Information encryption technique has broad applications in individual privacy, military confidentiality, and national security, but traditional electronic encryption approaches are increasingly unable to satisfy the demands of strong safety and large bandwidth of high-speed data transmission over network. Optical encryption technology could be more flexible and effective in parallel programming and multiple degree-of-freedom data transmitting application. Here, we show a dual-layer optical encryption fluorescent polymer waveguide chip based on optical pulse-code modulation technique. Fluorescent oligomers were doped into epoxy cross-linking SU-8 polymer as a gain medium. Through modifying both the external pumping wavelength and operating frequency of the pulse-code modulation, the sender could ensure the transmission of vital information is secure. If the plaintext transmission is eavesdropped, the external pumping light will be switched, and the receiver will get warning commands of ciphertext information in the standby network. This technique is suitable for high-integration and high-scalability optical information encryption communications.

Mode-division multiplexing (MDM) is a new method of space-division multiplexing (SDM) that can break through the limitation of single-mode transmission capacity and greatly improve the capacity of optical fiber communication. In the case of a few-mode (FM) system, it is possible that each mode can carry its own data steam and transmit long distances owing to a few-mode erbium-doped fiber amplifier (FM-EDFA). In addition, an Er ³⁺ -Yb ³⁺ co-doped waveguide amplifier (EYCDWA) based on polymer materials has numerous advantages of miniaturization and flexibility in planar integrated optics compared with the EDFA. This study explored the theory of a few-mode Er ³⁺ -Yb ³⁺ co-doped waveguide amplifier (FM-EYCDWA) and established a theoretical model of an FM-EYCDWA with a novel modified overlap integral factor. The differential modal gain (DMG) of the FM-EYCDWA can be reduced or even eliminated by equalizing the modified overlap integral factor of each signal mode. An unprecedented doping configuration adapted to the fabrication process of an optical waveguide was proposed to fill the gap between modal gains, which can be optimized by a genetic algorithm (GA). We investigated two optimization cases of three-mode and five-mode group FM-EYCDWAs to verify the validity of the theoretical model; both cases were optimized to minimize the DMGs under the same limitations, and excellent performance was presented, which demonstrated that the design method of the few-mode amplifiers we presented can offer a referable guideline.

In this work, we successfully developed a fluorinated cross-linked polymer Bragg waveguide grating-based optical biosensor to detect effective drug concentrations of ginkgolide A for the inhibition of pulmonary microvascular endothelial cell (PMVEC) apoptosis. Fluorinated photosensitive polymer SU-8 (FSU-8) as the sensing core layer and polymethyl methacrylate (PMMA) as the sensing window cladding were synthesized. The effective drug concentration range (5–10 µg/mL) of ginkgolide A for inhibition of PMVEC apoptosis was analyzed and obtained by pharmacological studies. The structure of the device was optimized to be designed and fabricated by direct UV writing technology. The properties of the biosensor were simulated with various refractive indices of different drug concentrations. The actual sensitivity of the biosensor was measured as 1606.2 nm/RIU. The resolution and detection limit were characterized as 0.05 nm and 3 × 10⁻⁵ RIU, respectively. The technique is suitable for safe and accurate detection of effective organic drug dosages of Chinese herbal ingredients.

In this work, a photonic device integration platform capable of integration of active-passive InP-based photonic devices without the use of material regrowth is introduced. The platform makes use of an adiabatic active-layer waveguide connection (ALWC) to move an optical beam between active and passive devices. The performance of this platform is analyzed using an example made up of four main sections: (1) a fiber coupling section for enabling vertical beam coupling from optical fiber into the photonic chip using a mode-matched surface grating with apodized duty cycles; (2) a transparent waveguide section for realizing passive photonic devices; (3) an adiabatic mode connection structure for moving the optical beam between passive and active device sections; and (4) an active device section for realizing active photonic devices. It is shown that the coupled surface grating, when added with a bottom gold reflector, can achieve a high chip-to-fiber coupling efficiency (CE) of 88.3% at 1550 nm. The adiabatic active-layer mode connection structure has an optical loss of lower than 1% (CE > 99%). The active device section can achieve an optical gain of 20 dB/mm with the use of only 3 quantum wells. The optimized structural parameters of the entire waveguide module are analyzed and discussed.