Polarization holography has attracted much attention in recent research[
Chinese Optics Letters, Volume. 17, Issue 8, 082302(2019)
Design of an all-optical logic sequence generator based on polarization holographic gratings On the Cover
In this Letter, an all-optical logic sequence generator based on two different polarization holographic gratings has been proposed and demonstrated, which has one input port and four output ports. The polarization state of input light signal determines logic output signals. It can produce four kinds of logic sequence output signals: 1000, 0100, 0010, and 0001, corresponding to the input light signal of four different polarization states: the p-linear, s-linear, left-handed circular, and right-handed circular. The two polarization gratings have been fabricated, and the working principle of the logic sequence generator has been proved by diffraction pattern analysis of polarization gratings.
Polarization holography has attracted much attention in recent research[
In recent years, applications of optical communication devices in optical computing and other fields have found great progress[
In this Letter, we designed an all-optical logic sequence generator, which has one input port and four output ports, based on two different polarization holographic gratings. The logic signals of output ports depend entirely on the polarization of the input light signal. It can produce four kinds of logic sequence output signals: 1000, 0100, 0010, and 0001, corresponding to the input light signal of four different polarization states: the p-linear, s-linear, left-handed circular, and right-handed circular. There is no need for additional electronic control in this logic sequence generator, so it is very thin and can be easily integrated into various optical systems requiring optical signal control, such as optical path switching in an optical communication system.
Sign up for Chinese Optics Letters TOC Get the latest issue of Advanced Photonics delivered right to you!Sign up now
An all-optical logic sequence generator was designed, using a quarter-wave plate (QWP) of 633 nm and polarization holographic gratings DW1, DW2. The schematic diagram is shown in Fig.
Figure 1.Schematic of all-optical logic sequence generator. DW1 and DW2 are two different kinds of polarization holographic gratings. QWP is the quarter-wave plate. B1 and B2 represent the
In Fig.
Figure 2.(a) Diagram of the incident light signal of different polarization states and corresponding output light signals. (b) The logic sequence table. Column I1 represents four different polarizations of the incident light; columns O1, O2, O3, and O4 represent the diffraction light in four directions, respectively, corresponding to the yellow, green, blue, and red cylinders in Fig.
In Fig.
Figure 3.Diffraction patterns of (a) the DW1 grating and (b) the DW2 grating.
The DW1 grating was fabricated by orthogonal linearly polarized light interference. When the probe light is incident on polarization grating DW1, if the probe light is left-handed circularly polarized light, both the diffraction light of
The schematic diagram of working principle of the all-optical logic sequence generator is shown in Fig.
Figure 4.Schematic diagram of working principle of all-optical logic sequence generator.
Azo material is a kind of polarization sensitive material. If the pump light is linearly polarized, the azo molecules’ orientation will be perpendicular to the polarization direction of the pump light. Azo-doped liquid crystal polymer film is usually used to fabricate polarization gratings. Under the pump light, the photoisomerization of azo dyes occurs, and azo-doped liquid crystal polymer shows strong non-linear optical properties. In order to facilitate the fabrication of gratings, firstly, the real-time variation of its photoinduced birefringence was demonstrated by experiment. 532 nm laser was used as pumping light, and 633 nm laser was used as detecting light. The experimental optical path is shown in Fig.
Figure 5.Diagram of experimental optical path of photoinduced birefringence; P1 and P2 are two orthogonal polarizers.
In Fig.
Figure 6.Curves of the intensity variation of transmitted light versus the duration of pump light. The black curve represents the intensity variation of transmitted light when pumping light is 18 mW and the red curve represents that of 30 mW.
It can be seen that when the azo liquid crystal film is not illuminated by pumping light, the lock-in amplifier does not detect any transmitted light intensity signal, indicating that the azo material does not have birefringence characteristics at this time. When the pump light is turned on, the intensity of light detected by the lock-in amplifier increases continuously, indicating that under the action of pump light, the birefringence of azo liquid crystal material increases continuously. The intensity of transmitted light maintains its stability after reaching a maximum. When pump light is turned off, the intensity of transmitted light decreases slightly and tends to be stable, which indicates that the photoinduced birefringence of azo liquid crystal polymer material is relatively stable. Gratings DW1 and DW2 were fabricated by polarization holographic interference, respectively. Figures
Figure 7.Schematic of the optical path for writing polarization gratings (a) DW1 and (b) DW2. BS, beam splitter; M1, M2, M3, mirror; HWP, half-wave plate; QWP, quarter-wave plate.
In Fig.
Figure 8.(a) Diffraction of DW1 grating. (b) Diffraction of DW2 grating. S, P, Left, and Right represent four kinds of incident light, respectively. The three red dots from left to right in each row represent the
The 633 nm laser was used as the probe light. In Fig.
Figure 9.Polarization states of incident light and diffraction light of DW1 and DW2. s-linearly polarized incident light and
The above experiment results can be demonstrated by the Jones matrix. As for DW1, the expressions of the polarization of 532 nm orthogonal linearly polarized light are
The diagram of the polarization modulation of the interferential light field in the material film is shown in Fig.
Figure 10.Schematic diagram of polarization modulation in orthogonal linearly polarized light interference field.
It is easy to obtain the
When the probe light is linearly polarized, the polarization states of
When the probe light is circularly polarized, the light field of the
When the detecting light is left-handed circularly polarized,
As for DW2, expressions of 532 nm orthogonal circularly polarized light are
The diagram of the polarization modulation of the interferential light field in the material film is shown in Fig.
Figure 11.Schematic diagram of polarization modulation in orthogonal circularly polarized light interference field.
It is easy to obtain the
When the probe is linearly polarized, the light field of the
Whether the detecting light is s-linearly polarized or p-linearly polarized, the diffraction light is the same. When the probe light is circularly polarized, the light field of the
If the detecting light is left-handed circularly polarized,
In summary, an all-optical logic sequence generator based on two different polarization holographic gratings was proposed. The logic sequence generator can produce four different logic sequence signals by controlling the polarization state of the input signal light. In order to demonstrate the function of this device, the two polarization gratings were fabricated. Before fabrication of the gratings, the experiment of real-time variation of photoinduced birefringence of azo liquid crystal polymer materials was carried out. Furthermore, gratings DW1 and DW2 were fabricated by orthogonal linearly polarized light interference and orthogonal circularly polarized light interference, respectively. Their diffraction patterns and polarization states were proved by the Jones matrix theory. In order to reach the theoretical maximum value of diffraction efficiency, the thickness of the film needs to be precisely controlled to meet the half-wave condition. Because no additional electrical control is required, the device can be very thin and easily integrated into many optical communication systems requiring optical signal control, such as optical path switching in optical communication systems.
[1] P. Cai, J. Wang, C. Wang, P. Zeng, H. Li. Chin. Opt. Lett., 14(2016).
[14] N. V. Tabiryan, S. R. Nersisyan, D. M. Steeves, B. R. Kimball. Opt. Photon. News, 21, 40(2010).
[16] L. Wu, X. R. Wang, C. D. Xiong, Z. Q. Huang, R. S. Zhuo, J. R. Rao, Q. G. Tan. Chin. Opt. Lett., 15(2017).
[17] Z. Han, C. Sun, X. Jin, H. Jiang, C. Yao, S. Zhang, W. Liu, T. Geng, F. Peng, W. Sun, L. Yuan. Chin. Opt. Lett., 16(2018).
Get Citation
Copy Citation Text
Renjie Xia, Changshun Wang, Tianyu Chen, Yujia Pan, Ziyao Lü, Lili Sun. Design of an all-optical logic sequence generator based on polarization holographic gratings[J]. Chinese Optics Letters, 2019, 17(8): 082302
Category: Optical devices
Received: Feb. 13, 2019
Accepted: May. 17, 2019
Posted: May. 22, 2019
Published Online: Jul. 16, 2019
The Author Email: Changshun Wang (cswang@sjtu.edu.cn)