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The term photonic crystals appears because of the analogy between electron waves in crystals and the light waves in artificial periodic dielectric structures. During the recent years the investigation of one-, two-and three-dimensional periodic structures has attracted a widespread attention of the world optics community because of great potentiality of such structures in advanced applied optical fields. The interest in periodic structures has been stimulated by the fast development of semiconductor technology that now allows the fabrication of artificial structures, whose period is comparable with the wavelength of light in the visible and infrared ranges.

http://ieeexplore.ieee.org/iel5/6354/16969/00781867.pdf

Photonic crystals

(b) Write out the equations for the time dependence of ρ11, ρ22, ρ12 and ρ21 assuming that a light field interaction V = -μ12Ee iωt + c.c. couples only levels |1> and |2>, and that the excited levels exhibit spontaneous decay. (8 marks) (c) Under steady-state conditions, find the ratio of populations in states |2> and |3>. (3 marks) (d) Find the slowly varying amplitude ̃ ρ 12 of the polarization ρ12 = ̃ ρ 12e iωt . (6 marks) (e) In the limiting case that no decay is possible from intermediate level |3>, what is the ground state population ρ11(∞)? (2 marks) 2. (15 marks total) In a 2-level atom system subjected to a strong field, dressed states are created in the form |D1(n)> = sin θ |1,n> + cos θ |2,n-1> |D2(n)> = cos θ |1,n> sin θ |2,n-1>

The Quantum Theory of Light

Squeezed states of the electromagnetic field have been generated by nondegenerate four-wave mixing due to Na atoms in an optical cavity. The optical noise in the cavity, comprised of primarily vacuum fluctuations and a small component of spontaneous emission from the pumped Na atoms, is amplified in one quadrature of the optical field and deamplified in the other quadrature. These quadrature components are measured with a balanced homodyne detector. The total noise level in the deamplified quadrature drops below the vacuum noise level.

Observation of squeezed states generated by four-wave mixing in an optical cavity

Wave propagation and group velocity

Spontaneous emission in photonic crystals with anisotropic three-dimensional dispersion relation is studied. If the upper level is below a characteristic frequency ${\ensuremath{\omega}}_{1}$, or above ${\ensuremath{\omega}}_{2}$, or between ${\ensuremath{\omega}}_{1}$ and ${\ensuremath{\omega}}_{2}$, the radiation is a localized field with a frequency in the band gap, or a propagating field with a frquency in the band, or a diffusion field, respectively. An analytical expression for the Lamb shift is obtained. The Lamb shift for the current case is small compared to that in an ordinary vacuum or in one- or two-dimensional photonic crystals due to lower density of states.

Spontaneous radiation and lamb shift in three-dimensional photonic crystals

The quantum interference between two spontaneous emission transitions, which are orthogonal, in a three-level system, can be greatly enhanced by using left-handed materials due to the focusing and phase compensation effects. The influence of the dispersion and dissipation of the materials on the quantum interference enhancement is investigated, and the enhancement of quantum interference is still significant. The quantum interference enhancement will result in a large quenching of the spontaneous emission, even if the distance between the materials and systems is larger than 10 wavelengths.

Quantum interference enhancement with left-handed materials.

We investigate the generation of squeezed states in a movable mirror in dissipative optomechanics in which the oscillating mirror modulates both the resonance frequency and the linewidth of the cavity mode. Via feeding broadband squeezed-vacuum light accompanying a coherent driving laser field into the cavity, the master equation for the cavity-mirror system is derived by following the general reservoir theory. When the mirror is weakly coupled to the cavity mode, we find that the driven cavity field can effectively perform as a squeezed-vacuum reservoir for the movable mirror via utilizing the completely destructive interference of quantum noise. Efficient transfer of squeezing from the light to the movable mirror occurs, irrespective of the ratio between the cavity damping rate and the mechanical frequency. Moreover, when the mirror is moderately coupled to the cavity mode, photonic excitation can preclude the completely destructive interference of quantum noise. As a consequence, the mirror deviates from the ideal squeezed state.

Generation of squeezed states in a movable mirror via dissipative optomechanical coupling

Optical nonreciprocity is important in photonic information processing to route the optical signal or prevent the reverse flow of noise. By adopting the strong nonlinearity associated with a few atoms in a strongly coupled cavity QED system and an asymmetric cavity configuration, we experimentally demonstrate the nonreciprocal transmission between two counterpropagating light fields with extremely low power. The transmission of 18% is achieved for the forward light field, and the maximum blocking ratio for the reverse light is 30 dB. Though the transmission of the forward light can be maximized by optimizing the impedance matching of the cavity, it is ultimately limited by the inherent loss of the scheme. This nonreciprocity can even occur on a few-photon level due to the high optical nonlinearity of the system. The working power can be flexibly tuned by changing the effective number of atoms strongly coupled to the cavity. The idea and result can be applied to optical chips as optical diodes by using fiber-based cavity QED systems. Our work opens up new perspectives for realizing optical nonreciprocity on a few-photon level based on the nonlinearities of atoms strongly coupled to an optical cavity.

Realization of Nonlinear Optical Nonreciprocity on a Few-Photon Level Based on Atoms Strongly Coupled to an Asymmetric Cavity.

Electromagnetically induced transparency (EIT) in metamaterials is studied experimentally in a waveguide system with tunable intrinsic loss. There is a window in the transmission spectrum with nearly unchanged maximum transmittance, which is the result of simultaneous suppression of reflection and absorption. Group delay measurements demonstrate the transmission-delay product is almost independent of the intrinsic loss while the bandwidth-delay product is affected. Dynamic evolution of EIT in metamaterials is also investigated and we observe parameter-controllable excitation transfer from the bright resonator to the dark resonator during the process of EIT buildup.

Yaping Yang

Papers

Spontaneous radiation and lamb shift in three-dimensional photonic crystals

Quantum interference enhancement with left-handed materials.

Generation of squeezed states in a movable mirror via dissipative optomechanical coupling

Realization of Nonlinear Optical Nonreciprocity on a Few-Photon Level Based on Atoms Strongly Coupled to an Asymmetric Cavity.

Electromagnetically induced transparency in metamaterials: Influence of intrinsic loss and dynamic evolution