Physically Unclonable Holographic Encryption and Anticounterfeiting Based on the Light Propagation of Complex Medium and Fluorescent Labels.

Physically unclonable function (PUF) methods have high security, but their wide application is limited by complex encoding, large database, advanced external characterization equipment, and complicated comparative authentication. Therefore, we creatively propose the physically unclonable holographic encryption and anticounterfeiting based on the light propagation of complex medium and fluorescent labels. As far as we know, this is the first holographic encryption and anticounterfeiting method with a fluorescence physically unclonable property. The proposed method reduces the above requirements of traditional PUF methods and significantly reduces the cost. The angle-multiplexed PUF fluorescent label is the physical secret key. The information is encrypted as computer-generated holograms (CGH). Many physical parameters in the system are used as the parameter secret keys. The Diffie-Hellman key exchange algorithm is improved to transfer parameter secret keys. A variety of complex medium hologram generation methods are proposed and compared. The effectiveness, security, and robustness of the method are studied and analyzed. Finally, a graphical user interface (GUI) is designed for the convenience of users. The advantages of this method include lower PUF encoding complexity, effective reduction of the database size, lower requirements for characterization equipment, and direct use of decrypted information without complicated comparative authentication to reduce misjudgment. It is believed that the method proposed in this paper will pave the way for the popularization and application of PUF-based anticounterfeiting and encryption methods.

Chromaticity-Tunable All-Inorganic Color Converters Fabricated by 3D Printing for Modular Plant Growth Lighting Devices.

In photopolymerization-induced 3D printing of glass and ceramics, the demand for a slurry that has high photosensitivity, low viscosity, and high solid content leads to a limited selection of suspended particles. To this end, ultraviolet-assisted direct ink writing (UV-DIW) is proposed as a new 3D printing compatible approach. A curable UV ink is synthesized, which overcomes the material limitation. Benefiting from the advantage of the UV-DIW process, CaAlSiN3:Eu2+/BaMgAl10O17:Eu2+ phosphors in glass (CASN/BAM-PiG) as chromaticity-tunable specially shaped all-inorganic color converters are prepared for plant growth lighting using an optimized heat treatment procedure. Size compatible dome-type and flat-type CaAlSiN3:Eu2+ phosphors in glass (CASN-PiG) are constructed in batches. The manufactured dome-type PiG-based light-emitting diodes (LEDs) exhibit better heat dissipation capacity and a larger divergence angle. The advantage of CASN/BAM-PiG in plant growth lighting is confirmed by the high degree of resemblance between the emission spectra of CASN/BAM-PiG and the absorption spectra of carotenoid and chlorophyll. A series of dome-type CASN/BAM-PiG based LEDs with selective region doping are constructed, which can weaken reabsorption effects and scientifically match the requirements of different plants. The excellent color-tunable ability and high degree of spectral resemblance indicate the superiority of the proposed UV-DIW process in all-inorganic CASN/BAM-PiG color converters for intelligent agricultural lighting.

Non-uniform angular spectrum method in a complex medium based on iteration.

The traditional angular spectrum method has an inherent problem that the region of diffraction propagation should be homogeneous. However, in some cases, the medium of the diffraction propagation region is inhomogeneous. In this Letter, based on iteration we proposed the non-uniform angular spectrum method for diffraction propagation calculation in a complex medium. By phase pre-processing in the spatial domain and diffraction calculation in the spatial frequency domain, the diffraction propagation problem of the light field in a complex medium is solved. Theoretical formulation and numerical examples as well as experimental investigation are presented to confirm the validity of the proposed method. The advantages of this method include faster computation, smaller memory requirement, and the ability to compute a larger area compared with the finite element method as well as the ability to compute the non-paraxial case compared with the standard fast Fourier transform beam propagation method.

High-energy Q switched Yb-doped fiber laser based on a ternary layered structured Ti2AlC saturable absorber.

Ti2AlC is a kind of ternary layered structured ceramic metal compound, combining the advantages of both ceramic and metal. Herein, the saturable absorption performance of Ti2AlC at the 1-µm wave band is investigated. The Ti2AlC behaves with excellent saturable absorption, which has a modulation depth of 14.53% and a saturable intensity of 13.27 MW/cm2. An all-normal dispersion fiber laser based on the Ti2AlC saturable absorber (SA) is constructed. The repetition frequency of the Q switched pulses increased from 44 to 49 kHz as the pump power rose from 276 to 365 mW, and the corresponding pulse width decreased from 3.64 to 2.42 µs. The maximum output single Q switched pulse energy is as high as 169.8 nJ. Our experiments prove that the MAX phase Ti2AlC has potential as a low-cost, simple preparation, and broadband SA material. To the best of our knowledge, this is the first demonstration of Ti2AlC serving as a SA material achieving Q switched operation at the 1-µm wave band.