An Improved Temperature Compensation Method for Fiber Bragg Grating Pressure Sensor Based on Extreme Learning Machine

According to the problem of the sensor nonlinear changes occur at high temperatures, extreme learning machine model, is presented in this thesis the pressure sensitive grating and removing the temperature of the grating experiment data for training, establish a nonlinear model of wavelength, temperature, predict the experimental temperature, then the temperature data of pressure-sensitive grating the training set of training samples, the nonlinear model, temperature - wavelength prediction test set sample output wavelength, achieve the goal of improved temperature compensation method. The experimental results show that the algorithm can achieve a more ideal temperature compensation effect.

Inverse-designed ultra-compact high efficiency and low crosstalk optical interconnect based on waveguide crossing and wavelength demultiplexer

In this paper, we use the inverse design method to design an optical interconnection system composed of wavelength demultiplexer and the same direction waveguide crossing on silicon-on-insulator (SOI) platform. A 2.4 μm × 3.6 μm wavelength demultiplexer with an input wavelength of 1.3–1.6 μm is designed. When the target wavelength of the device is 1.4 μm, the insertion loss of the output port is − 0.93 dB, and there is − 18.4 dB crosstalk, in TE0 mode. The insertion loss of the target wavelength of 1.6 μm in TE0 mode is − 0.88 dB, and the crosstalk is − 19.1 dB. Then, we designed a same direction waveguide crossing, the footprint is only 2.4 μm × 3.6 μm, the insertion loss of the wavelength 1.4 μm and 1.6 μm in TE0 mode is − 0.99 dB and − 1 dB, and the crosstalk is − 12.14 dB and − 14.34 dB, respectively. Finally, an optical interconnect structure composed of two devices is used, which can become the most basic component of the optical interconnect network. In TE0 mode, the insertion loss of the output wavelength of 1.4 μm at the output port is − 1.3 dB, and the crosstalk is − 29.36 dB. The insertion loss of the output wavelength of 1.6 μm is − 1.39 dB, and the crosstalk is − 38.99 dB.

High-Efficiency Ho:YAP Pulse Laser Pumped at 1989 nm

A Tm:YAP laser with an output wavelength of 1989 nm was selected for the first time as the pump source of a Q-switched Ho:YAP laser. When the absorbed power was 30 W, an average power of 18.02 W with the pulse width of 104.2 ns acousto-optic (AO) Q-switched Ho:YAP laser was obtained at a repetition frequency of 10 kHz. The slope efficiency was 70.11%, and the optical-optical conversion efficiency was 43.03%. The output center wavelength was 2129.22 nm with the line width of 0.74 nm.

Switchable Multimode Microlaser based on AIE Microsphere

<p><a>Switchable multimode microlasers are of great significance to the development of photonic devices with high integration levels.</a> <a>Herein, we demonstrate an acid/alkaline gas responsive multimode AIEgen@starch microsphere-based microlaser. The aggregation-induced emission (AIE) active fluorescent dye ASCPI is used as the gain medium in this study. ASCPI was weakly emissive in water but became highly emissive when introduced to the starch microsphere as a guest molecule. The resultant ASCPI@starch microsphere worked well as a typical whispering-gallery-mode microlaser. The laser mode wavelengths were size dependent. Due to the sensitivity of ASCPI to pH, the output wavelength of the microlaser could be switched to shorter wavelength by acetic acid vapor treatment or longer wavelength by NH₃ vapor treatment. This work will provide a useful enlightenment for the rational design of effective switchable lasers using AIE materials with a simple preparation procedure.</a></p>

Switchable Multimode Microlaser based on AIE Microsphere

<p><a>Switchable multimode microlasers are of great significance to the development of photonic devices with high integration levels.</a> <a>Herein, we demonstrate an acid/alkaline gas responsive multimode AIEgen@starch microsphere-based microlaser. The aggregation-induced emission (AIE) active fluorescent dye ASCPI is used as the gain medium in this study. ASCPI was weakly emissive in water but became highly emissive when introduced to the starch microsphere as a guest molecule. The resultant ASCPI@starch microsphere worked well as a typical whispering-gallery-mode microlaser. The laser mode wavelengths were size dependent. Due to the sensitivity of ASCPI to pH, the output wavelength of the microlaser could be switched to shorter wavelength by acetic acid vapor treatment or longer wavelength by NH₃ vapor treatment. This work will provide a useful enlightenment for the rational design of effective switchable lasers using AIE materials with a simple preparation procedure.</a></p>

A Remote Sensor System Based on TDLAS Technique for Ammonia Leakage Monitoring

The development of an efficient, portable, real-time, and high-precision ammonia (NH3) remote sensor system is of great significance for environmental protection and citizens’ health. We developed a NH3 remote sensor system based on tunable diode laser absorption spectroscopy (TDLAS) technique to measure the NH3 leakage. In order to eliminate the interference of water vapor on NH3 detection, the wavelength-locked wavelength modulation spectroscopy technique was adopted to stabilize the output wavelength of the laser at 6612.7 cm−1, which significantly increased the sampling frequency of the sensor system. To solve the problem in that the light intensity received by the detector keeps changing, the 2f/1f signal processing technique was adopted. The practical application results proved that the 2f/1f signal processing technique had a satisfactory suppression effect on the signal fluctuation caused by distance changing. Using Allan deviation analysis, we determined the stability and limit of detection (LoD). The system could reach a LoD of 16.6 ppm·m at an average time of 2.8 s, and a LoD of 0.5 ppm·m at an optimum averaging time of 778.4 s. Finally, the measurement result of simulated ammonia leakage verified that the ammonia remote sensor system could meet the need for ammonia leakage detection in the industrial production process.

Molecular Design of d-Luciferin-Based Bioluminescence and 1,2-Dioxetane-Based Chemiluminescence Substrates for Altered Output Wavelength and Detecting Various Molecules

Optical imaging including fluorescence and luminescence is the most popular method for the in vivo imaging in mice. Luminescence imaging is considered to be superior to fluorescence imaging due to the lack of both autofluorescence and the scattering of excitation light. To date, various luciferin analogs and bioluminescence probes have been developed for deep tissue and molecular imaging. Recently, chemiluminescence probes have been developed based on a 1,2-dioxetane scaffold. In this review, the accumulated findings of numerous studies and the design strategies of bioluminescence and chemiluminescence imaging reagents are summarized.

A Fire Warning Method Using Tunable Diode Laser Absorption Spectroscopy

Tunable diode laser absorption spectroscopy (TDLAS) technology is adopted herein to detect fire gas produced in the early stage of the fire. Based on this technology, a fire warning detection system with multiple lasers and detectors is proposed. Multiple drivers input laser’s temperature and injected current data, making its output wavelength consistent with the measured gas’ absorption peak wavelengths in absorption spectroscopy. Multiple light beams are coupled to the same optical fiber. After the light beams pass through the long optical path absorption cell filled with fire gas, the beams are separated by a converter. The signals are demodulated by different detectors and further analyzed for fire warnings. After the fire warning system’s design, the system’s various hardware modules are designed, including the light source module, TDLAS controller, gas chamber module, photoelectric detector, and data collection. When the temperature remains unchanged, the output wavelength is linearly related to the injected current. When the injected current remains unchanged, the output wavelength is linearly related to the operating temperature. With a semiconductor laser’s injected current of 40 mA, the initial temperature of 38.6 °C, and the output wavelength of 1578.16 nm, the output wavelength increases continuously as the temperature increases. The harmonic signal amplitude after gas absorption is positively correlated with the measured gas concentration, indicating that the second harmonic signals can estimate the fire gas concentration.

Light source with variable wavelength based on acousto-optical deflector

The proposed work analyzes the design features of the acousto-optical deflector and filter on paratelurite. It is shown that under certain conditions the acousto-optical deflector can be used as an acousto-optical filter (as an element that performs spectral filtering of the incident light beam). The fundamental possibility of creating a monochromatic light source with a variable wavelength and a spectrum width of about 5 nm using an acousto-optical deflector as an element that adjusts the original wavelength is shown experimentally. As a broadband light source in this system, a semiconductor laser operating in subthreshold mode was used. The dependence of the output wavelength on the acoustic frequency is obtained. The comparison of experimental data with the calculated ones is given, it is shown that they have small differences.

Tunable Stokes Laser Based on KTiOPO4 Crystal

The characteristics of a tunable Stokes laser based on the cascaded stimulated polariton scattering and stimulated Raman scattering in KTiOPO4 crystal were studied experimentally and theoretically. When the pumping wavelength was 1064 nm, the Stokes laser output wavelength was able to be tuned discontinuously from 1112.08 nm to 1113.64 nm, from 1114.94 nm to 1115.77 nm, and from 1117.37 nm to 1119.92 nm, and the maximum output power appeared at 1118.86 nm. With a pulse repetition frequency of 7 kHz and a pump power of 6.0 W, the maximum output power of the Stokes laser reached 734 mW, and the corresponding diode to laser conversion efficiency was 12.2%. The rate equations describing the temporal evolutions of the fundamental and Stokes waves by noncollinear stimulated polariton scattering and the Stokes wave by collinear stimulated Raman scattering were derived. They were used to simulate the tunable Stokes laser. The calculated results were in agreement with the experimental results on the whole.