Photonics technology benefits when a beam of light can be manipulated without distorting its phase and intensity profile. This means that even after manipulation the information embedded in the beam do not get loss or jumbled. Recently, an orbital angular momentum carrying beam has gained attention because of the promise of sub-wavelength resolution nano-optics and free-space communication of both classical and quantum light beams. Manipulating such beams provides an opportunity for various novel applications.
In this publication, we converted orbital angular momentum carrying beams to have a different color using sum-frequency conversion in a periodically poled lithium niobate crystal. We observe that the frequency-converted beams exhibit a high degree of similarity with the input beam. We also verify the coherence of the frequency-conversion process. Coherence conversion is crucial for interfacing information stored in the high-dimensional spatial structure of single and entangled photons with various constituents of quantum networks.
Our results demonstrate the suitability of exploiting the technique for applications in quantum information processing and coherent imaging.
This research is a collaboration between several research institutions and universities. ICFO is a leading research institute for optics and photonics research while IQOQI is the leading institute for quantum optics and its applications. Experiments were done at the ICFO, Barcelona, Spain.
Steinlechner, F. et al. Frequency conversion of structured light. Sci. Rep. 6, 21390; doi: 10.1038/srep21390 (2016).