Amplification of Picosecond Pulses in Neodymium-doped Single-mode Optical Fibres

Abstract

The picosecond pulses from the output of a fibre-grating pair compressed mode-locked c.w. pumped Nd : YAG laser have been amplified in a neodymium-doped single mode optical fibre using a counter propagating c.w. pump geometry. Gains of up to times ten were measured in a 2·5 m fibre length for input signal energies of up to 0·2 pJ per pulse.     

色散渐减光纤压缩光脉冲

利用色散补偿光纤（ＤＣＦ）及色散位移光纤（ＣＳＦ）压缩重复频率为２．５ＧＨｚ的增益开关量子阱ＤＦＢ半导体激光器出射的光脉冲，将光脉冲由５３．８ｐｓ压缩至２．５ｐｓ，而后利用色散渐减光纤将２．５ｐｓ的光脉冲进一步压缩至０．８３ｐｓ。     

Optical Double-resonance Spectra with Time-dependent Pulses

Abstract

The optical double-resonance spectrum for a three-level atom interacting with two monochromatic laser pulses with arbitrary temporal profiles is calculated by use of Light's perturbation theory. Unlike some earlier work, the theory is not restricted to exact resonance of the pump laser, or to pulse areas which are exact multiples of 2π. A variety of pulse profiles are investigated, and the spectra are found to depend strongly on the detuning of the pump laser.     

Generation of Optical Harmonics by Intense Pulses of Laser Radiation

Abstract

We discuss effects of optical depth, beam focusing and non-perturbative atomic response on the spectrum of optical harmonics generated by an intense beam of laser radiation (up to 10¹⁴W cm^?2) in a small volume of atomic vapour. We find remarkable enhancement of high harmonics at intensities beyond the perturbative limit.     

可调蓝光皮秒脉冲

利用３５１ｎｍ紫外光泵浦非临界相位匹配ＬｉＢ３Ｏ５光参量振荡器（ＬＢＯ－ＯＰＯ）,直接获得了在４７２￣４５３ｎｍ范围内波长连续可调的蓝图光皮秒脉冲序列。ＯＰＯ所用ＬＢＯ晶体的两端面切割成Ｂｒｅｗｓｔｅｒ角,避开了晶体表面增透膜的稳定性问题,保证了ＬＢＯ晶体端面低反射损耗和ＯＰＯ长期稳定工作。     

五氮齿金属配合物溶液对皮秒激光的光限幅

报导了五种五氮龄金属配合物对３５ｐｓ激光光限幅的实验结果,限幅机制属于激发态的反饱和吸收。在实验所用较高激光能量时,没有观察到样品被损坏的现象。配合物「（ＡＰＰＣ－ＣＯＯＨ）Ｃｄ」Ｃｌ（Ⅰ）和「ＡＰＰＣ－ＮＰ）Ｃｄ」Ｃｌ（Ⅱ）的光限幅阈值分别为４４．１ｍＪ／ｃｍ＾２和１４６ｍＪ／ｃｍ＾２,配合物Ⅰ最代非线性透过率达９％。吸电子基团能增强该类配合物对皮秒激光的限幅效果,而重原子效应则起相反的作用。     

Frequency Modulated Continuous Wave System for Optical Fiber Intensity Sensors With Optical Amplification

We report on the use of erbium doped fiber (EDF) amplification to enhance a frequency modulated continuous wave (FMCW) technique for referencing optical intensity sensors located between two Bragg grating structures. The experiment combines the concept of FMCW with the spectrally selective mirror properties of Bragg gratings to interrogate with referencing properties intensity based sensors. The interrogation system without amplification yields a sensor resolution of around 0.078 dB. When the EDF amplifier is introduced into the experimental set up, the sensor sensitivity does not change, but the signal-to-noise ratio is improved, resulting into an enhanced resolution of 0.025 dB. We also obtain a remote sensing operation at a location of 50 km, showing the feasibility of this configuration to be used as a remote sensing application.     

Features of the Time Shape of the Pressure Pulses of Optical Air Breakdown

The time shape and amplitude of pressure pulses initiated by surface laser air breakdown for different energies of laser pulses (1–180 mJ) has been compared to the results of numerical gasdynamic calculations of unsteady explosive motions with allowance for counterpressure at distances of 0.2 to 30 cm from the breakdown region. It has been established that the experimental pressure pulse has the character of slowly damped quasiperiodic vibrations, whereas the calculated pulse is a bipolar single pulse of a much shorter duration. Good agreement between the experimental and calculated amplitudes of a positive pressure phase has been found throughout the investigated range, whereas the agreement between the corresponding amplitudes and durations of a negative pressure phase is limited in character. The differences observed in the experimental and calculated data have been attributed to the transformation of the shockwave motion to acoustic radiation.     

Multipass Amplification Using Optical Phase Conjugation by Stimulated Brillouin Scattering

Abstract

We built up a multipass amplifier for multiplication of infrared nanosecond pulses based on stimulated Brillouin scattering in acetone. Starting with a Q-switched Nd-doped yttrium aluminium garnet oscillator emitting pulses with less than 5 ns duration, we were able to generate a train of up to five pulses with a pulse shortening. Because only phase-conjugating mirrors have been used, we expect the pulses to have a high transverse homogeneity.     

Stimulated Raman Scattering and Self-phase Modulation of Ultrashort Light Pulses in Optical Fibres

Stimulated Raman scattering of picosecond pulses in optical fibre is investigated, with account taken of pulse walk-off by group velocity dispersion, pump depletion and chirp production by the intensity-dependent refractive index. An analytical solution of the basic equation is given by which the characteristic parameters of the Stokes and pump pulses, such as pulse half-width, intensity, mid-frequency and chirp, are calculated. It is shown that the chirp of the Stokes pulse does increase faster than that of the pump pulse with increasing fibre length and may surpass it by nearly three times after the pulse walk-off.     

Optical Amplification and Spontaneous Emission in an Ar + Discharge

The relationship between optical amplification and spontaneous emission noise has been studied in an argon ion travelling wave amplifier by beat spectrum analysis. Different optical arrangements have been examined with both single and double pass amplification. The results establish that when coherent light travels through a gain tube, the amplified beam acquires intensity fluctuation noise which is greater than that of a Poissonian distribution (shot noise). The noise power is shown to be the same as that of an equivalent unamplified beam mixed with the amplified spontaneous emission from the gain tube. It is shown that such measurements provide a practical technique for the otherwise difficult determination of the degree of population inversion in the gain medium. They also give insight into the potential of optical amplifiers for enhancement of lidar and system performance.     

On the Use of Non-fourier Eigensignals for Measuring Short Optical Pulses by Photomultiplier Tubes

Abstract

In this paper we show that the envelopes of short optical pulses detected by conversion of photomultiplier tubes-secondary electrons into single-frequency decayed oscillations may be presented by a set of orthogonal non-Fourier eigensignals. The enhanced temporal resolution estimated is of the order of (10–1) ps. A calculation of an optical receiver based on the commercial multianode microchannel plate photomultiplier-photomultiplier tubes is given. The method may be successfully applied in such areas as picosecond lidars, fibre optics, time-resolved spectroscopy etc.     

纳米颗粒与铒共掺光放大用材料的研究进展

掺铒材料由于在光放大领域的重要应用引起人们极大的研究兴趣,在掺铒材料中再掺入纳米颗粒能有效增强Er3+的发光强度.综述了各种纳米颗粒对Er3+发光光谱的敏化作用,阐述了纳米颗粒与Er3+之间的能量传递机理,展望了光放大材料的最新发展趋势.     

Femtosecond Traveling-Wave Optical Parametric Amplification in MgO:LiNbO(3)

A mid-infrared femtosecond optical parametric amplifier tunable in the chemically important spectral region between 3.1 and 3.9 mum (at >10-muJ idler pulse energy) has been constructed on the basis of MgO:LiNbO(3) with 7% doping. With femtosecond pumping near 800 nm (Ti:sapphire regenerative amplifier) and narrow-band (long-pulse) seeding, this simple single-stage device provides maximum conversion efficiencies of 40% and exhibits extremely low seed threshold (<10-mW peak seed power for >1-muJ idler output). The generated idler pulses are almost transform limited with <200-fs pulse duration. The pulse-to-pulse fluctuations reproduce the stability of the pump source at 1-kHz repetition rate.