Frequency-Tunable Terahertz-Wave Generation from GaP Using Cr:Forsterite Lasers

We have constructed THz spectrometers using the widely frequency-tunable THz-wave generated from GaP crystal pumped at 1.2 μm region using two Cr:forsterite lasers and compared with that pumped at 1 μm region using a YAG laser and an optical parametric oscillator (OPO). The systems have sufficient resolution for observation of solids and liquids at room temperature. We have measured Terahertz absorption spectra of all 20 kinds of amino acids which form proteins.     

FREQUENCY-TUNABLE TERAHERTZ-WAVE GENERATION FROM GaP USING Cr:FORSTERITE LASERS

We have constructed THz spectrometers using the widely frequency-tunable THz-wave generated from GaP crystal pumped at 1.2 μm region using two Cr:forsterite lasers and compared with that pumped at 1 μm region using a YAG laser and an optical parametric oscillator (OPO). The systems have sufficient resolution for observation of solids and liquids at room temperature. We have measured terahertz absorption spectra of all twenty kinds of amino acids which form proteins.     

GaP Raman Terahertz high accuracy spectrometer and its application to detect organic and inorganic crystalline defects

One of the most important uses of THz spectrometry is to detect defects in molecular structure or in crystals efficiently. We applied GaP Raman THz (GRT) spectrometer to detect and evaluate defects in inorganic and organic materials. High THz-wave absorption due to high defect density of GaSe crystal lowered the efficiency of THz wave generation, when the crystal is used as nonlinear material for DFG (Difference Frequency Generation). Defects in organic molecules could be observed as changes in frequency, intensities of the absorption, and broadenings of the spectra.     

高分辨X射线晶体谱仪及其在激光等离子体中的应用

对椭圆型聚焦晶体谱仪配X射线CCD相机的X射线谱测量系统进行了优化设计.优化设计后的椭圆型聚焦晶体谱仪系统的工作距离981.56 mm和摄谱范围0.133～0.756nm,并具有很好的谱分辨本领(λ/Δλ≥1000)和信噪比.新设计的椭圆型聚焦晶体谱仪首次在"神光Ⅱ"X光激光靶室上成功地获得了激光等离子体谱线信息并辨认和归类了一些离子的谱线,同时还给出了实验测定的谱仪能量分辨率.其中一些离子谱线诸如类离子共振线、伴线、互组合线和Ly-α线谱可为下一步诊断激光等离子体的电子温度和离子密度的空间分布轮廓打下了坚实基础.     

Wavelength dependent damage in biological multi-photon confocal microscopy: A micro-spectroscopic comparison between femtosecond Ti:sapphire and Cr:forsterite laser sources

Molecular excitation by the simultaneous absorption of two photons provides intrinsic three-dimensional resolution in laser scanning fluorescence microscopy. Thus induced two-photon absorption and the accompanied multi-photon absorption/ionization not only cause photo-bleaching but also cell damage in the vicinity of the focal point. In this paper, we study the wavelength dependent cell damage induced by high intensity femtosecond near infrared lasers. The study was performed with a Ti:sapphire laser and a Cr:forsterite laser. With a longer output wavelength from a Cr:forsterite laser, multi-photon absorption and auto-fluorescence were found to be significantly suppressed and the destructive plasma formation was found to be greatly reduced. Sustained multi-photon spectra can be observed in most plant specimens with a tightly focused Cr:forsterite laser beam under long term irradiation with more than 100 mW laser average power. In contrast, multi-photon absorption induced destructive plasma formation were frequently observed with a tightly focused Ti:sapphire laser beam within seconds with more than 10 mW laser average power.     

SBN:Cr晶体中孤子诱导的实时平面光波导及其导光特性分析

通过数值模拟和实验对SBN:Cr晶体中的（1+1）维亮屏蔽空间孤子及其诱导的实时平面光波导的导光特性进行了研究.采用分步束传播法和Petviashvili迭代法对（1+1）维亮屏蔽空间孤子的特性进行了模拟.通过求解本征方程,对孤子诱导平面波导中存在的导波模式进行了数值求解.采用633 nm的He-Ne激光作为孤子诱导光束,532 nm的半导体泵浦的固体激光作为探测光,在固液同成分的SBN:Cr晶体中进行了实验研究.实验结果和数值模拟的结果符合的很好.而且结果表明SBN:Cr晶体中红光诱导的波导可以作为实时光波导.     

Development of THz wave oscillation and its application to molecular sciences

In 1967, a THz wave was generated for the first time using a free electron laser; however, the device was too expensive to be used widely. The author published the idea of THz wave generation by use of resonating vibration between paired atoms in polymer or crystal in 1965, and succeeded with K. Suto to generate a 12 THz wave in 1983. In 1999, the author invited K. Kawase and H. Ito to Sendai RIKEN to realize the concept by use of dielectrics; in 2000, they succeeded in realizing a sweep generator. In the same year, the author suggested the idea of applying the THz wave to cancer diagnosis and treatment, particularly by improving heating selectivity: This enhances the effect of medications by raising only the temperature of the cancer itself, not of the surrounding atomic pairs in the neighborhood. These applications are expected to spread quickly as powerful methodology based on molecular science. The reason for this is that the much improved waveform generated enables higher selectivity, allowing the detection of the existence of abnormal polymer near the paired atoms by measuring resonating frequency between paired atoms.     

光栅摄谱仪的改进及其在周期性极化的铌酸锂晶体倍频研究中的应用

由于电荷耦合器件(CCD)具有光谱响应范围宽、检出限低、动态范围宽、暗电流和读出噪声低以及具有积分信号、多道同时检测和实时检测等能力的优点,在光谱测量和光谱成象领域获得了广泛的应用。将传统的1m光栅摄谱仪和科学CCD相结合,使其具有实时快速测量激光光谱的能力。将其应用于宽带双包层光纤激光在周期性极化的LiNbO₃晶体(PPLN)中倍频特性的研究,观察到了倍频激光光谱随PPLN控制温度的动态变化过程,并对此进行了详细分析。