Lensless multiple-image optical encryption based on improved phase retrieval algorithm.

A novel architecture of the optical multiple-image encryption based on the modified Gerchberg-Saxton algorithm (MGSA) by using cascading phase only functions (POFs) in the Fresnel transform (FrT) domain is presented. This proposed method can greatly increase the capacity of the system by avoiding the crosstalk, completely, between the encrypted target images. Each present stage encrypted target image is encoded as to a complex function by using the MGSA with constraining the encrypted target image of the previous stage. Not only the wavelength and position parameters in the FrT domain can be keys to increase system security, the created POFs are also served mutually as the encryption keys to decrypt target image from present stage into next stage in the cascaded scheme. Compared with a prior method [Appl. Opt.48, 2686-2692 (2009)], the main advantages of this proposed encryption system is that it does not need any transformative lenses and this makes it very efficient and easy to implement optically. Simulation results show that this proposed encryption system can successfully achieve the multiple-image encryption via fewer POFs, which is more advantageous in simpler implementation and efficiency than a prior method where each decryption stage requires two POFs to accomplish this task.

Thickness for optimizing of organic layer and multi-layer anode on luminance efficiency in white-light top-emission organic light-emitting diodes.

The multilayer contact structures in both the anode and organic layers for top-emission organic light emitting diodes (TEOLEDs) are studied in this paper. The anode consists of aluminum/gold (Al/Au). The Al is used for high reflectivity and Au for high work function by enhancing the hole injection from the anode into the organic hole injection layer. The organic layer thicknesses on the luminance characteristics were studied. The hole injection (HIL), hole transport (HTL) and electron transport layer (ETL) thicknesses were adjusted to balance the electron and hole recombination ratio. A highest brightness and best luminance efficiency of 8041 cd/m2 and 3 cd/A were obtained, respectively. After optimization of each organic layer thickness, the white top-emission organic light emitting diodes (white TEOLEDs) was also studied. The white TEOLEDs were achieved using two approaches with doped concentrations adjustment (CIE coordinates at x = 0.31, y = 0.38, density of 0.6%) and doped positions adjustment with CIE coordinates at x = 0.30, y = 0.34 at position = 15 nm away from carriers recombination interface.

Black film for improving the contrast ratio of organic light emitting diodes.

This paper presents a black film with double period metal-organic cathode structure for reducing the cathode reflection and enhancing the contrast ratio (CR) in organic light emitting diodes (OLEDs). The absorption and destructive interference effect caused by the copper-phthalocyanine (CuPc) and ultra thin aluminum (Al) periodic layers decrease the ambient light. The double-period black film structure (Al/CuPc/Al/CuPc/Al) has the lowest reflected luminance of 2.61 cd/m2 during ambient light of 33.5 cd/m2. The device CR without any black film is only 82.5. The device with single period black film (Al/CuPc/Al) obtains up to 267.1 and the highest CR of 958 can be achieved with a double period black film Al/CuPc/Al/CuPc/Al structure.