【作者】 刘欣；

【导师】 娄存广； 邓朝；

【作者基本信息】 河北大学 ， 电子信息硕士（专业学位）， 2023， 硕士

【摘要】 随着光电探测应用场景的逐渐复杂化,工作在不同波段的光电探测器逐渐被集成用于目标物的宽光谱探测。受限于集成系统的体积大、任务模块多,常规的宽谱探测往往需要多个不同波段的探测器协同工作,这极大地增加了系统复杂度。因此,具有超宽带探测能力的低噪声光电探测器逐渐成为国际研究的前沿热点。基于热效应的探测器能够实现宽带光探测,但是对热噪声的抑制一直是一个技术瓶颈。光声效应也利用了光热吸收转换,具有探测宽带光的可能,基于高品质因数（Quality Factor,Q）石英音叉（Quartz Tuning Fork,QTF）光声效应（光致热弹效应）的光热探测器已被证明是实现弱光高灵敏探测的一种有效手段。QTF的光声信号幅值与石英音叉振臂的劲度系数直接相关,本文选用低劲度系数的微型石英音叉（miniature Quartz Tuning Fork,mQTF）探测器,研究利用其光声效应实现从可见光至太赫兹波段的高灵敏度光探测。mQTF的振臂为具有压电效应和逆压电效应的石英晶体,通过压电效应可将mQTF产生的光致热形变转化为电信号,最后经过锁相放大器进行信号解调,实现高灵敏度、低噪声的光声探测系统。基于mQTF的谐振探测可以有效抑制噪声,为开发低成本和高检测灵敏度的光电探测器提供了一种有前景的技术策略。首先,介绍了光声效应的产生及发展历程、mQTF光声效应的产生机理与光声效应理论知识等,为后续研究打下理论基础。使用仿真软件对mQTF的实际振动模态进行仿真,确定所选mQTF在特定频率下的振动模式,并探究mQTF振臂劲度系数与振动幅度的关系,确保整体研究方案的可行性,对衡量探测器性能的关键参数进行介绍。随后,设计了三套基于mQTF探测器的不同工作波长的光探测系统,研究了mQTF探测器在可见光、红外、太赫兹波段的响应灵敏度。在可见光波段,利用可见光光束功率强、辐照光斑小的优势,确定了mQTF探测器检测灵敏度最强的位置。在相同探测条件下,与普通QTF探测器进行对比,结果表明,mQTF探测器的信噪比是普通QTF的58.6倍。在1.32 m W的光辐照功率下,mQTF探测器的响应度为4.16×10³ V/W,噪声等效功率（Noise Equivalent Power,NEP）为4.2×10^-8 W·Hz^-1/2,响应时间为17 ms。为了更精确地探究探测器的宽谱响应特性,进行了聚苯乙烯的红外吸收光谱探测,并与商用热释电探测器扫描得到的光谱图进行对比,研究分析mQTF探测器的检测灵敏度和响应带宽。研究结果表明,mQTF探测器在3000 cm^-1（3.33μm）的响应度为509.4V/W,NEP为2.25×10^-7 W·Hz^-1/2,响应时间为20.8 ms。通过测量喇叭天线的空间电场分布研究了mQTF探测器在太赫兹波段的检测灵敏度与响应特性,获得了11.7 ms的响应时间,0.6μW的最小可探测功率,NEP为5.93×10^-7 W·Hz^-1/2。最后,为了进一步提升mQTF探测器的检测灵敏度,将mQTF探测器封装于屏蔽盒中。在4000 cm^-1～700 cm^-1波数范围内扫描了红外分光光度计灯丝的发射光谱,分析了mQTF探测器对整个红外波段光辐射的响应能力。通过扫描聚苯乙烯的红外吸收光谱并与分光光度计的光谱进行对比分析,研究了mQTF探测器在每一波数处的检测灵敏度提升。将mQTF探测器用于丙酮气体的红外吸收光谱探测,研究了其用于气体光谱表征的可行性。综上所述,本文提出的基于光声效应以及mQTF探测器的光探测技术将为宽带光谱探测,特别是对中红外和长波红外的探测提供了新的思路。更多还原

【Abstract】 With the increasing complexity of photoelectric detection application scenarios,photoelectric detectors working in different bands are gradually integrated for wide spectrum detection of targets.The integrated system is generally composed of many task modules,and the conventional wide spectrum detection often requires multiple detectors with different working bands,which greatly increases the system’s complexity.Therefore,low noise photodetector with ultra-wideband detection capability has gradually become the forefront of international research.The thermoelectric detector can realize wideband optical detection,but the suppression of thermal noise is always a technical bottleneck.The photoacoustic effect utilizes the optical absorption and thermoelastic conversion,it has broadband photodetection ability.The high-quality factor（Q）quartz tuning fork（QTF）based on photoacoustic effect（thermoelastic effect）has been proved to be an effective method to realize high sensitive wideband detection.The amplitude of the photoacoustic signal is directly related to the stiffness coefficient of the QTF’s prong.In this paper,a miniature quartz tuning fork（mQTF）with lower stiffness coefficient is selected for high sensitivity detection from visible light to terahertz band.The vibrating prong of mQTF is quartz crystal with piezoelectric effect and inverse piezoelectric effect,the photothermal deformation generated by mQTF can be converted into electrical signal through piezoelectric effect.Finally,the signal is demodulated by lock-in amplifier,realizing high sensitivity and low noise photoacoustic detection system.The mQTF-based photoacoustic resonant detection can effectively suppress noise and provide a promising strategy for the development of low cost,high sensitivity optical detection.Firstly,the generation and development of photoacoustic effect,the mechanism and the theoretical knowledge of mQTF’s photoacoustic effect were introduced,which laid a theoretical foundation for the subsequent research.The actual vibration mode of mQTF was simulated,and the relationship between mQTF’s vibrational stiffness coefficient and vibration amplitude was explored to ensure the feasibility of the research.Finally,the key parameters for evaluating performance of the detector were introduced.Subsequently,three sets of broadband light detection systems based on mQTF detectors were designed,and its response bandwidth and detection sensitivity in visible,infrared and terahertz bands was studied.In the visible band,the position with the strongest detection sensitivity of mQTF detector was determined by using the visible light beam with small irradiation spot and strong power.In the same detection scene,the comparison result show that the signal to noise ratio（SNR）of mQTF detector was 58.6 times higher than that of the ordinary QTF.Under the irradiation power of 1.32 m W,the measured responsivity of mQTF detector was 4.16×10³ V/W,the noise equivalent power（NEP）was 4.2×10^-8 W·Hz^-1/2,and the response time was 17 ms.In order to explore the broadband spectral response characteristics of the mQTF detector more accurately,the infrared absorption spectrum of polystyrene was measured,and it was compared with the result that obtained by the commercial pyroelectric detector.The response of mQTF detector at 3000 cm^-1（3.33μm）was measured to be 509.4 V/W,the NEP was 2.25×10^-7 W·Hz^-1/2,and the response time was 20.8 ms.The performance of the mQTF detector were then studied by measuring the spatial electric field distribution of the terahertz horn antenna.The results show that the response time of the mQTF detector was 11.7 ms,the minimum detectable power was 0.6μW,and the NEP was 5.93×10^-7 W·Hz^-1/2.Finally,in order to further improve the detection sensitivity,the mQTF detector was encapsulated in a shield box.The emission spectrum of the filament of infrared spectrophotometer was scanned in the wavenumber region 4000 cm^-1 to 700 cm^-1,and the response ability of mQTF detector to the whole infrared band light radiation was analyzed.The infrared absorption spectrum was obtained by scanning the polystyrene,and the improvement of detection sensitivity of mQTF detector at each wave number was intuitively demonstrated by spectral contrast analysis.Finally,the mQTF detector was used for infrared absorption spectrum detection of acetone gas,and the feasibility of spectral system based on mQTF detector for gas characterization was studied.In summary,the optical detection technology based on photoacoustic effect of mQTF detector will provide a new idea for bandwidth-free spectral detection,especially for mid-infrared and long-wave infrared detection.更多还原