Temperature-Tunable Telecom Photon-Pairs via Cascaded χ(2) Process in PPLN Waveguide

Samantaray, Ashish (2023) Temperature-Tunable Telecom Photon-Pairs via Cascaded χ(2) Process in PPLN Waveguide. Masters thesis, Indian Institute of Science Education And Research Kolkata.

Text (MS dissertation of Ashish Samantaray (18MS004)) Thesis_18MS004.pdf - Submitted Version Restricted to Repository staff only Download (2MB)

Abstract

We explore the cascaded second-order (χ(2)) nonlinear process of second-harmonic generation (SHG) + spontaneous parametric down-conversion (SPDC) in a type-0 phase-matched Zn-diffused MgO-doped periodically poled lithium niobate (PPLN) ridge waveguide at telecom wavelength. We simulate the waveguide using the finite element method (FEM) to determine the signal and idler peak wavelengths produced at a particular temperature and pump wavelength. In addition, we provide a detailed derivation of the effective χ(3) conversion efficiency (equivalent to the signal/idler photon flux). The cascaded χ(2) process produces temperature-tunable discrete sidebands (around a ∼1550-nm pump) that can be continuously tuned across the E-, S-, and U-bands of the telecom spectrum. Analysis of the joint spectral intensity (JSI) reveals the spectral correlation of the sidebands with a high entropy of entanglement (S), which is resistant to changes in the pump bandwidth and temperature. We also discuss the experimental setup to observe the stimulated cascaded χ(2) effect. Such frequency-correlated photon pairs with a high degree of frequency entanglement produced in a fiber-coupled integrated setup could have applications in quantum computing and communication.

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