紫外可见光谱法测量高反射材料的绝对反射率

电介质多层反射镜是由高折射率和低折射率材料的组合组成的层压光学器件。利用干涉效应，这种反射镜可以在特定波长范围内提供极高的反射率（接近100%）。由于这些反射镜广泛用于相机、望远镜和光学通信设备，以减少光强损失，因此以非常高的精度评估材料的反射率非常重要。Application Note Absolute Reflectance Measurement of aHighly Reflective Material2/3Application Note UV-O043 Absolute Reflectance Measurement of a Highly Reflective Materia l Intro d uc t ion Dielect r ic mult i layer mirrors are laminated o p tics com p rising o f a combin a t i on of h ig h r e fract i ve index and l ow r e fra cti ve i ndex m ate r ia l s. Usi n g the i n t erf e rence ef f e c t， this m irror can provide e xt r eme l y hi g h r eflectance (n ear 100%) in a specif i c wavel e ngth range (F i gur e 1). Since t h ese mirrors are wid e ly used in cameras， telescopes， and optica l commu n ications devices to r educe the loss in lig h t i n t ensity， it is i mportant to evaluate the material 's reflectance with very h i gh accuracy. UV-Vis i b l e Spec t rophotometer nj ： h igh refractive i ndex nz ： low refractive index Figure 1. Sc h emat ic of t h e d i electr i c mul ti la yer mir r o r. The absolu t e r ef l ectance measureme n t system a nd the V-700 Series UV-Visible spectrophotometer provide high photomet r ic sta b i l ity f or acc u rate measureme n ts . T h e absolu t e ref l ectance system c a n perform measurements at arbitrary and use r -selected inc i dent angles， allowing th e measurement of die l ect r ic multilayer mi r rors at specific inc i dent angles. This application note demonstrates the use absolute reflectance measurement system for obtaining highly reflective measurements for a dielectr i c m u ltilayer m irr or. Keyword s V-750，U V -V i s ibl e /NIR，Abso l u te r eflectance， Mater i a l s Exp e rimental A dar k measurement was performed with a light -s h ielding p late， the base l in e measuremen t was per f ormed against air，and then the sample measurement obtained. This procedure wa s r epeated t h ree times a t the conditions listed below. Bandwidth 5nm Response Time 3.84 seconds Data Interval 1nm Scan Speed 20 nm/min Incident Angle 10° Polarization p-polarized light Results F i gure 2 sho w s a n ove r lay of th e absolu t e r ef l ectance o f th e d i elect r ic multilaye r mi r ror and Fi g u re 3 is a zoomed in v i ew of t h e sa me sp ectr a . T h e me as u r e m e n t r e p e a t a bil it y o f t h e s y s t e m i s ve r y hi g h an d T ab le 1 co mp a res th e th e o r e t i ca l a nd me a s ur ed r eflect a nce v alu e s . Th e d i ffe r e n ce b e twee n t he m e a su r em e n t a ve r a g e r ef l ect a n c e v a lue a n d th e t he o re ti ca l va lu e is g r eater th an 0.15%， in dicating tha t the absolute r eflectance s y s t em has h igh acc u racy and g oo d cor r e l a ti o n fo r re flectan c e m e a s u r e m ent s c l o s e t o 100%R . Figure 2. A b s olu te re fl ec t an c e s p e c t r a o f t he di e l e c tric mul t i l ay er mi r ror. JASCO INC. 28600 Mary's Cour t ， E a s to n ， M D 21601US A UASGO Figure 3. Ab s ol ute r eflec tan c e spectr a of t he d ie l ect r ic mult i la yer mi r r or ~100%R . Table 1. C ompa r iso n of t h e o ret ica l a n d me as ure d ref l e c t anc e v al u e s. Wavelength ExpectedValue %R Measurement Value %R Average%R StandardVariation VariationCoeffecient% DifferenceBetween Expected andAverage 1 2 3 680 99.9914 99.8663 99.8537 99.8407 99.8536 0.013 0.013 -0.1378 700 99.9918 99.8892 99.8943 99.8578 99.8804 0.020 0.020 -0.1114 720 99.9839 99.9094 99.9316 99.8889 99.9100 0.021 0.021 -0.0739 JASCO INC. 28600 Mary's Cour t ， E a s to n ， M D 21601US A UASGO