Abstract-Wavelength conversion through plasmon-coupled surface states

 

Deniz Turan, Ping Keng Lu, Nezih T. Yardimci, Zhaoyu Liu, Liang Luo, Joong-Mok Park, Uttam Nandi, Jigang Wang, Sascha Preu, Mona Jarrahi

Wavelength conversion through plasmon-coupled surface states.

Built-in electric field profile and its impact on the wavelength conversion efficiency.

https://www.nature.com/articles/s41467-021-24957-1

Surface states generally degrade semiconductor device performance by raising the charge injection barrier height, introducing localized trap states, inducing surface leakage current, and altering the electric potential. We show that the giant built-in electric field created by the surface states can be harnessed to enable passive wavelength conversion without utilizing any nonlinear optical phenomena. Photo-excited surface plasmons are coupled to the surface states to generate an electron gas, which is routed to a nanoantenna array through the giant electric field created by the surface states. The induced current on the nanoantennas, which contains mixing product of different optical frequency components, generates radiation at the beat frequencies of the incident photons. We utilize the functionalities of plasmon-coupled surface states to demonstrate passive wavelength conversion of nanojoule optical pulses at a 1550 nm center wavelength to terahertz regime with efficiencies that exceed nonlinear optical methods by 4-orders of magnitude.

Abstract-An efficient Terahertz rectifier on the graphene/SiC materials platform

Maria T. Schlecht, Sascha Preu, Stefan Malzer,  Heiko B. Weber,

https://www.nature.com/articles/s41598-019-47606-6?utm_source=other_website&utm_medium=display&utm_content=leaderboard&utm_campaign=JRCN_2_LW_X-moldailyfeed

We present an efficient Schottky-diode detection scheme for Terahertz (THz) radiation, implemented on the material system epitaxial graphene on silicon carbide (SiC). It employs SiC as semiconductor and graphene as metal, with an epitaxially defined interface. For first prototypes, we report on broadband operation up to 580 GHz, limited only by the RC circuitry, with a responsivity of 1.1 A/W. Remarkably, the voltage dependence of the THz responsivity displays no deviations from DC responsivity, which encourages using this transparent device for exploring the high frequency limits of Schottky rectification in the optical regime. The performance of the detector is demonstrated by resolving sharp spectroscopic features of ethanol and acetone in a THz transmission experiment.

Abstract-Picosecond-scale Terahertz pulse characterization with field-effect transistors

Stefan Regensburger, Stephan Winnerl,  J. Michael Klopf,  Hong Lu, Arthur C. Gossard,  Sascha Preu

https://ieeexplore.ieee.org/document/8662700

Precise real-time detection of Terahertz pulses is a key requirement for characterization of pulsed Terahertz sources and non-destructive testing applications. We experimentally evaluate the speed limits of Terahertz rectification in field-effect transistors using the example of pulses from a free-electron laser. We develop an improved model for the description of these Terahertz pulses and demonstrate its validity experimentally by comparison to spectroscopic data as well as to expectation values calculated from free-electron laser physics. The model in conjunction with the high speed of the detectors permits the detection of an exponential rise time of the pulses as short as 5 ps despite a Gaussian post detection time constant of 11 and 14 ps for a large area and an antenna-coupled detector, respectively. This proves that field-effect transistors are excellent compact, room-temperature Terahertz detectors for applications that require an intermediate frequency bandwidth of several tens of GHz.

Abstract-Terahertz generation with ballistic photodiodes under pulsed operation

Stefan Malzer, Christian Müller-Landau, Heiko B Weber, Gottfried H Döhler, Stephan Winner,  Peter G Burke, Arthur Gossard,  Sascha Preu

http://iopscience.iop.org/article/10.1088/1361-6641/aae5e4

We investigate high field and ballistic carrier transport in a 1.55 μm photomixing
 device based on pin-diodes by time resolved terahertz (THz) spectroscopy. The device
 consists of 3 stacked In(Al)GaAs pin diodes (n-i-pn-i-p superlattice) attached to a
 broadband logarithmic-periodic antenna. Each pin diode is optimized for exhibiting
 ballistic transport and a reduced transit time roll-off. Ballistic transport signatures
 could be confirmed directly in these experiments. The data are compared with results
 from continuous-wave (CW) experiments and from simulations both supporting our
 theoretical expectations. It is demonstrated that n-i-pn-i-p superlattice photomixers
 are also efficient THz emitters under pulsed operation, showing a maximum THz field
 strength of ~0.5 V/cm (peak to peak) at 30 mW average optical power.

Abstract-Sensitivity limits of millimeter-wave photonic radiometers based on efficient electro-optic upconverters

Gabriel Santamaría Botello, Florian Sedlmeir, Alfredo Rueda, Kerlos Atia Abdalmalak, Elliott R. Brown, Gerd Leuchs, Sascha Preu, Daniel Segovia-Vargas, Dmitry V. Strekalov, Luis Enrique García Muñoz,  Harald G. L. Schwefel,

Fig. 1. Coupling of millimeter-wave and optical radiation to the WGM resonator. The microwave coupling region (enclosed by the dashed curve) is considered small and lossless. Input and output modes in the waveguide and the resonator are defined with normalized field amplitudes 𝑎𝑖(𝜈)$a_i(\nu )$ such that their squared norm equals the power spectral density of the mode. The coupling system can be viewed as a four-port network whose scattering matrix is characterized by the waveguide’s reflection coefficient 𝑟=𝑎2/𝑎1$r=a_2/a_1$ and waveguide-resonator transmission coefficient 𝑡=𝑎3/𝑎1$t=a_3/a_1$. The cavity’s reflection coefficient 𝑟′=𝑎3/𝑎4$r^{\prime }=a_3/a_4$ and cavity-waveguide transmission coefficient 𝑡′=𝑎2/𝑎4$t^{\prime }=a_2/a_4$ have the same magnitudes as 𝑟$r$ and 𝑡$t$, respectively, but a different phase in general

https://www.osapublishing.org/optica/abstract.cfm?uri=optica-5-10-1210

Conventional ultra-high sensitivity detectors in the millimeter-wave range are usually cooled as their own thermal noise at room temperature would mask the weak received radiation. The need for cryogenic systems increases the cost and complexity of the instruments, hindering the development of, among others, airborne and space applications. In this work, the nonlinear parametric upconversion of millimeter-wave radiation to the optical domain inside high-quality (𝑄$Q$) lithium niobate whispering-gallery mode (WGM) resonators is proposed for ultra-low noise detection. We experimentally demonstrate coherent upconversion of millimeter-wave signals to a 1550 nm telecom carrier, with a photon conversion efficiency surpassing the state-of-the-art by 2 orders of magnitude. Moreover, a theoretical model shows that the thermal equilibrium of counterpropagating WGMs is broken by overcoupling the millimeter-wave WGM, effectively cooling the upconverted mode and allowing ultra-low noise detection. By theoretically estimating the sensitivity of a correlation radiometer based on the presented scheme, it is found that room-temperature radiometers with better sensitivity than state-of-the-art high-electron-mobility transistor (HEMT)-based radiometers can be designed. This detection paradigm can be used to develop room-temperature instrumentation for radio astronomy, earth observation, planetary missions, and imaging systems.

© 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Abstract- Widely tunable telecom MEMS-VCSEL for terahertz photomixing

Mohammad Tanvir Haidar, Sascha Preu, Sujoy Paul, Christian Gierl, Julijan Cesar, Ali Emsia, and Franko Küppers,
https://www.osapublishing.org/ol/abstract.cfm?uri=ol-40-19-4428

We report frequency-tunable terahertz (THz) generation with a photomixer driven by an ultra-broadband tunable micro-electro-mechanical system vertical-cavity surface-emitting laser (MEMS-VCSEL) and a fixed-wavelength VCSEL, as well as a tunable MEMS-VCSEL mixed with a distributed feedback (DFB) diode. A total frequency span of 3.4 THz is covered in direct detection mode and 3.23 THz in the homodyne mode. The tuning range is solely limited by the dynamic range of the photomixers and the Schottky diode/photoconductor used in the experiment.

© 2015 Optical Society of America

Full Article  |  PDF Article

Abstract-Terahertz response of patterned epitaxial graphene

Christian Sorger, , Sascha Preu1,2, Johannes Schmidt3, Stephan Winnerl3, Yuliy V Bludov4, Nuno M R Peres4, Mikhail I Vasilevskiy4 and Heiko B Weber1

http://iopscience.iop.org/1367-2630/17/5/053045

heiko.weber@fau.de

1 Department of Physics, Friedrich-Alexander-University Erlangen-Nuremberg (FAU), Staudtstraße 7, D-91058 Erlangen, Germany
2 Department of Electrical Engineering and Information Technology, Technical University Darmstadt, Merckstraße 25, D-64283 Darmstadt, Germany
3 Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstraße 400, D-01314 Dresden, Germany
4 Department of Physics and Center of Physics, University of Minho, Campus de Gualtar, P-4710-057 Braga, Portugal 

We study the interaction between polarized terahertz (THz) radiation and micro-structured large-area graphene in transmission geometry. In order to efficiently couple the radiation into the two-dimensional material, a lateral periodic patterning of a closed graphene sheet by intercalation doping into stripes is chosen. We observe unequal transmittance of the radiation polarized parallel and perpendicular to the stripes. The relative contrast, partly enhanced by Fabry–Perot oscillations reaches 20%. The effect even increases up to 50% when removing graphene stripes in analogy to a wire grid polarizer. The polarization dependence is analyzed in a large frequency range from <80 GHz to 3 THz, including the plasmon–polariton resonance. The results are in excellent agreement with theoretical calculations based on the electronic energy spectrum of graphene and the electrodynamics of the patterned structure.

Abstract-Plasmonics enhanced photomixing for generating quasi-continuous-wave frequency-tunable terahertz radiation

Christopher W. Berry, Mohammad R. Hashemi, Sascha Preu, Hong Lu, Arthur C. Gossard, and Mona Jarrahi  »View Author Affiliations

Optics Letters, Vol. 39, Issue 15, pp. 4522-4524 (2014)
http://dx.doi.org/10.1364/OL.39.004522

http://www.opticsinfobase.org/ol/abstract.cfm?uri=ol-39-15-4522

We experimentally demonstrate an order of magnitude enhancement in the quasi-continuous-wave radiated power from a photomixer with plasmonic contact electrodes in comparison with an analogous conventional photomixer without plasmonic contact electrodes in the 0.25–2.5 THz frequency range when pumped at an optical wavelength of 1550 nm. The significant efficiency enhancement results from the unique capability of the plasmonic contact electrodes to reduce the average transport path of photocarriers to the device contact electrodes, increasing the ultrafast photocurrent that drives the terahertz antenna.

Abstract-Self-assembled ErSb nanostructures with optical applications in Infrared and Terahertz

Hong Lu , Daniel G. Ouellette , Sascha Preu , Justin D. Watts , Benjamin Zaks , Peter G. Burke , Mark S Sherwin , and Arthur Gossard

http://pubs.acs.org/doi/abs/10.1021/nl402436g?journalCode=nalefd

Nano Lett., Just Accepted Manuscript

DOI: 10.1021/nl402436g

Publication Date (Web): November 8, 2013

Copyright © 2013 American Chemical Society

Plasmonic effects have proven to be very efficient in coupling light to structures much smaller than its wavelength. Efficient coupling is particularly important for the infrared or terahertz (λ ~ 0.3 mm) region where semiconductor structures and devices may be orders of magnitude smaller than the wavelength and this can be achieved through nanostructures that have a desired plasmonic response. We report and demonstrate a self-assembly method of embedding controllable semimetallic nanostructures in a semiconducting matrix in a ErSb:GaSb material system grown by molecular beam epitaxy. The plasmonic properties of the ErSb:GaSb are characterized and quantified by three polarization-resolved spectroscopy techniques, spanning more than three orders of magnitude in frequency from 100 GHz up to 300 THz. Surface plasmons cause the semimetallic nanostructures to resonate near 100 THz (3 µm wavelength), indicating the semimetal as a potential infrared plasmonic material. The highly conductive ErSb nanowires polarize electromagnetic radiation in a broad range from 0.2 up to ~100 THz, providing a new platform for electromagnetics in the infrared and terahertz frequency ranges.