Integrated polarization-sensitive amplification system for digital information transmission

Polarized light can provide significant information about objects, and can be used as information carrier in communication systems through artificial modulation. However, traditional polarized light detection systems integrate polarizers and various functional circuits in addition to detectors, and are supplemented by complex encoding and decoding algorithms. Although the in-plane anisotropy of low-dimensional materials can be utilized to manufacture polarization-sensitive photodetectors without polarizers, the low anisotropic photocurrent ratio makes it impossible to realize digital output of polarized information. In this study, we propose an integrated polarization-sensitive amplification system by introducing a nanowire polarized photodetector and organic semiconductor transistors, which can boost the polarization sensitivity from 1.24 to 375. Especially, integrated systems are universal in that the systems can increase the anisotropic photocurrent ratio of any low-dimensional material corresponding to the polarized light. Consequently, a simple digital polarized light communication system can be realized based on this integrated system, which achieves certain information disguising and confidentiality effects.

der Waals forces in the b-axis. Therefore, at the edge of Bi2Se2S, the bonding force between atoms along the a-axis is stronger than that along the b-axis, which leading that the Bi2Se2S tends to grow along the a-axis. The anisotropic crystal structure makes it easier for Bi2Se2S to form NWs morphology during the growth process and preferentially grow along the a-axis. As shown in Supplementary Fig. 2b, the SEM image further demonstrates that the morphology of the growing material is similar to NWs and the diameter is less than 1 m. In order to analyze the crystal structure of Bi2Se2S NW, HRTEM of the NW is characterized (Supplementary Fig. 2c). At this zone axis and defocus amount slightly, it can be seen that the NW has two crystal planes (0 2 0) and ( 1 3 0), which corresponding lattice spacing is 5.821 Å and 3.842 Å, respectively.
This result further proves that the NWs preferentially grow along the a-axis. The secondary growth axis is the b-axis. When linearly polarized light is irradiated on the surface of the material, the structure anisotropy of the a-axis and b-axis of the Bi2Se2S NW will be main factor affecting the anisotropic photocurrent of the material. The EDS element mapping corresponding to the TEM image is shown in Supplementary Fig. 3, demonstrating that the three elements of Bi, Se and S are uniformly distributed in the NW. This illustrates that the grown Bi2Se2S NWs are of high quality and crystallinity.

Supplementary Note 2
According to the classical theory, the Raman scattering intensity of the crystal can be expressed as: where I is the Raman scattering intensity, hs and hi are the polarization direction vector of the incident laser and scattered laser, respectively, R is the Raman tensor. According to the previous inference, since the Bi2Se2S NWs grow along the a-b plane and stack along the c-axis, the incident light is irradiated to the ab plane of the Bi2Se2S NWs along the c-axis. Therefore, the corresponding hs and hi can be defined as: where h_(s∥) and h_(s⊥) correspond to the polarization direction of scattered laser in parallel and cross configurations, respectively. θ represents the angle between the polarization direction of the incident light and the a-axis. Because the space group of Bi2Se2S is Pbnm and the point group is 2ℎ 16 , its Raman tensor are mean as: The results reveal that when the laser is irradiated to the Bi2Se2S NWs (0 0 1) crystal plane, only the Ag mode and B1g mode have Raman activity, which theoretical curves are displayed in Supplementary Fig. 7.

Supplementary Note 3
The entire linear polarization detection measurement system is shown in Supplementary Fig. 9. A modulated laser beam is changed into linearly polarized light through a Glan-Taylor prism (polarizer) and irradiate to the surface of the polarization-sensitive photodetector through the half-wave plate.  Fig. 15b) and 30 Hz (Supplementary Fig. 15c) are applied to gate, and the Ids corresponding to each frequency are extracted to obtain the frequency characteristic of the transistor shown in Supplementary Fig. 15d.
Experimental results explain the operating frequency of the transistor can reach 30 Hz under the premise of keeping Ids stable. In general, all the parameters of the transistor can meet the requirements of the integrated system.

Supplementary Note 5
The structure of ANN was shown in Fig. 4a Each image can be viewed as three parts. First part is body patterns, including six kinds of letters (B, D, I, J, O, T). The value of each pixel is randomly generated by MATLAB. The random algorithm is composed based on the formula 9 and formula 10 and the random angle range is between 178° and 198°. The second part is background signals, which are also generated by random algorithm based on the above formulas and the random angle range is between 88° and 108°. As the third part, noise signal is also generated by random algorithm based on the above formulas and the random angle range is between 108° and 178°. Finally, we get two image datasets, which belong to PSAS and Bi2Se2S based PS ( Supplementary Fig. 19). Supplementary Fig. 19a shows six types of images in two datasets. Supplementary Fig. 19b and c show images constructed according to the above method on the basis of six basic images, respectively. From Supplementary Fig. 19b and 19c, it can be seen that the image constructed by the PSAS, in which the background noise has little effect on the letter pattern. On the contrary, under the influence of background noise, the letters in the image constructed from PS shown in Supplementary Fig. 19b will be blurred a lot, which will cause the efficiency and accuracy of image recognition to decrease.