Chirped-Pulse Interferometry - Enhanced Optical Imaging using Chirped Laser Pulses

生物医学成像需要高分辨率才能看到样本的精细特征，并且需要快速的采集速度，因为生命系统往往会四处移动。同时，它必须使用低功率，以避免对标本的伤害。光学相干层析成像(OCT)是一种利用光学干涉对生物样品进行非侵入性高分辨率三维成像的强大技术。干涉是两束光叠加时产生的亮和暗区域的图案。 OCT的分辨率由所使用的光干涉的长度决定。不幸的是，色散，即光的频率相关速度，通过加宽干涉特征和降低干涉对比度而损害成像分辨率。一种名为量子OCT(QOCT)的技术不受色散的影响，但需要量子力学纠缠的光子对。纠缠是涉及两个或更多粒子的量子力学系统的一种属性，不能单独描述。纠缠的需要极大地减少了可用于成像的光子数量，使得QOCT变得太慢而不实用。 啁啾脉冲干涉术(CPI)也不受色散的影响。脉冲是激光的短脉冲，持续时间只有十亿分之一秒的百万分之几。啁啾脉冲是指光的频率或颜色从脉冲的一端到另一端从红色变为蓝色。CPI具有比OCT更好的分辨率，自动色散消除，信号强度是QOCT的1000万倍。 CPI已经在实验室中进行了演示，但分辨率不够高，功率水平太高，无法与活样本一起使用。在拟议的项目中，我们将使用CPI建立一个原型装置，用于对生物样本进行色散抵消3D成像，其分辨率可与传统的OCT系统相媲美。这将是生物医学成像领域的一大进步。

Biomedical imaging requires high resolution to see the fine features of a sample and fast acquisition speed because living systems tend to move around. At the same time it must use low power to avoid harming the specimen. Optical coherence tomography (OCT) is a powerful technique which uses optical interference for non-invasive high resolution 3D imaging in biological samples. Interference is the pattern of light and dark regions created when two beams of light are superposed. The resolution of OCT is determined by the length over which the light used will interfere. Unfortunately, dispersion, the frequency dependent velocity of light, hurts the imaging resolution by broadening interference features and lowering interference contrast. A technique called quantum-OCT (QOCT) is immune to dispersion but requires quantum mechanically entangled photon pairs. Entanglement is a property of quantum mechanical systems involving two or more particles that cannot be described separately. The need for entanglement drastically reduces the number of photons available for imaging, making QOCT too slow to be practical. Chirped-pulse interferometry (CPI) is also immune to dispersion. A pulse is a short burst of laser light, lasting as little as a few millionths of a billionth of a second. A chirped pulse is one where the frequency, or colour, of the light changes from red to blue from one end of the pulse to the other. CPI has better resolution than OCT, automatic dispersion cancellation, and 10,000,000 times the signal strength of QOCT. CPI has been demonstrated in the lab, but with insufficient resolution and power levels too high to use with living samples. In the proposed project we will build a prototype setup using CPI for dispersion-cancelled 3D imaging of a biological sample, with a resolution comparable to conventional OCT systems. This will be a major advance in biomedical imaging.