Stimulated Raman hyperspectral imaging based on spectral filtering of broadband fiber laser pulses

We demonstrate a technique of hyperspectral imaging in stimulated Raman scattering (SRS) microscopy using a tunable optical filter, whose transmission wavelength can be varied quickly by a galvanometer mirror. Experimentally, broadband Yb fiber laser pulses are synchronized with picosecond Ti:sapphire pulses, and then spectrally filtered out by the filter. After amplification by fiber amplifiers, we obtain narrowband pulses with a spectral width of <3.3 cm(-1) and a wavelength tunability of >225 cm(-1). By using these pulses, we accomplish SRS imaging of polymer beads with spectral information.     

Optimization of a distributed feedback dye laser system to generate single tunable picosecond pulses from UV to IR

We report a new configuration of a picosecond distributed feedback dye laser system, which can be pumped by various wavelengths. The optical characteristics of the system are presented. By using a triangle mirror functioned beam splitter and a right-angle prism attached to the front face of the cell in the pumping geometry, continuously and widely tunable laser wavelengths have been obtained for a range of more than 100 nm. A quenching mirror adhered to a face on the side of the cell, functioning as a high-Q cavity shared common gain medium, has been employed to observe single short laser pulses with transform-limited bandwidth.     

High power tunable picosecond green laser pulse generation by frequency doubling of an Yb-doped fiber power amplifier seeded by a gain switch laser diode

A compact tunable high power picosecond green laser pulse source based on frequency doubling of an Yb-doped fiber amplifier seeded by a gain switch laser diode has been developed. The fiber amplifier generates the picosecond infrared pulses with average power of 10.3 W, repetition rate of 1 MHz, pulse duration of 150 ps, and tunable range of 20 nm around 1064 nm. For underwater use, the tunable output infrared pulses are frequency doubled into picosecond green laser pulses, which can be tuned from 527 to 537 nm with average power of more than 1.1 W, corresponding to an overall conversion efficiency of 10.7% by a BBO nonlinear crystal. This kind of laser source will have potential application for underwater optical communication.     

Direct Generation of Tunable UV Picosecond Laser Pulses Using Spectrotemporal Selection

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利用皮秒脉冲激光驱动瞬态X射线激光

报道了利用皮秒激光驱动产生瞬态类镍银X射线激光的实验结果.采用一路脉冲宽度为数百皮秒的激光作为预脉冲，配合另一路皮秒激光作为主脉冲联合驱动平面靶，获得了一定强度的类镍银X射线激光输出，输出能量约为5—10nJ. 关键词： 瞬态X射线激光 长短脉冲联合驱动 皮秒脉冲激光     

多色双光子激发荧光显微技术实验研究

双光子激发荧光(two-photon excited fluorescence, TPEF)显微是一种非线性光学显微技术, 具有高的时间分辨率和空间分辨率、高的信噪比和固有的三维层析分辨能力等优点. 传统的TPEF显微一般采用波长可调谐的超短脉冲激光器作为光源. 在实际应用中, 利用TPEF显微技术研究含有多种荧光团或未知成分的待测样品, 往往需要多次改变激发光的波长以获得对各种荧光团的最佳激发. 为了同时获取不同荧光团的荧光信号, 利用超连续谱激光光源实现了多色TPEF显微成像, 实验中无需调节波长, 能够同时获得具有两种不同发射波长的荧光标记的铃兰根茎切片样品的TPEF图像. 实验结果表明, 与传统的TPEF显微相比, 该方法能够同时获取含有多种荧光团的待测样品的高对比度TPEF图像, 具有系统结构简单、操作简便、信息量大等优点, 在生物医学和材料科学等领域具有广阔的应用前景.     

核黄素与NADH在紫光波段的激光诱导荧光光谱研究

基于细胞代谢荧光体的激光诱导荧光探测,在生物反应过程监测与生物活性物质探测中具有广泛的应用.本文利用波长可调谐激光光源,结合液体射流进样装置,研究了核黄素与NADH等生物荧光体在紫光波段(389 nm～404 nm)激发的荧光光谱,并考察了激光强度、样品浓度等参数对荧光光谱特性的影响.实验观察到核黄素的激发光谱在402.5 nm处出现"波谷",具有特征性,选择403.5 nm激光激发,核黄素的浓度灵敏度约为NADH的八百分之一.这些结果为发展生物荧光探测与识别技术提供了新的基础数据.     

核黄素与NADH在紫光波段的激光诱导荧光光谱研究

基于细胞代谢荧光体的激光诱导荧光探测,在生物反应过程监测与生物活性物质探测中具有广泛的应用.本文利用波长可调谐激光光源,结合液体射流进样装置,研究了核黄素与NADH等生物荧光体在紫光波段(389nm～404nm)激发的荧光光谱,并考察了激光强度、样品浓度等参数对荧光光谱特性的影响.实验观察到核黄素的激发光谱在402.5nm处出现“波谷”,具有特征性,选择403.5nm激光激发,核黄素的浓度灵敏度约为NADH的八百分之一.这些结果为发展生物荧光探测与识别技术提供了新的基础数据.     

腔内带圆形空心波导的可调谐窄带脉冲染料激光器

本文报道了一种腔内带圆形空心波导和掠入射光栅的可调谐窄带脉冲染料激光器;实验结果表明:该激光系统能获得基横模、窄频带和高效率的激光输出。文中对系统设计机理也进行了分析。     

Sub-38 nm resolution tabletop microscopy with 13 nm wavelength laser light

We have acquired images with a spatial resolution better than 38 nm by using a tabletop microscope that combines 13 nm wavelength light from a high-brightness tabletop laser and Fresnel zone plate optics. These results open a gateway to the development of compact and widely available extreme-ultraviolet imaging tools capable of inspecting samples in a variety of environments with a 15-20 nm spatial resolution and a picosecond time resolution.     

A tunable picosecond IR laser generating multi-megawatt pulses in the range 3–8 m

We describe a versatile infrared laser system capable of generating picosecond pulses continuously tunable over the wavelength range 3.3–8.4 μm, with peak powers of 1–20 MW. The IR pulse duration is ～1.3 ps with a time-bandwidth product of ～0.3. The system uses stimulated electronic Raman scattering (SERS) in caesium vapour to shift the frequency of a picosecond dye laser into the infrared. The quantum efficiency of the Raman conversion process exceeds 40% over almost the entire tuning range. This technique can be extended to other tuning ranges in the IR by using different atomic vapours and SERS transitions.     

新型双环腔结构可调谐全光波长转换器的实验研究

利用周期性畴反转铌酸锂光波导级联和频与差频的二阶非线性效应，提出并实验验证了一种新颖的基于无源光波导双环腔结构的可调谐全光波长转换方案，实现了皮秒脉冲从信号光波长到空闲光波长的转换.采取的脉冲信号光脉宽为1.57ps，重复频率为40GHz，抽运光和控制光由双环腔激光器提供，无需任何外界注入连续光. 关键词： 全光波长转换器 双环腔 周期性畴反转铌酸锂 级联和频与差频二阶非线性效应     

Fluorescence lifetime system for microscopy and multiwell plate imaging with a blue picosecond diode laser

We report a wide-field fluorescence lifetime imaging (FLIM) system that uses a blue picosecond pulsed diode laser as the excitation source. This represents a significant miniaturization and simplification compared with other time-domain FLIM instruments that should accelerate the development of clinical and real-world applications of FLIM. We have demonstrated this instrument in two configurations: a macroimaging setup applied to multiwell plate assays of chemically and biologically interesting fluorophores and a microscope system that has been applied to imaging of tissue sections. The importance of the adjustable repetition rate of this laser source is discussed with respect to noise reduction and precision in the lifetime determination, illustrating a further significant advantage over conventional mode-locked solid-state lasers.     

Confocal fluorescence lifetime imaging of free calcium in single cells

Ca²⁺ concentrations in biological cells are widely studied with fluorescent probes. The probes have a high selectivity for free calcium and exhibit marked changes in their photophysical properties upon binding. The differences in the fluorescent lifetime of the probes can now be used as a contrast mechanism for imaging purposes. This technique can be further exploited for the quantitative determination of ion concentrations within the cells. We describe the use of a fast fluorescence lifetime imaging method in combination with a standard confocal laser scanning microscope for the determination of Ca²⁺ concentrations in single rat cardiac myocytes using the intensity probe Calcium Green.     

Short-pulse laser interferometric measurement of absolute gas densities from a cooled gas jet

We report on the use of a novel technique to measure the gas density from a pulsed gas jet. Deuterium gas is fully ionized with an intense picosecond laser, and the resulting electron density is measured by interferometric probing with a second picosecond pulse. We have applied this technique to characterize a cryogenically cooled, high-density gas jet.     

单到单和单到双信道皮秒脉冲全光波长转换的实验研究

基于周期极化反转铌酸锂（PPLN）光波导级联倍频和差频（SHG+DFG）的二阶非线性效应,提出并实验研究了皮秒脉冲的可调谐波长转换以及单信道到双信道的波长转换.信号光采用重复频率为40 GHz,脉宽为1.57 ps的脉冲信号.连续抽运光由光纤环形腔激光器（FRL）提供.不同于传统的SHG+DFG型波长转换,信号光固定在PPLN光波导倍频过程的准相位匹配（QPM）波长处,通过调节抽运光的波长实现了转换空闲光的可调谐输出.当使用两个抽运光时实验观察到了单信道到双信道的波长转换.     

A picosecond dye laser tunable in the 1.1μ m region

We report in this letter the characteristic of a picosecond dye laser, tunable in the 1.08–1.12 μm range. The dye is pumped by the fundamental of a mode-locked Nd-YAG laser. The energy conversion efficiency is higher than 10% and the pulse duration is less than 10 ps.     

Generation of high-order rotational lines by four-wave Raman mixing using a high-power picosecond Ti:Sapphire laser

More than thirty rotational lines equally spaced by 587 cm^–1 are generated simultaneously in the vicinity of the fundamental line by four-wave Raman mixing using a high-power picosecond Ti:Sapphire laser as a pump source and hydrogen as a Raman medium. Since the wavelength of this multifrequency laser emission extends from the near-infrared to the near-ultraviolet, it can be utilized as a tunable light source for picosecond spectroscopy. Because of the wide spectral bandwidth available, this procedure has great potential for the generation of ultrashort laser pulses by mode-locking these emission lines.     

Two photon resonant third harmonic generation in calcium vapour

We have generated ultraviolet picosecond pulses by frequency tripling a mode locked dye laser in calcium vapour. Saturation of third harmonic generation is observed when the dye laser is turned to a two photon resonance. Peak powers of 100 kW, tunable around 200 nm are achieved at fundamental powers of 250 MW.     

Picosecond X-ray radiography of superdense high-temperature laser plasma

The layout of an X-ray source for diagnostics of the compressed state of laser plasma is proposed, and its optimal parameters are calculated under the conditions required for nuclear fusion. Such a source operating in a pulsed regime is intended to be used for determining the spatial distribution of laser-plasma density with high temporal resolution by means of multiframe (pulses follow with a specified time interval) backlight imaging of the main target by X-ray pulses obtained by irradiation of a secondary target by picosecond laser pulses.