Abstract-Invited Article: Ultra-broadband terahertz coherent detection via a silicon nitride-based deep sub-wavelength metallic slit

APL Photonics

A. Tomasino, R. Piccoli, Y. Jestin, S. Delprat1, M. Chaker,   M. Peccianti,   M. Clerici4, A. Busacca, L. Razzari,  R. Morandotti,

FIG. 1.3D sketch of the deep sub-λ slit (G) device embedded in a thin layer (T) of SiN, deposited on a quartz substrate. L and W are the length and the width of the metal pads, respectively.

https://aip.scitation.org/doi/abs/10.1063/1.5052628

We present a novel class of CMOS-compatible devices aimed to perform the solid-state-biased coherent detection of ultrashort terahertz pulses, i.e., featuring a gap-free bandwidth at least two decades-wide. Such a structure relies on a 1-µm-wide slit aperture located between two parallel aluminum pads, embedded in a 1-µm-thick layer of silicon nitride, and deposited on a quartz substrate. We show that this device can detect ultra-broadband terahertz pulses by employing unprecedented low optical probe energies of only a few tens of nanojoules. This is due to the more than one order of magnitude higher nonlinear coefficient of silicon nitride with respect to silica, the nonlinear material employed in the previous generations. In addition, due to the reduced distance between the aluminum pads, very high static electric fields can be generated within the slit by applying extremely low external bias voltages (in the order of few tens of volts), which strongly enhance the dynamic range of the detected THz waveforms. These results pave the way to the integration of solid-state ultra-broadband detection in compact and miniaturized terahertz systems fed by high repetition-rate laser oscillators and low-noise, low-voltage generators.

Abstract-High resolution continuous wave terahertz spectroscopy on solid-state samples with coherent detection

De-Yin Kong, Xiao-Jun Wu, Bo Wang, Yang Gao, Jun Dai, Li Wang, Cun-Jun Ruan, and Jun-Gang Miao

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-26-14-17964

We systematically investigate the data analysis methods in terahertz frequency domain spectroscopy (THz-FDS) with coherent detection. We demonstrate that the Hilbert transform method is one of the most appropriate for data processing in THz-FDS. By converting frequency-domain signal into time domain with further data processing, the system noise due to Fabry–Pérot (FP) interference is greatly restrained. Accurate permittivity of lactose monohydrate is successfully extracted under the condition of the existence of atmospheric water vapor. Our work greatly promotes the development of THz spectroscopy in practical applications.

© 2018 Optical Society of America

Abstract-Coherent detection of THz-induced sideband emission from excitons in the nonperturbative regime

K. Uchida, T. Otobe, T. Mochizuki, C. Kim, M. Yoshita, K. Tanaka, H. Akiyama, L. N. Pfeiffer, K. W. West, and H. Hirori

https://journals.aps.org/prb/accepted/43076O14Z2210330d36f6038100d0aa224fae6d98

Strong interaction of terahertz (THz) waves with excitons induces nonperturtbative optical effects such as Rabi splitting and high-order sideband generation. Here, we investigated coherent properties of THz-induced sideband emissions from GaAs/AlGaAs multi-quantum-wells, and determined the optical susceptibility of the THz dressed exciton in the nonperturbative regime. The strong dependences of both amplitude and phase of the second-order sideband emission on the THz electric field strength imply that the field ionization of the 1s exciton modifies the THz-dressed exciton's energy spectrum.

Abstract-Silicon-plasmonic integrated circuits for terahertz signal generation and coherent detection

Tobias Harter, Sascha Muehlbrandt, Sandeep Ummethala, Alexander Schmid, Lothar Hahn, Wolfgang Freude, Christian Koos

https://arxiv.org/abs/1802.08506

Optoelectronic signal processing offers great potential for generation and detection of ultra-broadband waveforms in the THz range, so-called T-waves. However, fabrication of the underlying high-speed photodiodes and photoconductors still relies on complex processes using dedicated III-V semiconductor substrates. This severely limits the application potential of current T-wave transmitters and receivers, in particular when it comes to highly integrated systems that combine photonic signal processing with optoelectronic conversion to THz frequencies. In this paper, we demonstrate that these limitations can be overcome by plasmonic internal photoemission detectors (PIPED). PIPED can be realized on the silicon photonic platform and hence allow to leverage the enormous opportunities of the associated device portfolio. In our experiments, we demonstrate both T-wave signal generation and coherent detection at frequencies of up to 1 THz. To proof the viability of our concept, we monolithically integrate a PIPED transmitter and a PIPED receiver on a common silicon photonic chip and use them for measuring the complex transfer impedance of an integrated T-wave device.

Abstract-Coherent detection of THz laser signals in optical fiber systems

Thomas G. Folland, Owen P. Marshall, Harvey E. Beere, David A. Ritchie, and Subhasish Chakraborty


https://www.osapublishing.org/oe/abstract.cfm?uri=oe-25-21-25566&origin=search

Terahertz (THz) coherent detectors are crucial for the stabilization and measurement of the properties of quantum cascade lasers (QCLs). This paper describes the exploitation of intra-cavity sum frequency generation to up-convert the emission of a THz QCL to the near infrared for detection with fiber optic coupled components alone. Specifically, a low cost infrared photodiode is used to detect a radio frequency (RF) signal with a signal-to-noise ratio of approximately 20dB, generated by beating the up-converted THz wave and a near infrared local oscillator. This RF beat note allows direct analysis of the THz QCL emission in time and frequency domains. The application of this technique for QCL characterization is demonstrated by analyzing the continuous tuning of the RF signal over 2 GHz, which arises from mode tuning across the QCL’s operational current range.

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 detection for continuous terahertz wave

Hui Yuan, Tielin Lu, Jingshui Zhang, Yuejin Zhao

Beijing Institute of Technology (China)

Liangliang Zhang, Ji Zhao

Capital Normal Univ. (China)

Proc. SPIE 9585, Terahertz Emitters, Receivers, and Applications VI, 95850O (August 31, 2015); doi:10.1117/12.2187465

http://proceedings.spiedigitallibrary.org/proceeding.aspx?articleid=2434792

In this paper we demonstrated a coherent raster-scan imaging system that can acquire phase information based on continuous terahertz imaging. It mixes the terahertz with a Fs-laser by a electro-optic crystal of ZnTe to make a hybrid modulation on the crystal to achieve continuous terahertz detection. In this way, it can not only propagate for a long distance but also achieve phase detection for continuous terahertz imaging. The surface images of objects that are under test can be obtained by the Backward-Wave Oscillator, which the output power is 10mW at 205.994GHz. With the repetition frequency of 80MHz, the output power of the MaiTai is 1.65W and 100fs pulse light at 800nm. The images can achieve diffraction-limited resolution approximately. And the simulated results show that the system can obtain phase imaging of test objects based on continuous terahertz source. The way to get the phase of the signal has significant meaning for coherent detection of continuous terahertz source.
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