Abstract-Ultra-high-resolution software-defined photonic terahertz spectroscopy

 

Rodolfo I. Hermans, James Seddon, Haymen Shams, Lalitha Ponnampalam, Alwyn J. Seeds, and Gabriel Aeppli

Experiment schematic: a monochromatic telecommunications wavelength laser feeds an optical frequency comb generator (OFCG) with exact tunable spacing. A programmable wavelength selective switch (WSS) selects two bands 12 peaks apart, amplified and mixed in uni-traveling-carrier photo-diode (UTC-PD). A 200 GHz beat frequency is transmitted through horn antennas and lenses through a continuous-flow liquid helium cryostat with thin polypropylene windows and LiYF4:Ho3+${\mathrm{L}\mathrm{i}\mathrm{Y}\mathrm{F}}_4:{\mathrm{H}\mathrm{o}}^{3+}$ sample. The received signal is down-converted using a sub-harmonic mixer and measured using a microwave spectrum analyzer.

https://www.osapublishing.org/optica/abstract.cfm?uri=optica-7-10-1445

A novel technique for high-resolution 1.5µm$1.5\text{µ}\mathrm{m}$ photonics-enabled terahertz (THz) spectroscopy using software control of the illumination spectral line shape (SLS) is presented. The technique enhances the performance of a continuous-wave THz spectrometer to reveal previously inaccessible details of closely spaced spectral peaks. We demonstrate the technique by performing spectroscopy on LiYF4:Ho3+${\mathrm{L}\mathrm{i}\mathrm{Y}\mathrm{F}}_4:{\mathrm{H}\mathrm{o}}^{3+}$, a material of interest for quantum science and technology, where we discriminate between inhomogeneous Gaussian and homogeneous Lorentzian contributions to absorption lines near 0.2 THz. Ultra-high-resolution (<100Hz$<100\mathrm{H}\mathrm{z}$ full-width at half maximum) frequency-domain spectroscopy with quality factor 𝑄>2×109$Q>2\times {10}^9$ is achieved using an exact frequency spacing comb source in the optical communications band, with a custom uni-traveling-carrier photodiode mixer and coherent down-conversion detection. Software-defined time-domain modulation of one of the comb lines is demonstrated and used to resolve the sample SLS and to obtain a magnetic field-free readout of the electronuclear spectrum for the Ho3+${\mathrm{H}\mathrm{o}}^{3+}$ ions in LiYF4:Ho3+${\mathrm{L}\mathrm{i}\mathrm{Y}\mathrm{F}}_4:{\mathrm{H}\mathrm{o}}^{3+}$. In particular, homogeneous and inhomogeneous contributions to the spectrum are readily separated. The experiment reveals previously unmeasured information regarding the hyperfine structure of the first excited state in the 5𝐼8${}^5{I}_8$ manifold complementing the results reported in Phys. Rev. B 94, 205132 (2016) [CrossRef]  .

Published by The Optical Society under the terms of the Creative Commons Attribution 4.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

Abstract-Coherent terahertz photonics

 

 

 

Alwyn J. Seeds, Martyn J. Fice, Katarzyna Balakier, Michele Natrella, Oleg Mitrofanov, Marco Lamponi, Mourad Chtioui, Frederic van Dijk, Michael Pepper, Gabriel Aeppli, A. Giles Davies, Paul Dean, Edmund Linfield, and Cyril C. Renaud

http://www.opticsinfobase.org/oe/abstract.cfm?uri=oe-21-19-22988

We present a review of recent developments in THz coherent systems based on photonic local oscillators. We show that such techniques can enable the creation of highly coherent, thus highly sensitive, systems for frequencies ranging from 100 GHz to 5 THz, within an energy efficient integrated platform. We suggest that such systems could enable the THz spectrum to realize its full applications potential. To demonstrate how photonics-enabled THz systems can be realized, we review the performance of key components, show recent demonstrations of integrated platforms, and give examples of applications.

© 2013 OSA

Abstract-Polarization-independent dual-band terahertz metamaterial absorbers based on gold/parylene-C/silicide structure

Polarization-independent dual-band terahertz metamaterial absorbers based on gold/parylene-C/silicide structure Yongzheng Wen, Wei Ma, Joe Bailey, Guy Matmon, Xiaomei Yu, and Gabriel Aeppli  »View Author Affiliations http://www.opticsinfobase.org/ao/abstract.cfm?uri=ao-52-19-4536

We design, fabricate, and characterize dual-band terahertz (THz) metamaterial absorbers with high absorption based on structures consisting of a cobalt silicide (Co-Si) ground plane, a parylene-C dielectric spacer, and a metal top layer. By combining two periodic metal resonators that couple separately within a single unit cell, a polarization-independent absorber with two distinct absorption peaks was obtained. By varying the thickness of the dielectric layer, we obtain absorptivity of 0.76 at 0.76 THz and 0.97 at 2.30 THz, which indicates the Co-Si ground plane absorbers present good performance.

© 2013 Optical Society of America