Terahertz biophotonics by use of ultrafast telecommunication devices

本研究的目的是利用超快光子器件实现一种新型、紧凑、高精度的相干拉曼光谱仪，用于生物组织中太赫兹（THz）分子振动的体内检测，并展示其在生物光子学应用中的优势。首先，在传统纳秒脉冲CARS系统的基础上，研制了一种共焦太赫兹频率CARS光谱仪，对有机分子和生物分子在1.5 ~ 54太赫兹宽频率范围内的CARS光谱进行了测量和极化分析，建立了太赫兹生物光子学数据库。然后，我们开发了太赫兹- cars显微镜，并对癌症组织进行了近红外成像，以研究传统太赫兹成像获得的生物信息。从清晰、高分辨率的图像中，我们发现近红外成像不仅对癌症部分有效，而且对被癌细胞包围的坏死部分也有效。利用固体样品中的太赫兹声子共振，也首次证明了太赫兹cars成像。此外，我们已经开发了一个峰值功率，可调谐的近红外源使用皮秒脉冲激光二极管，光纤放大器，非线性频率转换使用光子晶体光纤和周期性极化铌酸锂。该紧凑、灵活的光源成功地应用于小鼠神经元细胞的非线性光学（双光子荧光）生物成像。通过这些卓有成效的成果，我们为太赫兹生物光子学奠定了新的基础，为太赫兹科学技术的发展做出了贡献。

The objectives of this research are to realize a novel, compact, high-accuracy coherent Raman spectrometer using ultrafast photonics devices for the in vivo detection of terahertz (THz) molecular vibrations in biological tissues, and demonstrate the advantages in biophotonics applications. Firstly, we developed a confocal THz-frequency CARS spectrometer based on the conventional nanosecond-pulsed CARS system, and then measured and performed polarization analysis of CARS spectra of organic and biomolecules in the wide frequency range of 1.5-54 THz, to obtain a database for THz biophotonics. We then have developed a THz-CARS microscope, and performed near-infrared imaging of a cancer tissue, to study the biological information obtained by conventional THz imaging. From the clear, high-resolution images, the near-infrared imaging was found to be effective for the detection of not only the cancer portions, but also the necrotic portions surrounded by cancer cells. Using THz-phonon resonances in solid samples, THz-CARS imaging was also demonstrated for the first time. Furthermore, we have developed a high-peak power, tunable near-infrared source using picosecond pulsed laser diode, fiber amplifiers, and nonlinear frequency conversions using a photonic crystal fiber and periodically poled lithium niobate. The compact, flexible light source was successfully applied to nonlinear optical (two-photon-fluorescence) bioimaging of mouse neuron cells. Through the above fruitful results, we have contributed to the new basis for THz biophotonics and the advance of THz science and technology.