绝对辐射计一次反射不等效的影响及实验分析

为了提高星载光辐射测量精度,满足在轨测量数据向世界辐射参考标准溯源的需求,运用有限元单元法对太阳辐照度绝对辐射计(SIAR)的光电不等效性进行修正。SIAR采用典型的正圆锥腔结构及加热丝直接埋入银锥腔工艺,其光电不等效性源于激光加热照射时一次反射引起的偏差。针对该偏差定量修正难度较大的特点,结合SIAR腔组件的实际结构,建立与实验测量结果最大相对误差仅为0.86%的有限元体系,并运用该体系对SIAR的光电不等效性进行定量修正。修正结果表明,光束的一次反射引起了激光加热和电加热阶段的不同功率分布,其光电不等效性因子为1.0000589,不确定度为3.4×10-6。运用该因子对测量数据进行修正,得到SIAR的太阳总辐照度实际测量结果为(1365.70±1.24)W/m2。该修正完善了绝对辐射计的修正体系。     

4 K低温辐射计的吸收腔吸收率测试技术研究

为了实现低温辐射计工作温度4 K条件下吸收腔吸收率的测量,研究了变温条件下吸收腔吸收率的测量方法。通过在低温辐射计布儒斯特窗口前设计反射监测组件,并控制低温辐射计工作在10?6 Pa的真空环境下,调节低温辐射计制冷温度,分别测量室温条件和不同温度条件下低温辐射计吸收腔在632.8 nm处的反射信号,结合利用传统积分球法在室温条件下低温辐射计吸收腔632.8 nm处反射率的测量结果,通过计算可精确得到不同温度条件下低温辐射计吸收腔的吸收率。实验测量吸收腔在室温条件和4 K温度条件下的吸收率,分别为0.99976和0.99971,对4 K条件下低温辐射计吸收腔吸收率的测量不确定度进行评定,得到的结果显示其相对扩展不确定度为0.005%（k=2）。     

温度箱入射窗方案与温度场模拟

介绍了夜视仪可靠性试验中温度应力试验箱入射窗的结构方案,并通过其上的加热器加热避免低温造成内层窗口玻璃结霜,且确保光通道中温度梯度尽量均匀,计算加热器所需功率,并使用ANSYS软件对温度场进行模拟。     

MOCVD片式红外辐射系统调节曲线的仿真与分析

以片式红外加热的MOCVD反应室为研究对象,应用二位数学模型进行了有限元分析和计算,具体研究了加热器调节的依据--调节曲线的峰值变化情况。通过计算表明,片式加热器加热系统在石墨盘上的调节曲线峰值变化与加热器的加热功率、水平位置和大小有很密切的关系,文中解释了峰值移动的内在原因。得出设计加热器一些原则:加热器越多调节越灵活;外圈加热器最大加热功率要大于内圈加热器;最外圈加热器宜小。研究结果对MOCVD反应室加热系统设计以及在实际生产中的加热条件优化提供了参考。     

金黑在电校准热电辐射计中的应用

探测器表面涂有金黑的电校准热电辐射计广泛应用于对辐射功率的绝对测量。电校准热电辐射计是以热电探测器为基础研制的,同时又采用了光学调制和零位平衡技术,它对辐射功率进行绝对测量的基础是用经过调制的辐射功率和电功率交替加热覆有黑涂层和加热体的热电探测器,并使黑涂层所吸收的辐射功率与加热体产生的电功率相互等效,这样就直接将辐射功率测量转变为电功率测量了,而电功率的测量易于获得很高的精度,于是只要测量电功率,就实现了对辐射功率的准     

Nd:GdYVO4与Nd:YVO4的激光特性比较

在相同的实验条件下,分别采用平平直腔和V型折叠腔对比了Nd:GdYVO4和Nd:YVO4两种晶体的基频和腔内倍频特性.采用平平直腔在抽运功率为10.64 W时分别获得了5.35 W、6.29 W的1.06 μm基频输出,光-光转换效率达50.3%、59.1%,斜效率达58.1%、68.8%;采用V型折叠腔KTP腔内倍频,在抽运功率为6.71 W时分别获得了1.73 W和2.34 W的稳定倍频绿光输出,光-光转换效率达25.8%、34.9%.比较得出,Nd:GdYVO4-KTP绿光激光器的平均输出功率及稳定性均低于Nd:YVO4-KTP绿光激光器.     

基于加热器图案化LCD低温加热研究

为了改善机载液晶显示器低温加热不均匀问题,提出了一种均匀加热的方法.首先,用COMSOL软件建立加热器模型和进行热仿真,得到了加热的功耗和温度分布图.接着做加热器低温加热实验,实验测量了温度值校正仿真模型边界的热对流系数,根据需求优化仿真加热器,设计了一种边缘温度高于中心区域的加热器,并根据仿真用等效占空比方式制作样品...     

基于二维碲烯的太赫兹光电探测器

制备了金属-碲烯-金属的太赫兹光电探测器,实现了毫米波-太赫兹波下的光探测。结果表明,基于对数天线碲烯的太赫兹光电探测器在零偏压下具有较高的光响应率（40 mA /W,0.12 THz）,响应时间为8 μs,噪声等效功率（NEP）为4 pW·Hz^-0.5。研究结果为高性能室温太赫兹光探测提供了一种新的发展路径。     

部分端面抽运的Nd∶YVO_4板条固体激光器

利用自制高功率激光二极管(LD)列阵堆和波导整形抽运耦合系统,将抽运光耦合至Nd∶YVO4板条晶体,平平腔运转得到了1.064μm的偏振激光输出。在最大抽运功率为84 W时,透过率为10%的输出腔镜得到了31 W的激光功率输出,光-光效率37%,斜效率45%,板条晶体两个方向的输出光束质量差别较大。为了进一步提高光束质量,使用柱面镜混合腔结构,在最大抽运功率为86 W时,得到了19.3 W的1064 nm激光输出,测得的非稳腔和稳腔两个方向的M2因子分别为1.4和1.7。     

基于低温辐射计的红外辐射定标方法

在比较国际上基于低温辐射计的红外辐射定标技术的基础上,提出了以红外光源结合单色仪为辐射源,及以腔式热电堆探测器和低温辐射计为标准探测器的红外辐射定标方案.介绍了其结构和工作原理并给出了初步的定标结果.     

Temperature distribution in semiconductor wafers heated in ahot-wall-type rapid diffusion furnace

Transient temperature distribution was calculated for wafers heated in a new hot-wall-type rapid diffusion furnace. Two-dimensional radiative heat transfer was combined with unsteady conduction in wafers and the furnace. The furnace is composed of parallel plate heaters, and heats wafers to a temperature of about 1000°C. The heaters are divided into four zones and their heating powers are PID-controlled. Two wafers on a holder are inserted vertically from the bottom of the furnace, and heated for three minutes. The calculated results show the wafer temperature approached the desired heating temperature about one minute after insertion, agreeing with experimental results. The average temperature distribution in the wafers during heating is found to be within ±1°C at 1000°C, when the heating power (temperature) of the four zones is properly controlled. The effects of heater temperature, insertion speed, and holder thickness on the temperature distribution in wafers were calculated. The new hot-wall-type rapid diffusion furnace can be used to manufacture future VLSI     

Integrated thin film heater-thermocouple systems

A novel system of integrated thin-film heater with an embedded thermocouple was developed. Thin-film metallic heaters are widely used today in various fields of electronics and microelectronics applications. The main goal of the heater is usually to maintain the temperature in the heated zone. A deterministic method to manufacture an in situ heater––thermocouple system, with a pre-determined heater resistance, to give a required heat power, was developed. In order to examine this novel method, thin-film heaters were made using layers of Al and NiCr alloys. The temperature of the thin-film heater was measured while heating by an embedded thin-film thermocouple, positioned in the vicinity of the heater. This thin-film thermocouple system consisted of Ni–Ag alloy. A precise control of the growing heater film, while deposition, became possible using a simultaneous measurement of the heater sample resistance.     

Joule Heating Characteristics of Emulsion‐Templated Graphene Aerogels

The Joule heating properties of an ultralight nanocarbon aerogel are investigated with a view to potential applications as energy‐efficient, local gas heater, and other systems. Thermally reduced graphene oxide (rGO) aerogels (10 mg cm^?3) with defined shape are produced via emulsion‐templating. Relevant material properties, including thermal conductivity, electrical conductivity and porosity, are assessed. Repeatable Joule heating up to 200 °C at comparatively low voltages (≈1 V) and electrical power inputs (≈2.5 W cm^?3) is demonstrated. The steady‐state core and surface temperatures are measured, analyzed and compared to analogous two‐dimensional nanocarbon film heaters. The assessment of temperature uniformity suggests that heat losses are dominated by conductive and convective heat dissipation at the temperature range studied. The radial temperature gradient of an uninsulated, Joule‐heated sample is analyzed to estimate the aerogel's thermal conductivity (around 0.4 W m^?1 K^?1). Fast initial Joule heating kinetics and cooling rates (up to 10 K s^?1) are exploited for rapid and repeatable temperature cycling, important for potential applications as local gas heaters, in catalysis, and for regenerable of solid adsorbents. These principles may be relevant to wide range of nanocarbon networks and applications.     

基于低温辐射计高精度光辐射定标结果(1999和2003年)的对比研究

对1999年和2003年采用不同测量光路情况下可见光波段低温辐射计高精度光辐射定标测量结果及其不确定度进行了比较。结果表明,2003年低温辐射计激光功率测量不确定度比1999年的要小;2003年硅陷阱探测器光谱响应率测量不确定度和1999年的在同一水平上;陷阱探测器绝对光谱响应率变化在1．20%以内。这些结果证实陷阱探测器稳定性优良,光路改造合理。     

低温绝对辐射计不同定标光路的比对实验

低温辐射计是当前光辐射功率计量的最高标准,其测量精度的评价可以通过不同低温辐射计之间的比对来完成。开展了不同定标光路的低温辐射计比对实验。实验采用中国科学院安徽光学精密机械研究所研制的陷阱探测器作为传递标准,在633 nm波段对传递探测器的光谱响应度进行了绝对标定。比对结果表明,传递探测器的绝对光谱响应度的测量一致性为3.610-3,定标总合成不确定度为3.310-4(k=1),实验结果验证了两家单位低温绝对辐射计定标系统的可靠性和高精度。     

Modeling of circuits with strongly temperature dependent thermal conductivities for cryogenic CMOS

When designing and studying circuits operating at cryogenic temperatures understanding local heating within the circuits is critical due to the temperature dependence of transistor and noise behavior. Local heating effects of a CMOS ring oscillator and current comparator were investigated at T=4.2 K. In two cases, the temperature near the circuit was measured with an integrated thermometer. A lumped element equivalent electrical circuit SPICE model that accounts for the strongly temperature dependent thermal conductivities and special 4.2 K heat sinking considerations was developed. The temperature dependence on power is solved numerically with a SPICE package, and the results are typically within 3σ of the measured values for local heating ranging from to over 100 K.     

Fundamental limits for linearity of CATV lasers

We have considered nonlinear distortions in a subcarrier multiplexed optical transmission system arising from carrier heating effects in the source laser. We included two sources of carrier heating: free-carrier absorption of the coherent radiation in the cavity, and the power flux into the active layer, associated with the input current. Resulting from the very existence of modulated optical and electrical signals, these effects cannot be avoided in any laser structure. Simple analytic expressions have been derived for the intermodulation distortion in multichannel single-mode lasers. For an 80-channel 60-540 MHz system with 3% optical modulation depth per channel, the composite second-order (CSO) distortion brought about by the hot-carrier effects is near the tolerance limit for CATV systems     

Versatile,High‐Power,Flexible, Stretchable Carbon Nanotube Sheet Heating Elements Tolerant to Mechanical Damage and Severe Deformation

A macroscopic carbon nanotube (CNT) sheet‐based heating element having flexible, stretchable, and damage‐tolerant features, and wide applicability in harsh environments, is introduced. Because of the intrinsic connection of extremely flexible CNT bundles throughout the sample by van der Waals interactions without use of a binder, the electrical resistance variation of the CNT sheet on elastomer heating element as a function of strain is completely suppressed to some extent, even when stretched under up to 400% strain, which guarantees electrical stability under severe mechanical deformation. In addition, the spatial uniformity of the heat generated from the microaligned CNT bundles reduces the temperature variation inside the sample, which also guarantees thermal stability and operation at a higher average temperature. Such exceptional performance is achieved by the passivation of the elastomer layer on the CNT sheets. Furthermore, the mechanical robustness of this flexible, stretchable heating element is demonstrated by stable heater operation, even when the heating element is damaged. In addition, this design concept of CNT sheet on elastomer is extended to transparent flexible heaters and electric‐thermochromic windows.