13 research outputs found
Photon-pair sources based on intermodal four-wave mixing in few-mode fibers
Four-wave mixing in optical fibers has been proven to have many applications within processing of classical optical signals. In addition, recent developments in multimode fibers have made it possible to achieve the necessary phase-matching for efficient four-wave mixing over a very wide bandwidth. Thus, the combination of multimode fiber optics and four-wave mixing is very attractive for various applications. This is especially the case for applications in quantum communication, for example in photon-pair generation. This is the subject of this work, where we discuss the impact of fluctuations in core radius on the quality of the heralded single-photon states and demonstrate experimental results of intermodal spontaneous four-wave mixing for photon-pair generation
Unidirectional frequency conversion in microring resonators for on-chip frequency-multiplexed single-photon sources
Microring resonators are attractive for low-power frequency conversion via
Bragg-scattering four-wave-mixing due to their comb-like resonance spectrum.
However, conversion efficiency is limited to 50% due to the equal probability
of up- and down-conversion. Here, we demonstrate how two coupled microrings
enable highly directional conversion between the spectral modes of one of the
rings. An extinction between up- and down-conversion of more than 40 dB is
experimentally observed. Based on this method, we propose a design for on-chip
multiplexed single-photon sources that allow localized frequency modes to be
converted into propagating continuous-mode photon wave packets using a single
operation. The key is that frequency conversion works as a switch on both
spatial and spectral degrees of freedom of photons if the microring is
interferometrically coupled to a bus waveguide. Our numerical results show 99%
conversion efficiency into a propagating mode with a wave packet having a 90%
overlap with a Gaussian for a ratio between intrinsic and coupling quality
factors of 400
Experimental characterization of Raman overlaps between mode-groups
Mode-division multiplexing has the potential to further increase data transmission capacity through optical fibers. In addition, distributed Raman amplification is a promising candidate for multi-mode signal amplification due to its desirable noise properties and the possibility of mode-equalized gain. In this paper, we present an experimental characterization of the intermodal Raman intensity overlaps of a few-mode fiber using backward-pumped Raman amplification. By varying the input pump power and the degree of higher order mode-excitation for the pump and the signal in a 10 km long two-mode fiber, we are able to characterize all intermodal Raman intensity overlaps. Using these results, we perform a Raman amplification measurement and demonstrate a mode-differential gain of only 0.25 dB per 10 dB overall gain. This is, to the best of our knowledge, the lowest mode differential gain achieved for amplification of mode division multiplexed signals in a single fiber
High coincidence-to-accidental ratio continuous-wave photon-pair generation in a grating-coupled silicon strip waveguide:Letters
Complete evolution equation for the joint amplitude in photon-pair generation through spontaneous four-wave mixing
As four-wave-mixing-based photon-pair sources mature, accurate modelling of
the photon-pair properties becomes important. Unlike spontaneous parametric
down-conversion, four-wave mixing is accompanied by a number of parasitic
effects such as nonlinear phase modulation. Currently, most modelling of
photon-pair states are analytic in nature, which limits the number and type of
effects that can be taken into account. In this work, we derive a complete,
dual-pump evolution equation for the joint amplitude of photon pairs, wherein
any desired effects can be included. We describe how to efficiently obtain
numerical solution to this equation using a split-step approach. Lastly, we
cover a few analytical solutions and compare two schemes for pure-photon
generation under three different parasitic effects. We show how one scheme is
highly sensitive to parasitic effects, while the other is very robust.Comment: 7 pages, 5 figure
Mode entanglement using multiple orbital angular momentum modes
We consider the potential for generating photon pars with high-dimensional entanglement in their orbital angular momentum through multiple simultaneous four-wave-mixing processes. We study a realistic fiber design and show that states with high entanglement negativity may be obtained