Tunable ultraviolet generation using a femtosecond 250 kHzTi:sapphire regenerative amplifier

A mode-locked Ti:sapphire regenerative amplifier system pumped with a single argon ion laser produces μJ energy femtosecond pulses of 800 nn wavelength at up to 300 kHz repetition rate. This output is used to generate tunable femtosecond pulses in the ultraviolet to as short as 240 mn by using a combination of harmonic generation, white-light continuum generation and parametric amplification. A variety of techniques to access different parts of the UV spectrum are presented     

Sub-100 fs Kerr lens modelocked Cr4+:YAG laser

Sub-100 fs pulse generation from a Kerr lens modelocked Cr⁴⁺ :YAG laser has been demonstrated for the first time, yielding femtosecond pulses tunable from 1.49 to 1.56 μm with pulses as short as 90 fs obtained at 1.53 μm     

Tunable infrared generation using a femtosecond 250 kHz Ti:sapphireregenerative amplifier

A mode-locked Ti:sapphire regenerative amplifier system pumped with a single argon ion laser produces μJ energy 100 femtosecond pulses of 800 nm wavelength at 250 kHz repetition rate. Pumping a Type II BaB₂O₄ (BBO) optical parametric amplifiers (OPA) with this output generates 500 nJ infrared pulses and continuous tuning from 1.1 μm to beyond 2.5 μm. Difference frequency generation of the signal idler output from this OPA source in AgGaS₂ produces 60 nJ mid infrared pulses and continuous tuning from 2.4 μm to beyond 12 μm     

Tunable dual-wavelength picosecond optical pulses generated from aself-injection seeded gain-switched laser diode

A novel scheme to generate dual-wavelength picosecond optical pulses has been demonstrated. The pulses are obtained by self-injection seeding of a gain-switched laser diode simultaneously at two different wavelengths. Optical feedback is provided by a partially reflecting fiber mirror. Single-mode pulses at alternate wavelengths around 1.3 μm have been generated. The pulse width varies from about 40 to 50 ps. The output wavelengths can be tuned by changing the electrical modulation frequency. Spacing between the wavelengths can also be controlled by adjusting the length of the dispersive fiber cavity. Our experimental data are in good agreement with the calculated results     

Low-noise amplification of high-power pulses in multimode fibers

Low-noise amplification of high-power pulses in multimode erbium/ytterbium-doped fibers is demonstrated. The use of multimode fiber amplifiers allows to overcome the peak power limitations of single-mode amplifiers. As a result femtosecond pulses can be efficiently amplified to peak powers >50 kW in a high-power chirped pulse amplification system using chirped PPLN for frequency-doubling. With an average power level of 1.2 W at the fundamental wavelength of 1.55-μm average powers up to 420 mW are generated at 775 mm     

Short-pulse, high-power Q-switched fiber laser

A high-power, laser-diode-pumped, Q-switched fiber laser operating at 1.053 μm which is suitable for use in time-multiplexed fiber sensor applications is described. The laser emits >1-kW pulses at 1.053 μm with 2-ns duration at up to 1-kHz repetition rates for an adsorbed pump power of only 22 mW at 810 nm. Tunable Q-switched operation over a 40-nm wavelength range has also been demonstrated     

Simultaneous generation of wavelength tunable two-coloredfemtosecond soliton pulses using optical fibers

Wavelength tunable two-colored femtosecond (fs) soliton pulse generation is proposed and demonstrated for the first time, using passively mode-locked fs fiber laser and polarization maintaining fibers. The wavelengths of the two soliton pulses can be changed arbitrarily by varying the power and polarization direction of the fiber-input pulse. Ideal two colored soliton pulses in which the pulsewidths are about 200 fs are generated in the wavelength region of 1.56-1.70 μm for 110-m fiber. The generated pulses are almost transform-limited ones     

1.3-μm Pr-doped In-Ga-based fluoride fiber amplifiers pumped bygrating-fiber-pigtailed 0.98-μm-band laser diodes with a detunedwavelength of 1 μm

At most efficient pump wavelength, a praseodymium-doped In-Ga-based fluoride fiber is directly pumped by four 0.98-μm-band laser diodes. These lasing wavelengths are detuned from 0.98 to 1 μm by external selective optical feedback from fiber grating reflectors. Maximum signal output power of +13.5 dBm is obtained at 1.296 μm. Four-wavelength multiplexed signals at 1.296-1.311 μm are amplified with a deviation of gain less than 1.9 dB. By using the amplifier as a power booster, data of 2.5 Gb/s is successfully transmitted more than 100 km     

High-power mid-infrared supercontinuum sources: Current status and future perspectives

Mid-infrared (mid-IR) supercontinuum (SC) sources have recently gained much interest, as a key technology for such applications as spectral molecular fingerprinting, laser surgery, and infrared counter measures. However, one of the challenges facing this technology is how to obtain high power and broadband light covering a spectral band of at least 2–5 µm, especially with a very efficient output power distribution towards the mid-IR region. This directly affects their usage in the practical applications mentioned above. Typically, an SC is generated by pumping a piece of nonlinear fibre with high-intensity femtosecond pulses provided by mode-locked lasers. Although this approach can lead to wide continuum generation, the output power is limited only to the milliWatt level. Therefore, to achieve high-power SC light, other laser systems need to be employed as pump sources.This paper briefly reviews SC sources, restricted to those with an average output power of over 0.4 W and simultaneously with a long-wavelength edge of the continuum spectrum of over 2.4 µm. Firstly, the concepts of SC generation, including the nonlinear phenomena governing this process and the most relevant mid-IR fibre materials, are presented. Following this study, a review of the main results on SC generation in silica and soft-glass fibres, also including my experimental results, is presented. Emphasis is given to high-power SC generation with the use of different pump schemes, providing an efficient power distribution towards longer wavelengths. Some discussion and prospective predictions are proposed at the end of the paper.     

Modulation instability and soliton-Raman generation inP2O5 doped silica fiber

Generation of high-repetition-rate modulation instability pulse trains and high- energy soliton-Raman pulses of ≃60 fs durations, in a single-mode P₂O₅-doped silica fiber, is reported. The 7 mol.% concentration P₂O₅ fiber was pumped in a single pass arrangement by a Q-switched and mode-locked Nd:YAG laser operated at 1.319 μm. Operating in the region of zero second-order dispersion, modulation instability Stokes sideband seeded resonantly cascade stimulated Raman scattering associated with Si-O-Si and P=0 vibration modes of the fiber. As a result, broad bandwidth and widely tunable 1.36-1.80 μm femtosecond pulses were obtained     

Optical gain in Er-Yb doped waveguides fabricated by femtosecondlaser pulses

Er-Yb doped waveguides at 1.5 μm fabricated by femtosecond laser pulses are reported. Demonstrated is a Gaussian mode-profile, low propagation loss and internal gain in a 25 mm-long waveguide used as the active element in a standard waveguide-amplifier setup     

Generation of ultrashort pulses from a neodymium glass laser system

A neodymium glass laser system capable of generating high-energy, ultrashort pulses at a convenient repetition rate is described. The effect of nonlinear frequency pulling on active mode locking is discussed. By minimizing the nonlinear frequency pulling, it is possible to routinely generate stable ~10-ps pulses at a 100-MHz repetition rate from the actively mode-locked oscillator. The regenerator amplifier increases the oscillator pulse energy to over 30 μJ at a 370-Hz repetition rate. Using intracavity self-phase modulation, the regenerative amplifier also broadens the pulse bandwidth to ~35 Å. By subsequent pulse compression while maintaining high energy, it is possible to produce 0.55-ps pulses with >10 μJ. An optical fiber pulse compressor further shortens the pulses to 30 fs (30 nJ), the shortest pulses ever generated at 1.054 μm from a neodymium laser system     

全固态近红外、蓝光飞秒激光系统的实验研究

利用棱镜对引进频谱空间啁啾来补偿飞秒激光二次谐波产生中的相位失配,提高了倍频效率.建立了一套全固态、多波长(1064 nm,532 nm,823 nm,402 nm)飞秒脉冲激光系统.NdYVO4激光器输出的1064 nm激光功率可达10 W;532 nm绿光激光最高功率可达5.6 W.当用2.5 W绿光激光泵浦时,从钛宝石激光器及经BBO倍频可分别输出中心波长为823.1 nm和402 nm、平均功率300mW和73 mW、谱宽32.3 nm和5.1 nm、脉宽22fs和33.3fs、重复率108 MHz的近红外和蓝光飞秒激光.整个系统具有结构紧凑、倍频效率高、运行稳定的特点.     

Characterization and modeling of a noncollinearly phase-matchedfemtosecond optical parametric oscillator based on KTA and operating tobeyond 4 μm

We describe the design and operation of a critically phase-matched femtosecond optical parametric oscillator based on KTA. By employing a small pump-signal noncollinear angle, tuning of the idler to beyond 4 μm is achieved using a Ti:sapphire pump laser. A Gaussian-beam model is described which can be used to identify the optimal noncollinear phase-matching geometry. Idler and signal pulses are characterized fully both temporally and spectrally and interferometric autocorrelation data at 3.5 μm showing idler pulses of only eight optical cycles duration are presented     

Femtosecond Cr/sup 4+/:YAG laser with 4 GHz pulse repetition rate

The construction of a compact, high-repetition-rate femtosecond Cr/sup 4+/:YAG laser is reported. Transform-limited pulses as short as 80 fs were generated at pulse repetition frequencies up to 4 GHz. The femtosecond pulses were tunable from centre wavelengths of 1505 to 1550 nm.     

Compact system of wavelength-tunable femtosecond soliton pulsegeneration using optical fibers

Using passively mode-locked femtosecond (fs) fiber laser and polarization maintaining fibers, the compact system of wavelength-tunable femtosecond (fs) fundamental soliton pulse generation is realized. The monocolored soliton pulse, not multicolored ones, with the ideal sech² shape is generated, and its wavelength can be linearly shifted by varying merely the fiber-input power in the wide wavelength region of 1.56-1.78 μm for a 75-m fiber. The soliton pulses of less than 200 fs are generated with the high conversion efficiency of 75%-85%. This system can be widely used as a portable and practical wavelength-tunable fs optical pulse sources     

掺钛蓝宝石飞秒激光空间光强分布特性的测量研究

为了更好地利用飞秒激光光源,采用自行设计的光束横截面空间光强分布测量装置研究了掺钛蓝宝石飞秒激光放大系统(美国光谱物理公司)输出的40 GW飞秒激光束的空间光强分布特性.通过对测量系统精确标定及对输出光束光强分布的研究表明:飞秒放大系统输出激光束在低泵浦电流下的光斑质量较好,在高泵浦电流下光斑质量变差,并且观察到了光束横截面中心区域的光强较低泵浦电流反而减小的情况,在多通放大过程中泵浦光的光斑质量对飞秒激光束空间分布有很大影响.     

Color center lasers passively mode locked by quantum wells

Using multiple-quantum-well (MQW) saturable absorbers, a NaCl color center was passively mode locked to produce 275-fs transform-limited, pedestal-free pulses with a peak power as high as 3.7 kW. The pulses are tunable from λ=1.59 to 1.7 μm by choosing MQWs with different bandgaps. The output pulses from the laser were shortened to 25 fs using the technique of soliton compression in a fiber. The steady-state operation of the laser requires the combination of a fast saturable absorber and gain saturation     

Broad-band diode-pumped ytterbium-doped fiber amplifier with 34-dBmoutput power

We investigate a high-power diode-pumped double-clad ytterbium-doped fiber amplifier with 34-dBm average output power and 1050-1095-nm bandwidth. A multidiode concentrator pumps the amplifier at 980 nm, with ~6 W of power launched into the inner cladding. Besides CW-signals, we amplify pulses from a mode-locked laser to 1 kW of peak power with only minor nonlinear distortions as well as pulses from a Q-switched laser to 50 μJ of energy. Reflections and backscatter limit the gain of the amplifier to 40 dB for a pump power of 2.5 W. For higher pump-powers than this, the amplifier started to self-Q-switch. The results are important for the development of cladding-pumped high-power fiber amplifiers