Year: 2017
Type: dissertation
Abstract: Spectrally unentangled biphotons with high single-spatiotemporal-mode purity are highly desirable for many quantum information processing tasks.We generate biphotons with an inferred heralded-state spectral purity of 99%, the highest to date without any spectral filtering, by pulsed spontaneous parametric down-conversion (SPDC) in a custom-fabricated periodically-poled KTiOPO 4 (PPKTP) crystal under extended Gaussian phase-matching conditions.The high purity achieved is made possible by the Gaussian phase-matching function of our custom PPKTP crystal.Without applying spectral filtering and using a standard PPKTP crystal, the highest previously reported purity is 93%.We characterize the joint spectral density of the generated biphoton by converting the spectral content to temporal information via dispersion through a 42-km SMF28 fiber.To characterize the JSD at high spectral resolution and more efficiently, we employ a commercially available dispersion compensation module (DCM) with a dispersion equivalent to 100 km of standard optical fiber and with an insertion loss of only 2.8 dB.Compared with the typical method of using two temperature-stabilized equal-length fibers that incurs an insertion loss of 20 dB per fiber, the DCM approach achieves high spectral resolution in a much shorter measurement time.We also verify the indistinguishability of the SPDC signal and idler photons via Hong-Ou-Mandel interferometric measurements.The near perfect interference visibility confirms that they are indeed indistinguishable.
Author: Changchen Chen
Language: English
Subfield: Atomic and Molecular Physics, and Optics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2767005430