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Uncovering dispersion properties in semiconductor waveguides to study photon-pair generation

Laiho, K., Pressl, B., Schlager, A., Suchomel, H., Kamp, M., Sven Höfling, Schneider, C., Gregor Weihs

Published Jan 1, 2016• 6 citations
OpenAlex

Abstract

We investigate the dispersion properties of ridge Bragg-reflection waveguides to deduce their phasematching characteristics. These are crucial for exploiting them as sources of parametric down-conversion (PDC). In order to estimate the phasematching bandwidth we first determine the group refractive indices of the interacting modes via Fabry-Perot experiments in two distant wavelength regions. Second, by measuring the spectra of the emitted PDC photons, we gain access to their group index dispersion. Our results offer a simple approach for determining the PDC process parameters in the spectral domain, and provide important feedback for designing such sources, especially in the broadband case.

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We investigate the dispersion properties of ridge Bragg-reflection waveguides to deduce their phasematching characteristics. These are crucial for exploiting them as sources of parametric down-conversion (PDC). In order to estimate the phasematching bandwidth we first determine the group refractive indices of the interacting modes via Fabry-Perot experiments in two distant wavelength regions. Second, by measuring the spectra of the emitted PDC photons, we gain access to their group index dispersion. Our results offer a simple approach for determining the PDC process parameters in the spectral domain, and provide important feedback for designing such sources, especially in the broadband case.
We investigate the dispersion properties of ridge Bragg-reflection waveguides to deduce their phasematching characteristics. These are crucial for exploiting them as sources of parametric down-conversion (PDC). In order to estimate the phasematching bandwidth we first determine the group refractive indices of the interacting modes via Fabry-Perot experiments in two distant wavelength regions. Second, by measuring the spectra of the emitted PDC photons, we gain access to their group index dispersion. Our results offer a simple approach for determining the PDC process parameters in the spectral domain, and provide important feedback for designing such sources, especially in the broadband case.
Bragg-reflection waveguides (BRWs) fabricated from AlGaAs provide an interesting nonlinear optical platform for photon-pair generation via parametric down-conversion (PDC). In contrast to many conventional PDC sources, BRWs are made of high refractive index materials and their characteristics are very sensitive to the underlying layer structure. First, we show that the design parameters like the phase matching wavelength and the group refractive indices of the interacting modes can be reliably controlled even in the presence of fabrication tolerances. We then investigate how these characteristics can be taken advantage of when designing quantum photonic applications with BRWs. We especially concentrate on achieving a small differential group delay between the generated photons of a pair and then explore the performance of our design when realizing a Hong–Ou–Mandel interference experiment or generating spectrally multi-band polarization entangled states. Our results show that the versatility provided by engineering the dispersion in BRWs is important for employing them in different quantum optics tasks.
This work investigated the spectral properties and state fidelity of photons generated by spontaneous parametric down-conversion in AlGaAs Bragg-reflection waveguides. Effective refractive indices, group indices, their dispersion, and their influence on the spectral properties of the down-converted photons were evaluated by simulation and characterization of fabricated waveguides. A comparison was made between two different types of waveguides differing in the ridge width, specifically narrow ridges of ∼1.7-1.9 μm and wide ridges of ∼4 μm. The group indices for the down-converted and pump photons were determined by Fabry-Pérot measurements. Group indices dispersion and the ratio between the group indices of signal and idler photons as well as the expected state fidelity were extracted from measured spectra of the down-converted photons. Additionally, the fidelity to the Bell state was determined by quantum state tomography. For larger Δ n g we observe substantial deviation between theoretical spectra and fidelity beyond the experimental uncertainties.
Parametric downconversion (PDC) in semiconductor Bragg-reflection waveguides (BRW) is routinely exploited for photon-pair generation in the telecommunication range. Contrary to many conventional PDC sources, BRWs offer possibilities to create spectrally broadband but nevertheless indistinguishable photon pairs in orthogonal polarizations that simultaneously incorporate high frequency entanglement. We explore the characteristics of co-propagating twin beams created in a type-II ridge BRW. Our PDC source is bright and efficient, serving as a benchmark of its performance and justifies its exploitation for further use in quantum photonics. We then examine the coalescence of the twin beams and investigate the effect of their inevitable multi-photon contributions on the observed photon bunching. Our results show that BRWs have a great potential for producing broadband indistinguishable photon pairs as well as multi-photon states.
In this paper, we present Bragg reflection waveguides as a novel universal platform for reaching the phasematching of spontaneous parametric downconversion process in semiconductor materials. We have designed two different waveguide structures. The first one is based on AlGaN and it is able to produce spectrally uncorrelated photon pairs. The second one is based on AlGaAs and it allows us to generate entangled photon pairs with ultra-broad spectra. Spontaneous-parametric-downconversion and second-harmonic-generation experiments are presented.
Bragg reflection waveguides are considered as monolithic sources of frequency correlated photon pairs generated using spontaneous-parametric down-conversion in a AlxGa1-xAs material system. The source described here offers unprecedented control over the process bandwidth, enabling bandwidth tunability between 1 nm and 450 nm while using the same wafer structure. This tuning is achieved by exploiting the powerful control over the waveguide dispersion properties afforded by the phase-matching technique used. The offered technology provides a route for realizing electrically pumped, monolithic photon pair sources on a chip with versatile characteristics.