Controlled LED Lighting for Horticulture: A Review

As energy gradually becomes a more valuable commodity, the desire for reduced energy losses strengthens. Lighting is a critical field on this matter, as it accounts for a large percentage of the global electricity consumption and modern lighting systems are greatly more efficient than incandescent, discharge, and fluorescent lights. Previous research has proven that plants do not require the entire visible spectrum but react only to specific wavelengths, making it possible to control their growth and yield via artificial lighting. The flexibility of control of Light Emitting Diode (LED) lights allows for the combination of great energy losses reduction and controlled plant growth, achieving the improvement of two major parameters in a single action. This review paper summarizes the current research on the effect different light wavelengths have on specific plant species and discusses the applications of LED lighting for horticulture, yield storage, and disease protection.

Impact of the self-steepening effect on soliton spectral tunneling in PCF with three zero dispersion wavelengths

This work presents a numerical investigation of the self-steepening（SS） effect on the soliton spectral tunneling（SST） effect in a photonic crystal fiber（PCF） with three zero dispersion wavelengths. Interestingly, the spectral range and flatness can be flexibly tuned by adjusting the SS value. When the SS coefficient increases, the energy between solitons and dispersion waves is redistributed, and the red-shifted soliton forms earlier in the region of long wavelength anomalous dispersion. As a consequence, the SST becomes more obvious. The findings of this work provide interesting insights in regard to the impact of the SST effect on tailored supercontinuum generation.

Spectral reflectance response to nitrogen fertilization in field grown corn

This study was carried out to analyze the spectral reflectance response of different nitrogen levels for corn crops.Four different nitrogen treatments of 0%,80%,100%and 120%BMP(best management practice)were studied.Principal component analysis-loading(PCA-loading)was used to identify the effective wavelengths.Partial least squares(PLS)and multiple linear regression(MLR)models were built to predict different nitrogen values.Vegetation indices(VIs)were calculated and then used to build more prediction models.Both full and selected wavelengths-based models showed similar prediction trends.The overall PLS model obtained the coefficient of determination(R^(2))of 0.6535 with a root mean square error(RMSE)of 0.2681 in the prediction set.The selected wavelengths for overall MLR model obtained the R^(2) of 0.6735 and RMSE of 0.3457 in the prediction set.The results showed that the wavelengths in visible and near infrared region(350-1000 nm)performed better than the two either spectral regions(1001-1350/1425-1800 nm and 2000-2400 nm).For each data set,the wavelengths around 555 nm and 730 nm were identified to be the most important to predict nitrogen rates.The vogelmann red edge index 2(VOG 2)performed the best among all VIs.It demonstrated that spectral reflectance has the potential to be used for analyzing nitrogen response in corn.

Design and fabrication of wavelength tunable AWGs based on the thermo-optic effect

In this Letter, a 16 channel 200 GHz wavelength tunable arrayed waveguide grating（AWG） is designed and fabricated based on the silicon on insulator platform. Considering that the performance of the AWG, such as central wavelength and crosstalk, is sensitive to the dimension variation of waveguides, the error analysis of the AWG with width fluctuations is worked out using the transfer function method. A heater is designed to realize the wavelength tunability of the AWG based on the thermo-optic effect of silicon. The measured results show that the insertion loss of the AWG is about 6 d B, and the crosstalk is 7.5 d B. The wavelength tunability of 1.1 nm is achieved at 276 m W power consumption, and more wavelength shifts will gain at larger power consumption.