Synchrotron terahertz absorption measurements and polariton gain modelling of 5 mol% MgO:LiNbO₃ at cryogenic temperatures

Authors

Ameera A. Jose ⋅ AU MQ Photonics Research Centre, Department of Physics and Astronomy, Macquarie University
Ondrej Kitzler ⋅ AU MQ Photonics Research Centre, School of Mathematical and Physical Sciences, Macquarie University
Helen M. Pask ⋅ AU MQ Photonics Research Centre, School of Mathematical and Physical Sciences, Macquarie University
David J. Spence ⋅ AU MQ Photonics Research Centre, School of Mathematical and Physical Sciences, Macquarie University

Abstract

We determined the absorption coefficient of 5 mol% MgO:LiNbO₃ using synchrotron measurements of the crystal's transmission and reflection over the frequency range from 0.75 – 6 THz and temperatures 37 K to 300 K. The spectra cover almost the entire low-frequency branch of the 252 cm⁻¹ (7.4 THz) A₁ polariton mode, which is commonly utilized in terahertz lasers based on stimulated polariton scattering. A broad peak at 3.15 THz was observed, which we assigned to be a low-frequency defect mode that causes increased polariton damping. We used Gaussian gain theory to estimate the Stokes gain at 77 K and 300 K. The additional mode strongly affects the gain which explains the difficulty of MLN's THz generation beyond 3 THz. Our model also predicts possible tuning around the 4 THz region, which could further be improved by crystal cooling.

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Issue

2022: Proceedings of the 40th Samahang Pisika ng Pilipinas Physics Conference

Article ID

SPP-2022-1F-03

Section

Optics and Photonics

Published

2022-09-29

How to Cite

[1]

AA Jose, O Kitzler, HM Pask, and DJ Spence, Synchrotron terahertz absorption measurements and polariton gain modelling of 5 mol% MgO:LiNbO3 at cryogenic temperatures, Proceedings of the Samahang Pisika ng Pilipinas 40, SPP-2022-1F-03 (2022). URL: https://proceedings.spp-online.org/article/view/SPP-2022-1F-03.