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Parametric generation in semiconductor microstructures

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Our research on this axis is focused on the demonstration of new schemes of CW optical frequency generation, parametric generation and parametric amplification, based on the bulk nonlinear coefficient of AlGaAs. Our sources operate at room temperature from near to far IR, and they rely on different phase-matching (PM) techniques developed by our group. Here we highlight the main results concerning : 1) parametric generators in the near and mid IR, based on partially oxidized waveguides ; 2) active microrings for the difference-frequency generation (DFG) of THz radiation, with pump fields the telecom band ; 3) suspended AlGaAs microdisks for second harmonic generation (SHG) ; and 4) narrow-ridge quantum dot lasers for spontaneous parametric down-conversion.

Parametric generators based on partially oxidized waveguides

The sources of this type, fabricated by lateral oxidation of AlGaAs/AlAs heterostructures, can be phase-matched via the form birefringence induced by the index contrast between AlGaAs and aluminum oxide (AlOx). Thanks to this technique, we have achieved record efficiencies of semiconductor waveguides for both degenerate parametric generation at 2 µm [1] and SHG with 1.55 µm pump wavelength [2]. More recently, with a pump around 1 µm and signal and idler around 2 µm, we have demonstrated an optical parametric oscillator (OPO) with an oscillation threshold of 210 mW at degeneracy in the continuous-wave regime, with a single-pass-pump doubly resonant scheme [3]. This result represents a significant milestone in the perspective of an electrically injected OPO on chip, which stays a major goal of photonic research, after more than 50 years from the birth of nonlinear optics. This delay is basically due to the difficulty of combining efficient PM schemes with low optical losses. In the case of AlOx waveguides, we have singled out two regimes for the losses, in collaboration with the MEANS team and LPN : 1) for photon energies lower than 70% of AlGaAs bandgap, such losses are dominated by the roughness-induced diffusion at AlGaAs/AlOx interfaces ; 2) for energies closer to the gap, they increase exponentially and are dominated by Urbach tails due bulk defects that are induced in the crystal lattice during the oxidation process [4, 5].

A post-doc position is currently available on this research axis.


Active microrings for THz DFG

The second source combines the high nonlinearity of AlGaAs and the strong optical confinement in high-Q whispering-gallery-mode (WGM) resonators. Our concept has already made the object of two joint MPQ-CEA patents, and it relies on the PM granted by both anomalous dispersion around the Restrahlen Band and a purely geometric quasi-PM scheme. This source will contain two layers of quantum dots (QDs) emitting at around 1.25 µm and promises several advantages with respect to existing CW THz sources (like photomixers and quantum cascade lasers) : compact size ; room-temperature operation ; continuous-wave output power scalable to the microwatt range ; customized emission frequency from 1 to 4 THz ; up-scaling of the emitted power via 2D arrays ; feasibility of multi-spectral array of emitters ; and perspective of coherent detection [6]. During the past three years we have been coordinating a high-level consortium within the EU FP7 FET TREASURE project, including top-class partners like CEA and the University of Würzburg, in charge of MBE growth and fabrication. Among the most recent results in this project, let us cite the room-temperature WGM low-threshold lasing of the QDs around 1.25 µm, the design of a tool for the fine-tuning tool of the PM condition [7], and the multi-spectral characterization of the WGM resonator [8].


Suspended AlGaAs microdisks for SHG

The third source exploits the high optical confinement and modal overlap provided by suspended microdisks. Some experimental studies had already reported on SHG in GaAs WGM microcavities. However, the GaAs does not allow working with a pump wavelength in the telecom range. Therefore, to make these devices more attractive for technological applications, we have designed AlGaAs microdisks - suspended on a GaAs pedestal - for SHG with a pump wavelength around 1550 nm. The microdisks fabrication has required intensive technological efforts [9], but the first samples have been successfully fabricated and are now being characterized via evanescent coupling with silica tapered fibers.

An internship position is currently available on this research axis.


Narrow-Ridge Quantum Dot Lasers for Spontaneous Parametric Down-Conversion

This fourth axis aims at demonstrating the first electrically pumped OPO by exploiting intracavity parametric down-conversion within a narrow-ridge QD laser diode.
The main advantage of using QDs is related to their ability to trap charge carriers and quench diffusion toward non-radiative recombination centers, as shown since the mid 90’s for QDs in dislocated material. This unique property of QD active media allows the fabrication of deeply etched narrow-stripe (2-3 μm) laser diodes with threshold current densities comparable to those of broad area devices. The width of such waveguides provides a key degree of freedom for fulfilling the phase matching condition. Together with our collaborators at CEA Grenoble we have recently reported on extensive transport and electromagnetic simulations concerning such devices, showing good laser performance and high nonlinear conversion efficiencies [10].

An internship position is currently available on this research axis.


References

[1] E. Guillotel, M. Ravaro, F. Ghiglieno, C. Langlois, C. Ricolleau, S. Ducci, I. Favero, and G. Leo, "Optical parametric amplification in GaAs/AlOx waveguide", Appl. Phys. Lett. 94, 171110 (2009).

[2] M. Savanier, A. Andronico, A. Lemaître, E. Galopin, C. Manquest, I. Favero, S. Ducci, and G. Leo, "Large Second-Harmonic Generation at 1.55 μm in oxidized AlGaAs waveguides", Opt. Lett. 36, 2955 (2011).

[3] M. Savanier, C. Ozanam, L. Lanco, X. Lafosse, A. Andronico, I. Favero, S. Ducci, and G. Leo, "Near-infrared optical parametric oscillator in a III-V semiconductor waveguide", Appl. Phys. Lett., in press.

[4] E. Guillotel, C. Langlois, F. Ghiglieno, G. Leo, and C. Ricolleau, "TEM characterization of oxidized AlGaAs/AlAs nonlinear optical waveguides", J. Phys. D : Appl. Phys. 43, 385302 (2010).

[5] M. Savanier, A. Andronico, A. Lemaître, C. Manquest, I. Favero, S. Ducci, and G. Leo, "Nearly-degenerate three-wave mixing at 1.55 μm in oxidized AlGaAs waveguides", Opt. Express 19, 22582 (2011).

[6] A. Andronico, J. Claudon, J.-M. Gérard, V. Berger, and G. Leo, "Integrated terahertz source based on three-wave mixing of whispering-gallery modes", Opt. Lett., 33, 2416 (2008).

[7] A. Andronico, S. Mariani, F. Ghiglieno, J. Claudon, M. Munsch, J. M. Gérard, I. Favero, S. Ducci, and G. Leo, "Tuning of a nonlinear THz emitter", Opt. Express 20, 17678 (2012).

[8] S. Mariani, A. Andronico, I. Favero, S. Ducci, Y. Todorov, C. Sirtori, M. Kamp, M. Munsch, J. Claudon, J. M. Gérard, T. Wang, P. U. Jepsen, and G. Leo, "Microring Diode Laser for THz Generation", IEEE Trans. THz Sci. Technol. 3, 472 (2013).

[9] S. Mariani, A. Andronico, O. Mauguin, A. Lemaître, I. Favero, S. Ducci, and G. Leo, "AlGaAs microdisk cavities for second-harmonic generation", Opt. Lett. 38, 3965 (2013).

[10] A. Andronico, I. Favero, S. Ducci, J. M. Gérard, and G. Leo, "Tunable quantum dot parametric source", Opt. Express 21, 22367 (2013).