Investigation of non-classical light and its application in ultrasensitive measurements

Recent advances in quantum optics and quantum information science have opened the possibility of entirely new methods for forming optical images with unprecedented sensitivity and resolution. This new field of research, known as quantum imaging, has led to other breakthroughs as well, such as the possibility of making spatial measurements of displacement and tilt of a laser beam below the quantum noise limit. In addition, quantum imaging offers significant opportunities within the fields of quantum communication and quantum information processing as it allows a secure two-dimensional information transfer and teleportation. Understanding the spatial aspects of quantum fluctuations and quantum correlations provides a great potential for further technological applications within this field. For investigating the basics of the spatial quantum effects, we require a multimode squeezed light, where the light beam displays nonclassical spatial properties in the transverse direction. Such a source of squeezed spatial light can be based on optical parametric amplifiers, widely used in quantum optics experiments for generating amplitude or phase squeezed light. The first attempt for achieving the goal is to generate squeezing in the higher-order Hermite-Gauss modes, in particular in the TEM10 spatial mode, which form an optimum basis for measurements of displacement and tilt of a laser beam. This requires understanding of mode coupling between the different transverse modes in a nonlinear device; in our case via the second-order nonlinear interaction. In our work we have studied the second-order nonlinear interaction between the higher-order Hermite-Gauss modes via second harmonic generation in a PPKTP nonlinear medium, and applied these results in reverse to generate a squeezed light in the TEM10 higher-order spatial mode utilizing an optical parametric amplifier. Our primarily objective was to design an efficient squeezing source operating in this particular spatial mode. We generated vacuum squeezed light and observed a noise suppression of -2.9 dB below the quantum noise limit. We studied further optimization of the nonlinear gain of the amplifier in order to achieve higher degrees of squeezing in the TEM10 mode. This in effect promises higher sensitivity for measurements of displacement and tilt of a laser beam below the quantum noise limit. We have experimentally demonstrated the generation of optical squeezing in multiple longitudinal modes and transverse Hermite-Gauss modes of an optical parametric amplifier. We present measurements of approximately -3 dB squeezing at baseband, 1.7 GHz, 3.4 GHz and 5.1 GHz, which correspond to the first, second and third resonances of the amplifier. We show that both the magnitude and the bandwidth of the squeezing in the higher longitudinal modes are greater than can be observed at baseband. The squeezing observed is the highest frequency squeezing reported to date. In addition to squeezed light, the so-called entangled beams or EPR-beams are of great interest. Entangled beams give us the opportunity to investigate fundamental quantum properties of twin light beams, such as non-locality and entanglement. These quantum properties are presently seen as fundamental to future technological