Guest Editorial Special Issue on Mid-Infrared Lasers and Applications

Mid-infrared （mid-IR） lasers, generally defined as having an operation wavelength in the spectral region of 2μm to 20μm, have attracted great scientific and technological interests owing to their widespread applications. This wavelength range not only contains some strong vibration transitions of many important molecules, thus, exhibiting enormous potential in medical, spectroscopy.

Review of a New IR Nonlinear Optical BaGa_4Se_7 Crystal

A newly grown Ba Ga4Se7 crystal has been synthesized via the Bridgman-Stockbarger technique.This new crystal has advantages of high nonlinear optics（NLO） coefficients,high laser damage thresholds,and wide transparent regions.The Ba Ga4Se7 crystal has bright application prospects as a nonlinear gain medium in mid-infrared and terahertz regions.In this paper,the crystalline structure and synthetic method of the Ba Ga4Se7 crystal are introduced.The refractive indices and absorption coefficients along three dielectric axes between 0.1 THz and 1.0 THz are also obtained.The terahertz difference frequency generation（THz-DFG） characteristics based on the BaG a4Se7 crystal in the frequency range of 0.1 THz to 1.0 THz are analyzed theoretically and the phase-matching conditions are calculated.The application of Ba Ga4Se7 crystals in terahertz wave generation is also discussed.

红外图像序列中不均匀背景消除新方法

从红外相机自身特性和使用角度两方面对靶场红外图像序列中不均匀(花纹)背景产生的原因进行了剖析,分析了传统红外图像非均匀校正算法在处理靶场序列红外图像上的优缺点,提出在目标跟踪过程中随着场景变化,基于实时线性标定的非线性红外图像的校正的新方法,克服了传统方法的弊端,实时确定了校正增益系数和校正因子,消除了序列红外图像中不均匀背景。通过对含有弱小目标的靶场实际序列红外图像进行仿真验证表明,新方法去除了图像固定图案噪声,消除了探测器坏元的影响,输出了理想的序列红外图像。

激光技术在主动红外对抗中的应用研究

主动红外对抗技术是光电对抗领域中的一个重要分支。本文根据红外制导导弹和红外热成像装备的工作原理,阐述了用激光来对其进行干扰的两种模式,给出了干扰激光能量的计算方法,并通过试验对之加以印证。试验结果表明:较低的激光能量对红外装备进行干扰能获得很好的干扰效果,低功率的战术激光器在主动红外对抗中有着广泛的应用前景。

采用可变增益观测器的红外导引头导气管扰动补偿

为了提高红外导引头的跟踪精度,降低导气管对导引头控制系统的影响,提出一种新型可变增益扰动观测器。首先,利用搭建的导引头实验系统研究了导气管干扰的扰动特性。然后,在分析导气管扰动的系统特性基础之上,结合经典扰动观测器理论,设计了新型可变增益扰动观测器,并分析了其鲁棒稳定性。最后,针对某实际红外导引头系统,设计了可变增益扰动观测器,并进行了导气管扰动抑制实验。结果表明:经典扰动观测器无法对导气管的扰动进行有效的抑制,而采用可变增益扰动观测器后,系统速度阶跃响应稳定精度提高71.1%;位置阶跃响应稳定精度提高42.8%。研究表明可变增益扰动观测器可以有效地抑制红外导引头中的导气管扰动。

黑硅材料在光电探测研究领域的前景及挑战

在详细介绍黑硅材料的形成机理,包括超过固溶度的S原子引起的高红外吸收基础上,介绍了黑硅材料在光电探测研究领域的应用,并指出黑硅光电探测器目前面临如何平衡退火消除缺陷及由此带来的红外吸收下降的问题,但黑硅探测器件的增益机制问题仍然不清楚,有待解决.

Emerging low-dimensional materials for mid-infrared detection

Mid-infrared(IR)detectors based on the emerging low-dimensional(two-dimensional and quasi one-dimensional)materials offer unique characteristics including large bandgap tunability,optical polarization sensitivity and integrability with typical silicon process,which are not available in the mid-IR detectors based on traditional compound semiconductors.Here,we review the recent progress in study of mid-IR detectors based on the low-dimensional materials,including black phosphorus,black arsenic phosphorus,tellurene and BaTiS3,from the perspectives of crystal structure,material synthesis,optical properties,and the detector characteristics.The detector gain and detectivity are benchmarked,and the unique properties,such as the polarization sensitivity,are discussed.We also provide our perspective about key future research directions in this field.

Scaling all-fiber mid-infrared supercontinuum up to 10 W-level based on thermal-spliced silica fiber and ZBLAN fiber

We demonstrate an integrated all-fiber mid-infrared(mid-IR)supercontinuum(SC)source generated by a 1.95μm master oscillator power amplifier system and a single-mode ZBLAN(ZrF_4–BaF_2–LaF_3–AlF_3–NaF)fiber.The maximum average output power is 10.67 W with spectral bandwidth covering from～1.9 to 4.1μm.The single-mode ZBLAN fiber and silica fiber are thermal-spliced to enhance the robustness and practicability of the system.It is,to the best of our knowledge,the first high-power integrated compacted all-fiber mid-IR SC source based on thermal-spliced silica fiber and ZBLAN fiber.

Broadband ultrafast nonlinear optical response of few-layers graphene: toward the mid-infrared regime

Gapless linear energy dispersion of graphene endows it with unique nonlinear optical properties, including broadband nonlinear absorption and giant nonlinear refractive index. Herein, we experimentally observed that fewlayers graphene has obvious nonlinear absorption and large nonlinear refraction, as investigated by the Z-scan technique in the mid-infrared（mid-IR） regime. Our study may not only, for the first time to our knowledge, verify the giant nonlinear refractive index of graphene(～10-7cm2∕W) at the mid-IR, which is 7 orders of magnitude larger than other conventional bulk materials, but also provide some new insights for graphene-based mid-IR photonics,potentially leading to the emergence of several new conceptual mid-IR optoelectronics devices.

Spatial Dynamics of Cropland and Cropping Pattern Change Analysis Using Landsat TM and IRS P6 LISS III Satellite Images with GIS

The study of the spatial patterns and temporal changes of cropland is important to understand the underlying factors and the functional effects of the agricultural landscape. On the other hand, crop dynamics mapping is essential to know the overall agro-spatial diversity of the area. Therefore, this paper addressed a spatio-temporal analysis of cropland and cropping pattern change in the Bogra district of Bangladesh over the last 16 years （between 1988/89 and 2004/05）. In this paper, crop mapping from multi-temporal and multi-sensor satellite images was described. Landsat TM and IRS P6 LlSS Ⅲ satellite images were used with GIS for spatial dynamics of cropland and cropping pattern change analysis. First, seasonal cropland maps were derived from object-based classification of satellite images, then two-date classified image differencing with GIS overlay technique and decision rules were applied. Cropping pattern change was analyzed in a spatial and quantitative way for the 16 years and for this, Integrated Land and Water Information System （ILWIS） and Land Change Modular （LCM） of IDRISl Andes were used. The results showed that in the area, mono crop cultivation was found in summer, but in winter, areas under different crop cultivation had changed dramatically. Change analysis showed that the changes mainly occurred in the north northwest and southwest of the areas, and during the time the highest change area was found under the rice-potato pattern.

A 6-7 GHz,40 dB receiver RF front-end with 4.5 dB minimum noise figure in 0.13μm CMOS for IR-UWB applications

A wideband receiver RP front-end for IR-UWB applications is implemented in 0.13μm CMOS technology. Thanks to the direct sub-sampling architecture,there is no mixing process.Both LNA and VGA work at RF frequencies.To optimize noise as well as linearity,a differential common-source LNA with capacitive cross- coupling is used,which only consumes current of 1.8 mA from a 1.2 V power supply.Following LNA,a two-stage current-steering VGA is adopted for gain tuning.To extend the overall bandwidth,a three-stage staggered peaking technique is used.Measurement results show that the proposed receiver front-end achieves a gain tuning range from 5 to 40 dB within 6-7 GHz,a minimum noise figure of 4.5 dB and a largest IIP_3 of-11 dBm.The core receiver (without test buffer) consumes 14 mW from a 1.2 V power supply and occupies 0.58 mm^2 area.

A Refractive Index Sensor Based on Four-Wave Mixing in D-Shaped Tellurite Photonic Crystal Fiber

In this study,we design a refractive index(RI)sensor using a novel cadmium telluride photonic crystal fiber(TPCF).Based on four-wave mixing(FWM),the changes in RI can be accurately detected,and RI sensing in the mid-infrared region(MIR)can be achieved by detecting wavelength shifts in the Stokes and anti-Stokes spectra caused by the changes in RI of the liquid to be measured.When the pump wavelength of FWM lies in the normal and abnormal dispersion regions of the TPCF,the RI response of the idler frequency wave and the signal wave are analyzed by numerical simulation methods.The simulation results show that the RI sensitivity of the sensor can be as high as 7692 nm/RIU with a linearity is up to 99.9%at the pump wavelength of 3380 nm.To our knowledge,the RI sensing sensitivity of the MIR is presented for the first time in this study by using FWM in the non-silicon PCF.

基于TMS320C6678的高动态范围红外图像细节增强算法改进与实现

利用图像分层处理的细节增强基本框架,提出了一种基于引导滤波器的高动态范围红外图像显示与细节增强算法。该算法能有效将高动态范围红外图像映射到适合监视器显示的动态范围,且能有效调整图像对比度,增强图像细节,抑制背景噪声。相比较于其他同类算法,该算法计算量少,易于工程实现,且不会产生梯度翻转效应。并研究设计了基于TMS320C6678DSP芯片的细节增强图像处理系统,实现了图像视频流的传输、处理等系列功能。实验结果表明了本算法的优势。

Tm^(3+)掺杂硫卤玻璃光纤的中红外增益特性研究

采用高温熔融淬冷法制备了1%Tm3+掺杂的72GeS2-18Ga2S3-10CsI(GGSI)硫卤玻璃,测试了样品的折射率、吸收光谱和800nm激光泵浦下的中红外荧光光谱,利用Judd-Ofelt和Futchbauer-Ladenburg(FL)理论分析计算了Tm3+在GGSI玻璃中的自发辐射几率、荧光分支比、辐射寿命、吸收截面、发射截面等光谱参数,进而建立了Tm3+的四能级粒子数速率-光功率传输方程模型,模拟计算Tm3+掺杂GGSI玻璃光纤中红外3.73μm波段的增益与掺杂光纤长度、泵浦功率和信号功率的关系。模拟结果显示,硫卤玻璃基掺铥光纤具有较高的信号增益和较宽的中红外增益谱,泵浦功率为1 000mW时,最大小信号增益值达到30dB,20dB增益带宽达到180nm,同时也存在合适的泵浦功率和光纤掺杂长度以期获得最佳信号增益。表明Tm3+掺GGSI硫卤玻璃光纤可作为中红外3.73μm波段放大的理想增益介质。