Raman analysis of the crystallinity degree for the local regions in Ge2Sb2Te5 films after laser exposure at different parameters

The evaluation of the crystallinity degree for the local regions in Ge2Sb2Te5 (GST) thin films after phase state transformation by laser pulses at 405 nm wavelength was analyzed using the Raman spectroscopy. The modes of laser radiation for controlling the reflectivity and transmissivity at 1550 nm telecommunication wavelength of the local regions in the GST film were established. The results obtained make it possible to implement the method of the completely optical control of the multilevel modulation of the optical signals for the integrated optics devices.

Optical Constants of rare-Earth Substituted Ferrite-Type Amorphous Garnets and Nanoscale Garnet-Oxide Layers

Amorphous ferrite-type rare-earth (RE) substituted garnets and garnet-oxide nanocomposite layers are prepared on clear glass substrates by using RF magnetron sputter-deposition process. By using a combination approach employing custom-built spectrum-fitting software in conjunction with Swanepoel’s envelope method, the spectral dispersion function of optical constants and the layer thicknesses are derived accurately from the transmission spectra of the as-deposited samples. The effects of excess metal-oxides added to the base material systems during the co-deposition process are found to affect the refractive index and the optical absorption coefficients of garnet-oxide composites. A number of optical constant datasets are presented, enabling the experimentalists to design nanophotonic or integrated-optics devices employing these functional materials.

Harnessing temporal modes for multi-photon quantum information processing based on integrated optics

In the last few decades, there has been much progress on low loss waveguides, very efficient photon-number detectors and nonlinear processes. Engineered sum-frequency conversion is now at a stage where it allows operation on arbitrary temporal broadband modes, thus making the spectral degree of freedom accessible for information coding. Hereby the information is often encoded into the temporal modes of a single photon. Here, we analyse the prospect of using multi-photon states or squeezed states in different temporal modes based on integrated optics devices. We describe an analogy between mode-selective sum-frequency conversion and a network of spatial beam splitters. Furthermore, we analyse the limits on the achievable squeezing in waveguides with current technology and the loss limits in the conversion process. This article is part of the themed issue ‘Quantum technology for the 21st century’.

Loss Compensation in Surface Plasmonic Waveguides with Low Polarization Dependence

Surface plasmonic waveguides usually only support one mode called TM (transverse magnetic) mode. Recently, one waveguide structure that can propagate both TE (transverse electric) and TM mode was proposed. However, the large propagation loss of the plasmonic waveguides with low polarization dependence is still a problem. In order to make loss compensation to solve the problem, this paper makes improvements to decrease the loss of this kind of waveguide. Simulations have been made to prove the feasibility; as respected, low loss or even 0dB can be reached at both modes when low and high index materials are added. The improved plasmonic waveguide has a potential application in guiding and processing of light from a fiber with a random polarization state in low-loss condition and also can be applied to integrated optics devices.