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1.
Near-keV coherent X-ray generation with sub-10-fs lasers 总被引:1,自引:0,他引:1
Spielmann C. Kan C. Burnett N.H. Brabec T. Geissler M. Scrinzi A. Schnurer M. Krausz F. 《IEEE journal of selected topics in quantum electronics》1998,4(2):249-265
Recent advances in solid-state laser technology and ultrafast optics have led to the generation of optical pulses as short as 5 fs with peak powers up to 0.1 TW from a compact kilohertz-repetition-rate all-solid-state laser. This source significantly pushes the frontiers of nonlinear optics. Intriguing possibilities include the development of a compact laser-driven coherent soft-X-ray source at photon energies near 1 keV, and the generation of autosecond XUV pulses. This paper analyzes strong-field ionization and high-harmonic generation in the few-cycle regime, and reviews the first experimental realization of high-harmonic generation with 5-fs pulses. These experiments have resulted in the emission of coherent X-rays at photon energies greater than 0.5 keV (λ<2.5 nm), representing the highest photon energies achieved with a laser-driven coherent source so far. The generated XUV beam is well collimated and predicted to be delivered, after suitable spectral filtering, in a single burst of autosecond duration 相似文献
2.
Kim H.T. Kim I.J. Tosa V. Kim C.M. Park J.J. Lee Y.S. Bartnik A. Fiedorowicz H. Nam C.H. 《IEEE journal of selected topics in quantum electronics》2004,10(6):1329-1338
We have performed the optimization of high-order harmonic brightness from long gas jets by using self-guided and chirped femtosecond laser pulses and analyzed their coherence properties. The characteristics of laser pulse propagation were analyzed both in theory and in experiments to understand the self-guiding process of laser pulses and chirp compensation mechanism. Highly efficient harmonic generation with low beam divergence and narrow bandwidth was achieved by applying these two techniques to the long gas jets. The coherence properties of the bright harmonics were examined using double-pinhole interference and spectral interference. 相似文献
3.
Anandarajah P.M. Guignard C. Clarke A. Reid D. Rensing M. Barry L.P. Edvell G. Harvey J.D. 《IEEE journal of selected topics in quantum electronics》2006,12(2):255-264
In this paper, we demonstrate the generation of transform-limited short optical pulses, which display excellent spectral and temporal qualities by employing a novel technology, based on an externally injected gain-switched laser in conjunction with a nonlinearly chirped grating. Using this technique, 3.5-ps optical pulses exhibiting a time-bandwidth product (TBP) of 0.45 are generated, which are suitable for use in high-speed 80 Gb/s optical time-division multiplexing (OTDM) communications systems. The numerical integration of a set of rate equations using suitable parameters for the devices used in the experiments were carried out to further confirm the feasibility of the proposed method for developing an optimized pulse source for high-speed photonic systems. 相似文献
4.
The principal ideas of the thin-disk laser design will be illustrated and the advantages for operating different laser materials will be explained. The results for continuous-wave (CW) and Q-switched operation as well as for amplification of short (nanosecond) and ultrashort (picosecond, femtosecond) pulses demonstrate the potential of the thin-disk laser design. The scaling laws for this laser design show that the power limit for CW operation is far beyond 40 kW for one single disk and the energy limit is higher than 3 J from one disk in pulsed operation. Also, the applicability of the thin-disk laser concept to optically pumped semiconductor structures will be discussed. When pumping directly into the quantum wells, the energy defect between the pump photon and the laser photon can be smaller than 5%, thus reducing the waste heat generated inside the semiconductor structure. First results demonstrate the potential of this new concept. Finally, a short overview of the industrial realization of the thin-disk laser technology will be given. 相似文献
5.
Xudong Jiang Itzler M.A. Ben-Michael R. Slomkowski K. 《IEEE journal of selected topics in quantum electronics》2007,13(4):895-905
In this paper, we describe the design, characterization, and modeling of InGaAsP/InP avalanche diodes designed for single photon detection at wavelengths of 1.55 and 1.06 mum. Through experimental and theoretical work, we investigate critical performance parameters of these single photon avalanche diodes (SPADs), including dark count rate (DCR), photon detection efficiency (PDE), and afterpulsing. The models developed for the simulation of device performance provide good agreement with experimental results for all parameters studied. For 1.55-mum SPADs, we report the relationship between DCR and PDE for gated mode operation under a variety of operating conditions. We also describe in detail the dependence of afterpulsing effects on numerous operating conditions, and in particular, we demonstrate and explain a universal functional form that describes the dependence of DCR on hold-off time at any temperature. For 1.06-mum SPADs, we present the experimentally determined relationship between DCR and detection efficiency for free-running operation, as well as simulations complementing the experimental data. 相似文献
6.
Kalashnikov M.P. Osvay K. Lachko I.M. Schonnagel H. Sandner W. 《IEEE journal of selected topics in quantum electronics》2006,12(2):194-200
It is experimentally proved that successive amplification of negatively and positively chirped laser pulses (NPCPA) counteracts the gain narrowing effect typical in chirped pulse amplification (CPA) lasers. The scheme is robust and easy to adopt to even petawatt (PW) level high power laser systems. As a demonstration, a multi-terawatt (TW) Ti:sapphire laser system was modified to the NPCPA. The bandwidth of the 150 mJ output pulses exceeds 50 nm without any additional spectral correction, which is 30% broader than those currently available from conventional CPA lasers. Moreover, the NPCPA scheme gives an opportunity to increase an intensity temporal contrast without any compromise in pulse energy. 相似文献
7.
Dubietis A. Butkus R. Piskarskas A.P. 《IEEE journal of selected topics in quantum electronics》2006,12(2):163-172
Since the proof-of-principle demonstration of optical parametric amplifier to efficiently amplify chirped pulses in 1992, optical parametric chirped pulse amplification (OPCPA) became a widely recognized and rapidly developing technique for high-power femtosecond pulse generation. In the meantime, we are witnessing an exciting progress in the development of powerful and ultrashort pulse laser systems that employ chirped pulse parametric amplifiers. These systems cover a broad class of femtosecond lasers, with output power ranging from a few gigawatts to hundreds of terawatts, with a potential of generating few-optical-cycle pulses at the petawatt power level. In this paper, we discuss the main issues of optical parametric chirped pulse amplification and overview recent progress in the field. 相似文献
8.
Agnesi A. Dell'Acqua S. Morello C. Piccinno G. Reali G.C. Zhaoyang Sun 《IEEE journal of selected topics in quantum electronics》1997,3(1):45-52
We report on the experimental results of a continuously diode-laser pumped Nd:YAG laser, operating at 1064 nm and repetitively Q-switched by a Cr4+:YAG solid-state saturable absorber. End-pumping the Nd:YAG with a 10-W fiber-coupled diode-laser we could either optimize the energy or the average output power, depending on the choice of the saturable absorber and the output coupler. The maximum energy was ≈200 μJ in single TEM00, 17 ns pulses at 6 kHz, whereas a maximum average power of ≈2 W with 32-ns pulses at 20 kHz was obtained. We also present preliminary results of a repetitively Q-switched Nd:YVO4 laser at 1064 nm. The repetitive Q-switching operation is described by an improved model, which accounts for the behavior of both the active medium and the solid-state saturable absorber. The results of the model agree fairly well with the experimental data. Experimental results of second harmonic conversion are also reported and interpreted using a depleted pump model 相似文献
9.
For pt.I see ibid., vol.2, no.4, p.847-60 (1996) We investigated the transmission, scattering, and reflection of plasmas produced in water by Nd:YAG laser pulses of 6-ns and 30-ps duration. The transmission measurements comprise a large energy range at wavelengths of 1064 and 532 nm and various focusing angles between 1.7° and 22°. This parameter range covers the parameters used for intraocular microsurgery, but also allows one to assess the influence of self-focusing on plasma shielding, which is only relevant at small focusing angles. We found that most of the laser light is either absorbed or transmitted; scattering and reflection amount to only a few percent of the incident laser energy. The transmission is considerably higher for picosecond pulses than for nanosecond pulses, regardless of the focusing angle. The plasma transmission increases with decreasing focusing angle. Self-focusing, which occurs at focusing angles below 2°, leads to a further increase of transmission. The experimental results were compared with the predictions of the moving breakdown distributed shielding model. Only partial agreement could be achieved, because the model assumes a spatially and temporally constant absorption coefficient within the plasma which is not realistic. The model can, however, be used to determine the average absorption coefficient. Fits of calculated transmission curves to the experimental data at &thetas;=22° yielded 900 cm-1⩽α⩽1800 cm-1 nanosecond plasmas and 360 cm-1⩽α⩽570 cm-1 picosecond plasmas. The efficacy of plasma-mediated intraocular laser surgery is higher with 6-ns pulses than with 30-ps pulses, because with the nanosecond pulses nearly 50% of the laser pulse energy is absorbed already at threshold, whereas it is only 8% with the picosecond pulses 相似文献
10.
《IEEE journal of selected topics in quantum electronics》2009,15(6):1581-1590
11.
Arahira S. Kutsuzawa S. Matsui Y. Ogawa Y. 《IEEE journal of selected topics in quantum electronics》1996,2(3):480-486
Higher order chirp compensation of optical short pulses by using two types of optical fibers with different group-velocity dispersions was theoretically and experimentally investigated in detail. By optimizing the lengths of two types of optical fibers, both second- and third-order dispersion of chirped optical pulses were found to be simultaneously compensated. Pulse-compression experiments with chirped optical pulses from a mode-locked laser diode demonstrated using this technique attained nearly transform-limited, 500-fs pulse generation 相似文献
12.
Kyungbum Kim Shinwook Lee Delfyett P.J. 《IEEE journal of selected topics in quantum electronics》2006,12(2):245-254
In this paper, we propose a novel method, called "eXtreme chirped pulse amplification (X-CPA)," to overcome the fundamental energy storage limit of a semiconductor optical amplifier. The method is studied numerically and experimentally. Based on the X-CPA concept, 1.4-kW record peak power is generated from an all-semiconductor X-CPA system. Prior to an extreme pulse compression stage, greater than microjoules output energies of 20 ns extremely stretched pulses are extracted from a flared semiconductor optical amplifier. 相似文献
13.
Q-Han Park Boyd R.W. Sipe J.E. Gaeta A.L. 《IEEE journal of selected topics in quantum electronics》2002,8(3):413-417
We present a theoretical model of optical harmonic generation excited by laser beams sufficiently intense that relativistic effects are important. This model shows that, under relativistic conditions, third-harmonic generation can be excited with comparable efficiency by either linear or circularly polarized light. This result is to be contrasted with experience from traditional (nonrelativistic) nonlinear optics, where group-theoretical arguments show that third-harmonic emission cannot occur under circularly polarized excitation. These results are in good agreement with the observed polarization dependence of the third-harmonic emission reported recently in an experiment conducted under conditions such that relativistic effects are important. Our theoretical model also predicts that all even and odd harmonies of the fundamental laser frequency are emitted in the near-forward direction with an intensity that increases with that of the incident laser field 相似文献
14.
Tm-Doped Fiber Lasers: Fundamentals and Power Scaling 总被引:2,自引:0,他引:2
《IEEE journal of selected topics in quantum electronics》2009,15(1):85-92
15.
Furst C. Leitenstorfer A. Laubereau A. 《IEEE journal of selected topics in quantum electronics》1996,2(3):473-479
An experimental and theoretical analysis of the nonlinear coupling mechanism between the two solitary pulses circulating in a two-color femtosecond laser is presented. Two operation regimes; synchronized; and nonsynchronized; and a hysteresis of the transition between the two regimes are clearly observed; while independent modelocking and tunability of the output pulse trains is found in both regimes. Pulses in the range from 15 to 100 fs are synchronized with a timing jitter below 2 fs. The combined effects of cross-phase modulation and negative group velocity dispersion are shown to be responsible for the strong pulse correlation in the synchronized regime. Our experimental observations are in agreement with numerical simulations, thus confirming the theoretical model 相似文献
16.
Soliton mode-locking with saturable absorbers 总被引:2,自引:0,他引:2
Kartner F.X. Jung I.D. Keller U. 《IEEE journal of selected topics in quantum electronics》1996,2(3):540-556
We investigate ultrashort pulse generation based on the fundamental soliton generation that is stabilized by a saturable absorber. The case of an absorber with a recovery time much longer than the pulsewidth of the generated soliton is investigated in detail. Based on soliton perturbation theory we derive equations for the soliton variables and the continuum generated in a mode-locked laser. Analytic criteria for the transition from stable to unstable soliton generation are derived. The results demonstrate the possibility of ultrashort pulse generation by a slow saturable absorber only. The theoretical results are compared with experiments. We generate pulses as short as 13 fs using only semiconductor saturable absorbers 相似文献
17.
Mathematical modeling is used to estimate the performances of the three-micron Er:YAG laser in various generation regimes. The model, based on simple rate equations, uses exclusively spectroscopic data and includes upconversion from both initial (/sup 4/I/sub 11/2/) and terminal (/sup 4/I/sub 13/2/) levels as well as the cross-relaxation from the pump level (/sup 4/S/sub 3/2/). Despite the unfavorable ratio between the lifetimes of the laser levels, the recirculation of the excitation on the metastable levels produced by the effective energy transfer processes at high erbium concentrations leads to rather high emission efficiency in the continuous wave (CW) regime. In contrast, in the Q-switch regime, the energy transfer processes are practically frozen during the giant pulse generation and the access to the stored energy is limited. In this paper, simple analytical expressions for emission efficiency in CW and Q-switch regimes are presented. Due to the growing interest in short laser pulses for medical applications, we discuss in more detail the Q-switch regime (pump conditions, co-doping, etc.). 相似文献
18.
Kurdi G. Osvay K. Csatari M. Ross I.N. Klebniczki J. 《IEEE journal of selected topics in quantum electronics》2004,10(6):1259-1267
Broad-band amplification of femtosecond laser pulses using the scheme of noncollinear optical chirped pulse parametric amplification is modeled. The effect of two-photon absorption at the pump wavelength was also taken into account. The signal pulses range from 220 to 410 nm with pump pulses at 267, 248, and 213 nm. The best four crystals chosen among 12 possible ones are BBO, KDP, CLBO, and LB4. In an experiment, 30-fs laser pulses at 400 nm were amplified in a BBO crystal pumped by 267 nm pulses, exhibiting a single pass gain of 3550. The gain was found spectrally flat within the available 17-nm bandwidth of the signal pulse. 相似文献
19.
20.
We describe the use of a computational method for determining the overlap distance minimizing the mutual interaction between
two adjacent coils that constitute a part of a phased array system used in MRI. The method is based upon the method of moments,
and the analysis is carried out at a target imaging frequency to obtain the overlap distance. For a variety of complex RF
phased array coils, we can determine, using the proposed approach, the overlap distance between nearest neighbor block element
RF coils such that the mutual interaction is nullified or minimized. We give experimental results to validate the proposed
approach. When compared with the experimental data, our theoretical prediction is in excellent agreement. 相似文献