Session C3: Optics I

Light, the Nexus in Phyiscs

The United Nations declared 2015 to be "The International Year of Light and Light-Based Technologies." In a concept map of physics, the study of light stands at all the major intersections. Just as scattered light rays illuminate the whole house, insights into light have illuminated the whole of physics.. In 1267 Roger Bacon wrote of optics, "no other science has so much sweetness and beauty and utility. Therefore it is the flower of the whole of philosophy and through it, and not without it, can other sciences be known." We typically think of optics as a study of light, but here we imagine the whole of physics as the study of light. This talk will not be a formal history, but a celebration of connections in physics that are made by light.   

Parametric generation of high frequency coherent light in negative index materials and materials with strong anomalous dispersion

We demonstrate the possibility of generation of coherent radiation with tunable frequencies higher than the frequency of the driving field $\nu _{d}$ in a nonlinear medium utilizing the difference combination resonance that occurs when $\nu _{d}$ matches the difference of the frequencies of the two generated fields $\omega _{1}$ and $\omega _{2}$. We find that such a resonance can appear in materials which have opposite signs of refractive index at $\omega _{1}$ and $\omega _{2}$. It can also occur in positive refractive index materials with strong anomalous dispersion if at one of the generated frequencies the group and phase velocities are opposite to each other. We show that the light amplification mechanism is equivalent to a combination resonance in a system of two coupled parametric oscillators with the opposite sign of masses. Such a mechanism holds promise for a new kind of light source that emits coherent radiation of tunable wavelengths by an optical parametric amplification process with the frequency higher than $\nu_{d}$.   

Topological charge algebra of optical vortices in nonlinear interactions

We investigate the transfer of orbital angular momentum among multiple beams involved in a coherent Raman interaction. We use a liquid crystal light modulator to shape the pump beam into an optical vortex with various integer values of topological charge. We then cross the pump beam with an unshaped Stokes beam in a Raman-active crystal to produce multiple Stokes and anti-Stokes sidebands. By using a tilted-lens technique and measuring the resultant vortex charges, we verify that the generated beams’ topological charges obey a simple equation. This equation can be derived from angular momentum conservation for created and annihilated photons, or alternatively, from phase-matching considerations for the multiple interacting beams.   

Non-perturbative approach to three-pulse photon echo

We rewrite the nonlinear spectroscopy response with the formalism developed in quantum optics. Instead of commonly used perturbation approach, we adapt a quantum dynamical evolution into the calculation of signal. In this new approach, we show that high-order terms has essential contribution to the nonlinear signal of the three-pulse photon echo. A detailed study of the two-pulse and three-pulse echo is performed to show the advantage of using three pulses in the experiments to direct probe the coherence between two excited states. We demonstrate the principal with a three-level V-type system. And we show the correlation between the bath modes of the two excited states may induce a longer decoherence time than that with only independent baths.   

Entangling two coherent light beams through stimulated emission

Stimulated emission plays the central role in generating laser, and it can also be used to entangle two coherent light beams in a two-level atomic ensemble. When the pumping rate of the atomic system is smaller than its decay rate, the atomic ensemble can be consider as a device of photon subtraction. On the other hand, if the pumping rate of the atomic system is substantially lager than the decay rate, the atomic ensemble plays the role of photon addition, which can be used to entangle two coherent light beams. This is a novel way to generate bright entangled lights, even without using any nonlinear material.   

Delayed-Choice Quantum Eraser Using Thermal Light

In a Young's double-slit interferometer, the common understanding is that the position-momentum uncertainty relation makes it impossible to determine which slit a photon or wavepacket passes through without at the same time disturbing the photon or wavepacket enough to destroy the interference pattern. It has been shown that this common understanding may not be true. In 1982, Scully and Druhl showed that a \quantum eraser" may erase the which-path information even after the annihilation of the quantum itself and determine its early wave-like or particle-like behavior. We discuss two experimental realizations of delayed choice quantum eraser in this talk. One experiment was demonstrated in 2000 based on the coincidence measurement or the photon-number correlation measurement of entangled photon pairs. Another recent demonstration has a similar experimental setup, however, the coincidence measurement is on the photon-number fluctuation correlation of randomly paired photons of thermal light.