Review Letters 2008 Mar 5 100(9) 093602(4). 

Fluid coking—a process that uses a reactor to scrape the bottom of the barrel and squeeze light products out of the residue. 

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