Optical sidebands are generated by difference frequency mixing between a resonant bandgap near-infrared beam and a terahertz (THz) wave. This is realized within the cavity of a THz quantum cascade laser using resonantly enhanced non-linearities. Multiple order optical sidebands and conversion efficiencies up to 0.1% are shown

Beere, HE

Cavalié, P

Colombelli, R

Davies, AG

Dhillon, SS

Freeman, J

Li, L

Linfield, EH

Madéo, J

Mangeney, J

Maussang, K

Ritchie, DA

Sirtori, C

Strupiechonski, E

Tignon, J

Xu, G

White Rose Research Online

This is a repository copy of High order optical sideband generation with Terahertz quantumcascade lasers.White Rose Research Online URL for this paper:http://eprints.whiterose.ac.uk/83255/Version: Accepted VersionProceedings Paper:Cavalié, P, Madéo, J, Freeman, J et al. (13 more authors) (2013) High order optical sideband generation with Terahertz quantum cascade lasers. In: International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz. International Conference on Infrared, Millimeter, and Terahertz Waves, 1-6 September 2013, Mainz, Germany. IEEE . ISBN 9781467347174 https://doi.org/10.1109/IRMMW-THz.2013.6665599eprints@whiterose.ac.ukhttps://eprints.whiterose.ac.uk/Reuse Unless indicated otherwise, fulltext items are protected by copyright with all rights reserved. The copyright exception in section 29 of the Copyright, Designs and Patents Act 1988 allows the making of a single copy solely for the purpose of non-commercial research or private study within the limits of fair dealing. The publisher or other rights-holder may allow further reproduction and re-use of this version - refer to the White Rose Research Online record for this item. Where records identify the publisher as the copyright holder, users can verify any specific terms of use on the publisher’s website. Takedown If you consider content in White Rose Research Online to be in breach of UK law, please notify us by emailing eprints@whiterose.ac.uk including the URL of the record and the reason for the withdrawal request. High order optical sideband generation with Terahertz quantum cascade lasers P. Cavaliel*, J. Madeol, J. Freemanl, K. Maussangl, E. Strupiechonski,2 G. XU,2 R. Colombelli2, H. E. Beere3, D. A. Ritchie3, L. Li,4 A. G. Davies,4 E. H. Linield4, C. SirtoriS, J. Mangeney/ J. Tignonl and S. S. Dhillonl lLaboratoire Pierre Aigrain, Ecole Normale Superieure, CNRS (UMR 8551), Universite Paris P. et M. Curie, Universite D. Diderot, 75231 Paris Cedex 05, France 2Institut d'Electronique Fondamentale, University Paris Sud, UMR8622 CNRS, 91405 Orsay, France. 3Semiconductor Physics, Cavendish Laboratory, University of Cambridge, United Kingdom 4School of Electronic and Electrical Engineering, University of Leeds, Leeds LS9 2JT, United Kingdom. S Materiaux et Phenomene Quantique, Universite Paris 7, 75205 Paris cedex 13, France Email: pierrick.cavalie@lpa.ens.r Abstract - Optical sidebands are generated by difference frequency mixing between a resonant bandgap near-infrared beam and a terahertz (THz) wave. This is realized within the cavity of a THz quantum cascade laser using resonantly enhanced non-linearities. Multiple order optical sidebands and conversion eiciencies up to 0.1 % are shown. The nonlinear optical properties of intersubband and interband transitions in quantum wells has recently received considerable attention owing to their enhanced susceptibilities compared to bulk properties and potential applications in devices such as optical switches and modulators. Indeed eficient non-linear wave mixing between a near-inrared probe (interband resonance) in presence of an intense terahertz (THz) beam (intersubband resonance) in quantum wells systems has been already demonstrated [1,2]. However, the THz radiation was provided by a Free Electron Laser (FEL). In this work, we demonstrate [3] that these types of high order nonlinear processes can be realized using the resonant interband nonlinearities of a compact and practical device - the quantum cascade laser (QCL) [4]. Figure 1 a shows a schematic of the process. The THz QCL laser transition EQCL occurs within the conduction band between the highlighted green states (Eu-En). A near-inrared beam (NIR) ENIR is coupled into the QCL cavity resulting in a bandgap excitation rom the conined hole state. The geometry results in a resonance enhancement of the second order non­linearity permitting non-linear requency mixing. As a result the difference requency ENIR-EQCL is generated via a virtual state below the bandgap and is therefore not absorbed. This concept permitted the generation of the difference requency at ENlR-QCL= l.5171 eV (,=817nm) with ENIR=1.53eV, i.e. separated rom the pump ENiR by exactly the photon energy of the THz QCL (operating at =2.78 THz, EQcL�12meV). When the QCL is taken above laser threshold, the difference requency is observed for pump excitations over a range of few meV (1.523eV < ENIR < 1.534eV). A resonant behaviour is found for the conversion eiciency with a maximum of 0.13% observed for pump energies of 1.527eV, comparable to those obtained in FEL experiments [3]. We have also demonstrated high order terahertz (THz) requency sidebands (up to 3rd order) within the THz QCL i.e. ENlR±nEQCL with integer n> 1. This was achieved with a double metal QCL cavity to enhance the intracavity power density, approaching those used in FEL studies. Figure Ib shows the typical sideband spectra observed with the QCL above laser threshold. Each sideband was investigated as a unction of THz input power. The 15t order sideband intensity shows a linear dependence with THz power corresponding to a single THz photon, while the second order sideband has a quadratic dependence implying a two THz photon interaction and hence a third order susceptibility. We show that the irst and second order sidebands correspond to an enhanced second and third order susceptibility, respectively, that are two orders of magnitude greater than the bulk value. The perspectives of this work include tuning the interband resonances to the telecom window using mid-inrared InP­based QCLs. The latter operate at room temperature and would allow wavelength shiting between different telecommunication bands. Conduction Band 6000 :l � 4000 � 'ii c $ 2000 c X 100 o JL -Pump -1stOrder -2nd Order 1.500 1.505 1.510 1.525 1.53 Energy (e) (a) (b) Fig. 1a) Schematic of the resonant non-linear process for the generation of the diference frequency (ENIR - EQcd in a QCL operating at EQCL. A NIR pump ENIR is tuned in resonance with interband transitions. This allows the generation of a lower energy beam at ENIR-EQCL via a virtual state below the material bandgap. b) Pump laser spectrum through QCL and spectrum of the below bandgap generated sidebands at the generated diferences, ENIR-EQCL and ENIR-2EQCL. The third order sideband ENIR-3EQCL is shown in the inset. EFERENCES [I] S. G. Carter et aI., App. Phys. Lett. 84, 840-843, 2004 [2] B. Zaks et aI, Nature 83,580,2012. [3] J. Madeo et ai, Nature Photonics, 6,519-524,2012 [4] R. Kohler et aI., Nature 417,156-159,2002 

High order optical sideband generation with Terahertz quantum cascade lasers

P. Cavalie

J. Madeo

J. Freeman

K. Maussang

E. Strupiechonski

G. Xu

R. Colombelli

H. E. Beere

D. A. Ritchie

L. Li

A. G. Davies

E. H. Linfield

C. Sirtori

J. Mangeney

J. Tignon

S. S. Dhillon

Crossref

Cavalié, P.

Madéo, J.

Freeman, J.

Maussang, K.

Strupiechonski, E.

Xu, G.

Colombelli, R.

E. Beere, H.

Ritchie, D.A.

Li, L.

G. DAVIES, A.

H. Linfield, E.

Sirtori, C.

Mangeney, J.

Tignon, J.

S. Dhillon, S.

Hal-Diderot

https://eprints.whiterose.ac.uk/83255/1/Cavalie%20et%20al%20High%20order%20optical%20sideband%20generation.pdf

High order optical sideband generation with Terahertz quantum cascade lasers

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