All-Optical Switching Demonstrated with Photoactive Yellow Protein Films

Abstract

Integrated optics (IO) is a field of photonics which focuses on manufacturing circuits similar to those in integrated electronics, but that work on an optical basis to establish means of faster data transfer and processing. Currently, the biggest task in IO is finding or manufacturing materials with the proper nonlinear optical characteristics to implement as active components in IO circuits. Using biological materials in IO has recently been proposed, the first material to be investigated for this purpose being the protein bacteriorhodopsin; however, since then, other proteins have also been considered, such as the photoactive yellow protein (PYP). In our current work, we directly demonstrate the all-optical switching capabilities of PYP films combined with an IO Mach–Zehnder interferometer (MZI) for the first time. By exploiting photoreactions in the reaction cycle of PYP, we also show how a combination of exciting light beams can introduce an extra degree of freedom to control the operation of the device. Based on our results, we discuss how the special advantages of PYP can be utilized in future IO applications.

Penetration of the SARS-CoV-2 Spike Protein across the Blood–Brain Barrier, as Revealed by a Combination of a Human Cell Culture Model System and Optical Biosensing

“…The sensor devices used in this study were fabricated and improved based on the construction of the integrated optical MZI interferometer biosensor described in detail in a previous study of our research group [ 22 ]. The waveguide structure was made by direct laser writing technique (μPG-101 machine, , Heidelberg Instruments GmbH, Heidelberg, Germany), as was previously described [ 23 ].…”

“…A microfluidic channel was fabricated and integrated in the final form of the sensor device to work with fluid samples [ 24 ]. As in our previous study [ 22 ], heating was used for setting the bias point prior to the measurements by applying DC voltage on a substrate-bound 20 nm thick gold microheater structure. To improve its adherence to the substrate 10 nm thick Cr was deposited followed by the deposition of the desired gold layer, as was described in one of our latest works [ 23 ].…”

“…Prior to the measurements, higher and lower flow rates were applied for filling up the microchannels with the buffer or target protein solutions (30 μL/min and 3 μL/min, respectively). As a starting point of the experiments, the bias point of the integrated optical MZI was adjusted, as has been described previously in detail [ 22 ]. To obtain valid detection results by the interferometer, the signal levels and the phase-shifting effect of the microheater at a given applied voltage were set ( Figure S1 ); therefore, output signals obtained from distinct sensors possessing slightly different sensitivities are comparable.…”

Ultrafast All-Optical Switching Using Doped Chromoprotein Films

“…400 and 650 nm) as compared to PYP (between ca. 360 and 500 nm), while PYP, being a relatively small, water-soluble protein compared to BR that is available embedded in large membrane fragments, can be easily combined with nanostructured materials which makes it a suitable candidate as an active element in IO devices. , Finally, the excited-state concentration grating employed in our scheme may also be used as an optically controlled diffractive element in future wavelength-selective switches.…”

“…In contrast to BR, PYP is a small, water-soluble protein offering much more straightforward incorporation into passive structures. Accordingly, the NLO properties of PYP films have recently been characterized , and shown promise for use in integrated optical modulators . Nevertheless, utilization of the sub-picosecond photoreaction of the PYP photocycle , for ultrafast all-optical switching has not been accomplished so far.…”