Quantum Optics

Dr. habil. Frank SETZPFANDT

Email: f.setzpfandt@uni-jena.de
Phone: +49 3641 947569

Since 2016, Dr. Setzpfandt leads a Research Group focused on quantum optics, especially targeting quantum imaging and sensing approaches, as well as integrated quantum optics. Before, he was a PostDoc at the Institute of Applied Physics of the Friedrich Schiller University and the Nonlinear Physics Centre of the National University Canberra, Australia. He currently serves as CEO of the Thuringian Innovation Center for Quantum Optics and Sensors.

The research group for quantum optics at the Institute of Applied Physics is focusing on the generation of non-classical states of light and their application using theoretical and experimental approaches. Mainly, we are studying the generation of photon pairs by spontaneous nonlinear processes in various nonlinear photonic systems ranging from bulk crystals over different waveguide structures to nanostructured or atomically thin surfaces. We aim to fundamentally understand the nonlinear effects leading to photon-pair generation and how they depend on the material and geometry of the sources. We use this understanding to tailor the properties of the generated two-photon quantum states, like spectrum, spatial distribution, and entanglement, to meet the demands of specific applications. Furthermore, we investigate the application of photon pairs for quantum-enhanced imaging and spectroscopy techniques, where they can enable measurements with better signal-to-noise ratio or in hardly accessible wavelength ranges. Our research on one hand tries to understand fundamental aspects of quantum measurements, including the interaction of the photons with the samples under test, to develop new imaging and spectroscopy methods. On the other hand, we aim at bringing quantum imaging and spectroscopy closer towards applications by developing integrated measurement devices.

Research Areas

The research of Dr. Setzpfandt focuses on the generation of tailored classical and nonclassical states of light using nanostructured and integrated optical systems as well as the use of nonclassical light for imaging and sensing. This includes the following research fields:

Integrated quantum optics
Nonlinear optics in waveguide and nanostructures
Photon-pair generation
Quantum imaging and sensing

Teaching Fields

Dr. Setzpfandt currently teaches master-level courses on:

Quantum Optics
Quantum Imaging and Sensing

Research Methods

Dr. Setzpfandt uses a number of state-of-the-art characterization techniques, e.g.:

Nonlinear frequency conversion and nonlinear spectroscopy
Photon-pair correlation measurements
Quantum ghost imaging
Integrated optical circuit characterization

Recent Research Results

Waveguides for quantum spectroscopy.
Illustration: Setzpfandt research group

Photon pairs, quantum states of light containing exactly two photons, are the basis for many quantum phenomena and quantum applications in computing, communication, and sensing. They are often generated using spontaneous down-conversion (SPDC), a second-order nonlinear conversion process where a shortwavelength pump photon decays into a pair of signal and idler photons. The properties of these photon pairs can be controlled to a large extent by the properties of the nonlinear optical material they are generated in. One focus of our research is to use structured nonlinear materials in the form of waveguides or nanophotonic resonators to generate tailored photon pairs, where we could show the generation of spatially entangled pairs in nanostructured waveguides [1] and develop a complete understanding of the states that can be generated in coupled waveguide systems [2]. Furthermore, we could show that waveguide sources of photon pairs can be directly used as a spectroscopic sensor, where, using quantum correlations, spectroscopy in the mid-IR can be performed by measuring only photons in the visible [3, 4].

We also investigate the applications of photon pairs for quantum imaging, where we recently found a lensless quantum imaging method reminiscent of a pinhole camera [5].

Whereas nonlinear waveguides are an established platform for generating photon pairs, nanostructured nonlinear surfaces are currently emerging and enable precise control of the emission direction of photon pairs by lateral structuring. The potential of this approach was demonstrated for a surface of monomolecular thickness using classical frequency conversion, which follows the same rules as SPDC [6].

[1] Saravi et al., Opt. Lett. 44, 69 (2019).
[2] Belsley et al., Opt. Express 28, 28792 (2020).
[3] Kumar et al., Phys. Rev. A 101, 053860 (2020).
[4] Solntsev et al., APL Photonics 3, 021301 (2018).
[5] Vega et al., Appl. Phys. Lett. 117, 094003 (2020).
[6] Löchner et al., Opt. Express 27, 35475 (2019).

Link to the Quantum Optics Group at the Institute of Applied Physics