Ferroelectric Physics and Domain Engineering
 
QPM Nonlinear Optics  and All-Solid-Laser
 
Polaritons in Dielectric Superlattice
 
Entangled Photons and Optical Superlattice
 
Plasmonics and Metamaterial




Entangled photons and optical superlattice
    

   Entangled photons generated by nonlinear optical interaction can be used to study the very fundamental issues in quantum mechanics such as nonlocality etc.. And entangled photons also play the key role in quantum computation and quantum communications. Therefore the new generation nonlinear optical material must greatly affect the development of quantum optics. As a type of newly developed nonlinear optical material, the optical superlattice has attracted great interest of researchers in quantum optics. It has been 20 years since our research group began the research on the optical superlattice. We can fabricate kinds of optical superlattice with unique optical properties which ensures colorful phase-matching conditions and abundant nonlinear optical coupling processes. All these advantages in nonlinear optics can be taken in the quantum optics. In recent several years, we began to study the nonclassical optical properties in this material including the entangled photons, continuous variable entanglement and so on. The main research area concludes the following issues.

New type of entangled two-photon, entangled three-photon and multi-photon state


Background:
   
The nonlinearity can be modulated both longitudinally and transversely in optical superlattice. It is equivalent that a nonlinear grating is written into the nonlinear crystal. The will definitely reforms the mode function of entangled photons. According to this basic principle, our research mainly focus on how to control and transform the entangled properties by the ferroelectric domain engineering technique, how to develop the new high-dimension entangled state and how these new state will be applied in quantum computation and quantum communication. In addition, we also theoretically studied the three-photon and multi-photon state generated from the optical superlattice including multi-photon interference, multi-photon lithography and multi-photon imaging.

Results:
    We successfully controlled the entangled photon’s wave front by domain engineering technique and nonlinear
Huygens-Fresnel principle. By a multi-channel periodically poled lithium tantalate, a high-dimensional entangled state was generated. The structure information of this superlattice was successfully transferred to the spatial properties of the entangled photons. A so-called subwavelength interference effect was experimentally verified. The results offer a new way to generate the entangled photons and can be applied in the quantum information. In the following figure, (a) is the coincidence counting rate when only one single photon detector scans, (b) is the coincidence counting rate when two detectors scan in-step and (c) is the diffraction pattern when the pump laser incident on the mask template of the multi-channel structure. The inset is the micrograph of the multi-channel periodically poled lithium tantalate.

  

 

New type of continuous variable entanglement


Background:
    The phase-matching is very flexible inside the optical superlattice and this can be used to generate the continuous variable entanglement with a unique color, two different colors and even multiple colors. The multi-component continuous variables entanglement can be used for new type of quantum dense coding and quantum communication. 

Results 1:
   
We theoretically studied the three-mode continuous variable entanglement which was generated from a quasi-periodic optical superlattice. This multi-component continuous variables entanglement actually contains 3 primary colors of the red, green and blue. This must have new applications in quantum communication. The left part in the following figure displays the structure of this sample and the right part is the RGB light generated from this sample.


 

ReferenceY. B. Yu, Z. D. Xie, X. Q. Yu, H. X. Li, P. Xu, H. M. Yao, and S. N. Zhu, Phys Rev. A 74, 042332 (2006).

Results 2:
    We theoretically studied the multi-pair continuous variables entanglement generated through the enhanced Raman process inside the optical superlattice. A frequency-comb continuous variable entanglement with tunable frequency interval was successfully generated. This can be used to develop a quantum WDM. The following is the quantum correlation between the stokes and anti-stokes Raman fields of the same order. The inset is the hexagonally pole lithium tantalate which generated the multi-order Raman scattering spectrum.

ReferenceY. B. Yu, S. N. Zhu, X. Q. Yu, P. Xu, J. F. Wang, Z. D. Xie, and H. Y. Leng, Phys. Rev. A 77, 032317 (2008)

 

In addition, we are on the pilot study of the cold molecules by laser controlling and its coherence characters.