宽光谱AOTF匹配网络对光谱衍射效率影响的研究

基于声光可调滤波器(acousto-optic tunable filter，AOTF)光谱成像分析仪在可见至红外光谱的多个谱区内广泛应用，对AOTF的光谱带宽及衍射效率提出了更高的要求。超声换能器作为AOTF的核心部件，其3 dB工作带宽决定AOTF的光谱衍射范围，故在同一声光介质上制作两片厚度不同的换能器来提高AOTF光谱带宽。由于超声换能器在不同频率下具有不同的输入阻抗，当驱动信号源输出阻抗与超声换能器输入阻抗失配时会产生能量损耗，导致无法把功率最大限度的传递给超声换能器，从而使AOTF光谱衍射效率降低，影响光谱成像清晰度。通过射频电路先进设计系统(ADS)仿真及实验测试，设计了一种新型宽带阻抗匹配网络，在60～200 MHz带宽范围内，阻抗匹配网络功率效率达到90％以上，光谱衍射效率最高达90％，提高了在420～1 150 nm波段内的光谱灵敏度。

The Study on the Influence of Spectral Diffraction Efficiency Based on the Matching Network of Wide Spectrum AOTF

Given that AOTF (Acousto‐Optic Tunable Filter ,AOTF) spectral imaging analyzer is widely used in a wide spectral region of the visible and infrared spectrum ,the spectral bandwidth ,diffraction efficiency and power efficiency of the AOTF need to be improved to meet higher standards .Ultrasonic transducer is the core component of AOTF .Its 3 dB working bandwidth de‐termines the spectral diffraction range of AOTF ,so it is making two different thicknesses high‐low frequency ultrasonic trans‐ducer to improve AOTF spectral bandwidth on the same of the acousto‐optic medium .Because between the operating frequency of ultrasonic transducer and input impedance there exists non‐linear relationship ,they have different input impedances at differ‐ent frequencies .When the between driving signal source’s output impedance and ultrasound transducer have mismatched ,It would produce energy consumption and lead to cannot bring the maximum power transfer to the ultrasonic transducer ,so that the spectral diffraction efficiency of AOTF is reduced ,and it affected spectral imaging quality .So going through to study theo‐retical ultrasonic transducer impedance frequency characteristics deeply in this paper designed a new broadband impedance matc‐hing network ,which has important application reference value of the spectral diffraction efficiency improving .By ADS simula‐tion and actual matching circuit experimental test ,experimental results show that impedance matching network’ power efficiency reach to more than 90% ,spectral diffraction efficiency get up to 90% in the 60~200 M Hz bandwidth ,and improve to spectral imaging quality within 420~1 150 nm waveband .The higher diffraction efficiency of the matching network has important impli‐cations for the current application AOTF based on spectral imaging technology .