Areas of Research
The team at The University of Glasgow research Shortwave Infrared (SWIR) Quantum Optics and Terahertz Photonics looking at quantum optics communication in SWIR domain to enable daylight quantum communication; study of matter mediated interaction between terahertz fields and quantum light.
As well as his interest in quantum optics, Dr. Adetunmise Dada also works in quantum measurements and metrology, designing and developing measurement schemes for quantum states of light and their application to novel quantum metrology tasks.
Experimental setup for generation and full tomography of polarization entangled photons at 2.1μm. The setup consists of mirrors (M1/2), an energy controller (EC), lenses (L1 and FC1/2), the periodically poled lithium niobate (PPLN) crystal (C), Ge filter (F0), a D-shaped pickoff mirror (D), 50-nm-passband filters (F1/2), halfwave plates (H1/2), quarterwave plates (Q1/2), polarizers (P1/2), single-mode fibers (SMF1/2), and superconducting nanowire single-photon detectors (SNSPD1/2).
The Use of Covesion PPLN Technology
The 2- to 2.5-μm spectral region is an optical telecommunications band of interest as it has a number of advantages over the traditional telecom C-band (1550 nm), making it crucial to research and develop quantum sources and measurement capabilities in this waveband.
The team at Glasgow, led by Dr Matteo Clerici, initially used PPLN crystals in 2019 when they demonstrated the first generation and characterization of indistinguishable photon pairs and polarization entanglement at 2.1 μm [1]. Degenerate photon pairs are produced via spontaneous parametric down-conversion (SPDC) in a second-order nonlinear crystal. They used a 1-mm-long periodically poled, magnesium-doped lithium niobate crystal (MgO-PPLN) from Covesion. The crystal length was chosen to guarantee maximum conversion efficiency and minimal temporal separation between the pump pulse and the generated SPDC field. The crystal had been poled with the ferroelectric domains periodically inverted to assure coherence between the pump field and the generated photonpair phase via quasi-phase matching for the whole length of the crystal and over a broad bandwidth. Different poling periods were tested to determine the optimal condition, and the experiments reported were obtained using a poling period of 30.8 μm and a stable temperature of (30 ± 0.1)°C.
In 2021, Dr. Dada led the team that generated photon pairs achieving near-maximal entanglement via spontaneous parametric down-conversion (SPDC) in a second-order nonlinear crystal with a configuration similar to that of their previous work [2]. For this research they used Covesion’s PPLN crystal with lengths 1 and 0.3 mm cut for type-0 and type-2 phase matching, respectively. The crystals were fabricated with different poling periods that were tested at different temperatures to determine the configuration that maximizes the signal and idler photon count rates in each case.
Why Covesion?
"We had become aware of Covesion’s products while working in the Extreme Light Group and Quantum Photonics Laboratory at Heriot-Watt University in Edinburgh.
The customer service from Covesion has always been excellent. We have a great rapport with Corin (Professor Corin Gawith, CTO, Covesion) and the team, and their knowledge is invaluable. I have had occasion to use Covesion crystals twice during my research at The University of Glasgow and the turnaround for the custom products was very quick, meaning the research could continue without delay.
Specifically with regards to our area of interest, the PPLN crystals are periodically poled, and the period of poling needs to be optimised to ensure the best performance of the source, enhancing the efficiency of the generation. Covesion gave us various options rather than just one specific period for the poling. For example, in one of the devices there were different groups of poling periods and that allowed us to optimise for best performance and find the configuration that worked the best."
Dr. Adetunmise Dada, Lecturer in Optics, School of Physics and Astronomy, University of Glasgow
References
- https://www.science.org/doi/10.1126/sciadv.aay5195
- https://journals.aps.org/prapplied/abstract/10.1103/PhysRevApplied.16.L051005
