Fig.1 exhibits the excitation and emission spectra of 70ZnO-10P2O5-20SiO2:0.1Mn2+ glass. As we can see in Fig.1(a), when the monitoring peak is at 607 nm, the excitation peak of 70ZnO-10P2O5-20SiO2:0.1Mn2+ glass is around 254nm. In addition, PL spectra of 70ZnO-10P2O5-20SiO2:0.1Mn2+ glass is shown in the Fig.1(b), under 254 nm ultraviolet light irradiation, 70ZnO-10P2O5-20SiO2:0.1Mn2+ glass emits bright red luminescence. The emission shows a wide band and concentrates at 607 nm. These results suggest that the broad band emission near 607nm is originated from 4T1(4G)→6A1g(6S) of Mn2+ [15,16], so we can see bright red fluorescence. Meanwhile, the color of luminescence depends on the coordination environment of Mn2+ in the crystal lattice. When Mn2+ exists in the crystal lattice with four coordination (CN=4), the luminescence color is green; when CN=6, it’s red [17,18]. From this, we can judge that Mn2+ exists in the form of six coordination in 70ZnO-10P2O5-20SiO2:0.1Mn2+ optical storage material.
Fig.2 exhibits the LPL emission spectra of 70ZnO-10P2O5-20SiO2:0.1Mn2+ glass. Apart from PL phenomenon, we can also observe the obvious red LPL phenomenon of 70ZnO-10P2O5-20SiO2:0.1Mn2+ glass after 254 nm ultraviolet light irradiation. Fig.2(a) shows the LPL spectra of 70ZnO-10P2O5-20SiO2:0.1Mn2+ glass is same as the PL spectra, which the main peak values all located at 607 nm. Combined with the analysis of fluorescence spectrum, the emission of PL and LPL are all originated from 4T1(4G)→6A1g(6S) of Mn2+. From Fig.2(b), it can be seen that the LPL exhibits two processes of initial fast decay and subsequent slow decay. From this we can get the attenuation of the signal light when the material is reading out. Different from other rare earth doped ions, Mn2+doped 70ZnO-10P2O5-20SiO2 glass has suitable trap depths and laid the foundation for LPL and PSL. The long persistence luminescence intensity attenuation can be described by the following equation:
I=A1 exp(-x/t1)+ A2 exp(-x/t2)+y0
All data are in the second order exponential curve graph of the afterglow attenuation spectrum and the fitted correlation coefficient is 99.64%. The total decay lifetimes can be described by the following formula: 
t=( A1t12 + A1t22)/( A1t1 + A1t2)
from this, we can know the average decay lifetimes is 66.39s.
Fig.3 exhibits the PSL emission spectrum of 70ZnO-10P2O5-20SiO2:0.1Mn2+ glass. After pre-irradiating with 254 nm ultraviolet light for 10 minutes and wait until the afterglow is disappeared, re-exciting with 980 nm infrared light can obtain the red PSL phenomenon. Combined with fluorescence spectrum analysis, the emission of LPL and PSL originated from 4T1(4G)→6A1g(6S) of Mn2+. However, PSL phenomenon cannot be obtained in 70ZnO-10P2O5-20SiO2:0.1Mn2+ glass if without pre-irradiating with 254 nm ultraviolet light for 10 minutes. This indicates that 980nm re-excited 70ZnO-10P2O5-20SiO2:0.1Mn2+ glass luminescence originated from the energy stored in deep trap levels rather than up-conversion luminescence. Besides, the PSL and LPL phenomenon can’t be observed in 70ZnO-10P2O5-20SiO2 glass, which indicates that Mn2+ ions serve as glowing centers in PSL and LPL phenomenon. As we all know that LPL and PSL property are related to doped ions and trap depth. Doped ions determine the luminescence colour, the trap depth determines whether the photo-stimulated luminescence phenomenon can be observed. In this work, since the luminescence centers are all Mn2+ ions, the spectra of LPL and PSL are the same. The difference is that LPL and PSL are derived from different trap energy levels in 70ZnO-10P2O5-20SiO2:0.1Mn2+ glass. PSL decay also exhibits two processes of initial fast decay and subsequent slow decay. Compared with LPL decay, the electron transition process is similar to the emission process, but the intensity of the excitation energy and the source of the released electrons are different. In this work, the emission of LPL and PSL are all originated from 4T1(4G)→6A1g(6S) of Mn2+ and the attenuation curves of LPL and PSL are similar. Due to the unique advantages of glass, the 70ZnO-10P2O5-20SiO2:0.1Mn2+ glass is a high-security level optical information storage medium.
Fig.4 shows the relationship of Mn2+ contents and relative Intensity of 70ZnO-10P2O5-20SiO2:xMn2+ (x=0.1, 0.2, 0.3, 0.5, 1) glass. The spectra show that the luminescence intensity decrease as the Mn2+ contents increase. When the Mn2+ doping content reaches 1 mol%, LPL and PSL disappear due to the concentration quenching. With the increase of Mn2+ content, its distribution tends to be dense. Due to the same energy level structure between adjacent Mn2+, the outer electron orbits will connect to form an electronic bridge. This electronic bridge makes the motion interval of the excited electrons of adjacent Mn2+ emission center overlap, and the electrons move back and forth between the two emission centers. Even if there are oxygen vacancies with a suitable depth around, electrons will not fall into them with a high probability (that is, concentration quenching occurs), so that the charge density trapped by the traps decreases.
At present, we usually use TL spectroscopy to gain insight into internal defect structure of electron trapping optical storage materials. In order to understand the trap properties of 70ZnO-10P2O5-20SiO2:0.1Mn2+ glass such as trap depth and trap density, TL curves of the glass are measured and shown in Fig.5(a). The TL curve of 70ZnO-10P2O5-20SiO2:0.1Mn2+ shows a wide band from 300K to 600K, so we can see obvious LPL phenomenon and PSL phenomenon. As shown in the Fig.5(b), the TL curves were concentrated at 454K after Gaussian fitting. The TL curve of 70ZnO-10P2O5-20SiO2:0.1Mn2+ shows a wide band with a concentration at 454 K, from this we can assess the depth of the electronic trap. We can get the depth of the electronic trap by the following formula: 
Where, Tm is the Thermo-luminescence peak. The activation energy is 0.908eV for the result of 70ZnO-10P2O5-20SiO2:0.1Mn2+ glass. Electron trapping materials with stable optical properties require the matrix to have concentrated distribution of high-concentration deep trap energy levels (trap energy level depth>0.8eV) . In fact, PSL is suitable for deep traps because deep traps can permanently fix the carriers. In this work, the emission of LPL and PSL are all originated from 4T1(4G)→6A1g(6S) of Mn2+ and the spectrum of LPL and PSL are similar. The difference is that the intensity of the excitation energy and the source of the released electrons are different. It shows that under 980 nm infrared light and high temperature heat stimulation, the intensity of TL curve of deep traps is significantly reduced.
After irradiating 254 nm ultraviolet light through the photomask, the specific information pattern is stored in colorless transparent glass, and there is almost no afterglow after the sample is placed 12 hours at room temperature. When the colorless transparent glass was heated to 180°C, as shown in the Fig.6, the image “NJUPT” and the horse pattern are clearly displayed in the dark. Information can be written and read in colorless transparent glass due to the thermal stability and high transparency of the glass, which means that not only the service life can be greatly increased, but also the data security can be improved by changing the laser focus depth. Similarly, 980 nm infrared light can be used to read the information in the colorless transparent glass. Experiments show that after 24 hours of irradiating with 254 nm ultraviolet light, the red bright spot can be still observed by irradiating the colorless transparent glass with 980nm infrared light. If the area illuminated by high-energy photons is defined as“1”in the binary information and the area not illuminated by high-energy photons is defined as“0”in the binary information, the storage of digital information can be recorded. Different from high temperature heat stimulation, the readout of optical information under 980 nm infrared light stimulation provides a remote control method, which suggested a different application for future optical information storage.
In order to explore the PSL and LPL phenomenon mechanism, we put forward the possible explanations. According to TL analysis, 70ZnO-10P2O5-20SiO2: Mn2+ glass samples have a wide continuous trap depth distribution from 300K to 600K. The TL peak of Mn2+ doped 70ZnO-10P2O5-20SiO2 glass samples was 454 K (trap depth was 0.908eV). As we can see in the Fig.7, After irradiating 254 nm ultraviolet light, the electrons located at Mn2+ 4T1 (4G) will be excited to a higher excited state of 6A1g (6S), so we can see bright red PL. Mn2+doped 70ZnO-10P2O5-20SiO2 glass has suitable trap depths and laid the foundation for LPL and PSL. After pre-irradiating with 254 nm ultraviolet light for 10 minutes, electrons can be captured by different trap levels and we can see obviously LPL and LPL exhibits two processes of initial fast decay and subsequent slow decay. LPL is suitable for shallow traps because shallow traps cannot permanently fix the carriers. By applying external 980 nm light stimulation, electrons captured by deep trap levels re-excited and recombine with the luminescence center Mn2+ to emit light. In this work, the emission of LPL and PSL are all originated from 4T1(4G)→6A1g(6S) of Mn2+.