Imaging by terahertz photon counting
Imaging by terahertz photon counting
复制标题
太赫兹光子计数成像
DOI：
10.1016/j.crhy.2010.06.009
复制
发表时间：
2010
影响因子：
1.4
通讯作者：
S. Komiyama
中科院分区：
文献类型：
--
作者：
K. Ikushima;K. Ikushima;S. Komiyama
对于光谱学研究，太赫兹区域（1 THz <$33 cm− 1或4 meV）因其所包含物质光谱的丰富性而与众不同。近年来，用于产生和控制THz波的技术已经被更新，例如几个新的发展，包括利用超短可见光激光脉冲产生THz波[1]，时域光谱[2]和半导体量子级联激光器[3]。这次翻新激发了关于太赫兹波在临床，安全和环境等不同领域的传感，成像和光谱学的可能应用的讨论[2，4-6]。由于室温操作是隐含在这些应用中，辐射处理是相对强烈的，远远超过黑体辐射在300 K（在10%的相对带宽中，大约10 - 7瓦或每平方厘米1014光子/秒）。除了日常生活水平上的这种应用之外，还可以有另一种重要的方法;也就是说，探测和研究最终微弱的太赫兹辐射。虽然天文学家长期以来一直采用这种方法，但基础研究领域的研究人员也可能受益匪浅。太赫兹辐射的光子能量小于室温下的热能（300 K时为25 meV）。因此，大多数物质在没有特别安排的条件下容易发射太赫兹辐射。如果物体处于热平衡，辐射光谱将类似于黑体辐射，因此，不感兴趣。然而，感兴趣的对象很少处于热平衡状态：大多数重要的效应，无论是物理，化学还是生物现象，都是非平衡状态的表现。在许多情况下，任何微观物体都可以从其环境中获取可用的能量，将能量转换为其固有的激发模式，产生太赫兹光子，其中信息被印记，并发射它们。通过灵敏的显微镜捕捉这些光子可能会大大有助于研究物体内部发生的局部现象。然而，在传统的显微镜方案中，物体受到外部源的照射：外部辐射强制物体的激发，阻碍物体的这种“本征”发射。因此，对于物质的内在动力学的研究，被动显微镜，其中没有外部照射的对象发出的辐射进行研究，是非常可取的。热成像法是被动方法的一个例子，但由于光谱和空间分辨率的限制，其应用受到限制。一般来说，被动显微镜迄今为止相对未开发，尽管其潜在的重要性。这是因为要检测的辐射可能非常微弱，并且没有足够灵敏的显微镜。但最近，情况开始发生变化。虽然超导传感器的发展正在将光子计数的光谱范围扩展到红外区域[7，8]，但光子计数已经在THz/GHz区域中用半导体量子点（QD）探测器实现[9，10]。因此，如果成功地将这些QD探测器与适当设计的显微镜相结合，那么在THz区域中的高灵敏度显微镜是可能的。光谱分辨率λ/λ< 0。05，最大灵敏度波长在λ= 120-170 μm范围内可磁调谐。实际测量中获得的最高灵敏度在λ = 130 μm处约为0.1计数/秒。这相当于每秒约有一个光子（或10− 21瓦特）入射到探测器上，其灵敏度大约是普通探测器的1000倍。
For spectroscopic studies, the terahertz region (1 THz∼ 33 cm− 1 or 4 meV) distinguishes itself by the richness of contained spectra of matter. Techniques for generating and controlling THz waves have been renovated in recent years, being exemplified by several new developments including the generation of THz waves exploiting ultra-short visible laser pulses [1], time-domain spectroscopy [2], and semiconductor quantum cascade lasers [3]. The renovation has stimulated discussion about possible applications of THz waves to sensing, imaging and spectroscopy in diverse areas like clinics, security, and environment [2, 4–6]. Since room-temperature operation is implicit in these applications, the radiation treated is relatively intense, being well beyond black-body radiation at 300 K (roughly 10− 7 watts or 1014 photons/s per square centimeter in a 10% relative band width).Aside from such applications on the everyday-life level, there can be another important approach; that is, to detect and to study ultimately weak THz radiation. While astronomers have long pursued this approach, researchers in basic research area of matters may benefit greatly as well. Photon energies of THz radiation are smaller than the thermal energy at room temperature (25 meV at 300 K). It follows that most matter readily emits THz radiation in not specifically arranged conditions. If the object is in thermal equilibrium, the radiation spectrum would be similar to that of black-body radiation, hence, uninteresting. However, objects of interest are rarely in a thermal equilibrium state: Most important effects, whether physical, chemical or biological phenomena, are manifestations of nonequilibrium states. In many conditions, any microscopic object may pick available energy from its environment, transform the energy into its intrinsic mode of excitation, create THz photons in which the information is imprinted, and emit them. Catching those photons via a sensitive microscope may contribute greatly to the study of local phenomena occurring within the objects. In conventional scheme of microscopy, however, an object is irradiated by an external source: the external radiation enforces excitation of the object, hindering such “intrinsic” emission by the objects. For the study of intrinsic dynamics of matters, therefore, passive microscopy, in which radiation emitted by the object without external irradiation is studied, is highly desirable. Thermography is one example of a passive method, but its application has been limited because of restricted spectral and spatial resolutions. In general, passive microscopy has so far been relatively unexplored despite its potential importance. This is because the radiation to be detected can be extremely weak and sufficiently sensitive microscopes were not readily available. Recently, however, the situation is beginning to change. While the development of superconducting sensors is expanding the spectral range of photon counting towards the infrared region [7, 8], photon counting has been realized in the THz/GHz region with semiconductor quantum-dot (QD) detectors [9, 10]. Highly sensitive microscopy in the THz region is hence possible if one successfully combines those QD detectors with appropriately designed microscopes. A spectral resolution of λ/λ< 0. 05 is obtained by a narrow bandwidth of the detectors, where the wavelength of the maximum sensitivity is magnetically tunable over λ= 120–170 μm. The highest sensitivity achieved in this actual measurement is about 0.1 count per second at λ∼ 130 μm. This corresponds to the incidence of about one photon per second, or 10− 21 watt, on the detector, and is roughly about 1000 times more sensitive than the …
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影响因子：
64.8
作者：
De Wilde, Yannick;Formanek, Florian;Greffet, Jean-Jacques
通讯作者：
Greffet, Jean-Jacques
影响因子：
4
作者：
Astafiev, O;Komiyama, S;Hirakawa, K
通讯作者：
Hirakawa, K
带有量子霍尔探测器的高灵敏度扫描远红外显微镜
DOI：
--
发表时间：
2003
期刊：
Rev. Sci. Instrum. 74
影响因子：
--
作者：
T.Machida;T.Yamazaki;K.Ikushima;S.Komiyama;小宮山 進;T.Machida;T.Machida;T.Machida;T.Machida;T.Machida;T.Machida;町田友樹;K.Ikushima;O.Astafiev;Y.Kawaguchi;T.Machida;K.Ikushima
通讯作者：
K.Ikushima
远红外/亚毫米波范围内量子点的单光子探测，“量子点中的电子传输”（§9）
DOI：
--
发表时间：
2003
期刊：
影响因子：
--
作者：
Astafiev;S. Komiyama
通讯作者：
S. Komiyama