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1.
Abstract An AlGaAs/GaAs oxide‐stripe double‐heterostructure (DH) laser is fabricated by liquid‐phase epitaxy (LPE) successfully. This laser consists of four epilayers, i.e., (N) Al0.35Ga0.65As cladding layer, (p) Al0.05Ga0.95As active layer, (P) Al0.35Ga0.65As cladding layer and (p) Al0.05Ga0.95As contact layer, and a top SiO2 insulating layer. The stripe window opened through the SiO2 layer is either 5 or 10 μm wide. The emission properties of the laser diodes were all measured under pulse mode. The lowest threshold current measured is 95 mA for a 10, μm‐wide stripe laser which corresponds to a threshold current density of 3,200 A/cm2. The best power output is more than 30 mW per facet with a differential quantum efficiency of 10% per facet. In addition, the single filament operation is also observed in a 5 μm‐wide stripe laser. The lasing wavelength is centered around 8,500 Å. 相似文献
2.
《Fullerenes, Nanotubes and Carbon Nanostructures》2013,21(1-2):155-158
Abstract The method for the synthesis of fullerols C60(OH) x was developed, allowing to obtain products with low number of hydroxy groups attached to fullerene molecule. At the first stage, product C60(tert‐BuO) x was obtained by the radical reaction of C60 with tert‐butyl‐peroxide under heating or UV‐irradiation. At the second stage, fullerol C60(OH) x was synthesized after the elimination of tert‐butyl groups by acid treatment. Several samples C60(OH) x containing different numbers (x = 2–5) of hydroxy groups were obtained, the main product had x = 2. The structure of the fullerols was confirmed by UV‐ and Fourier‐transform infrared (FTIR)‐spectroscopy and MALDI‐TOF mass‐spectrometry. 相似文献
3.
Continuous wave and passively Q-switched laser operation with a mixed c-cut Nd:Gd0.33Lu0.33Y0.33VO4 crystal at 1.34 μm has been realized for the first time as far as we know. The largest output power of the continuous wave was 1.1 W for the output mirror of 5% transmission, with the optical conversion efficiency and the slope efficiency being 15% and 17.2%, respectively. The passive loss and the stimulated emission cross-section of the Nd:Gd0.33Lu0.33Y0.33VO4 crystal were found to be 0.6% and 0.47 × 10−19 cm2. The thermal lens effect that weakened the laser performance has also been measured. For passively Q-switched operation, the shortest pulse duration of 26 ns, the highest peak power of 1.8 kW, along with the pulse energy as large as 47 μJ, were obtained using V:YAG as Q-switch. The experimental results have shown that the passively Q-switched Nd:Gd0.33Lu0.33Y0.33VO4 laser can generate pulses with larger pulse energy and higher peak power in comparison with the passively Q-switched Nd:GdYVO4 lasers. 相似文献
4.
《Fullerenes, Nanotubes and Carbon Nanostructures》2013,21(1-2):147-154
Abstract The C60 complexes with decamethylcobaltocene: (Cp*2Co)2C60(C6H4Cl2, C6H5CN)2 (1) and [K · (18‐crown‐6)]2 · C60 · (DMF)4 (2) have been obtained as single crystals by the diffusion method. The IR‐ and UV‐VIS‐NIR‐spectra justify the formation of the C60 2? dianions in these salts. EPR measurements show that the low temperature signals of 1 in the 4–140 K range and 2 in the 4–60 K range have intensity corresponding only to 0.4% and 3.5% from total C60. Because of this, most of the complexes are EPR silent, and, consequently, C60 2? has a diamagnetic singlet (S = 0) state in these temperature ranges. The appearance of a broad EPR signal in the spectum of 1 above 140 K and 2 above ~60 K is assigned to a thermal population of a close lying excited triplet (S = 1) state. The singlet–triplet energy gap for C60 2? in solid 1 and 2 was estimated to be 730 ± 10 and 300 ± 10 cm?1. 相似文献
5.
《Fullerenes, Nanotubes and Carbon Nanostructures》2013,21(1-2):327-333
Abstract The results of investigation of the real and imaginary parts of third‐order nonlinear susceptibility (χ(3)) of C60 thin films (~100 nm) at the wavelength of Nd: YAG laser radiation (532 nm, τ = 55 ps) are presented using Z‐scan technique. Our studies show that the sign of Reχ(3) changes from negative, at pulse repetition rate of 2 Hz to positive, at 0.5 Hz. Sign variations of the real part of the third‐order susceptibility were attributed to the influence of the thermal lens. 相似文献
6.
We report the fabrication and operation of a single-to-three-mode, sub-nanosecond passively Q-switched Nd:Lu0.61Gd0.39VO4/Cr4+:YAG microchip laser, which exhibits changes in mode structure with increasing incident pump power. The laser exhibits longitudinal mode oscillations with a partial transverse mode overlap. The shortest pulse duration, highest pulse energy and peak power observed are 646 ps, 8.7 μJ and 13.5 kW, respectively. 相似文献
7.
Spectroscopic characterization of co-doped Tm,Ho:YVO4 crystal grown by the Czochralski method has been performed including absorption spectrum, emitting spectrum and luminescence decay lifetime. The polarization emitting spectrum around 2 μm is accomplished by exciting a singly Ho3+ doped YVO4 crystal to exclude the influence of Tm3+3F4-3H6 transition and the emission cross section is deduced from both Fuchtbauer-Ladenburg (F-L) equation and reciprocity method (RM). In addition, we report up to 10.4 W continuous wave (CW) output with a conversion efficiency of 40% and 10.3 W Q-Switch output with 12.5 kHz pulse repetition rate of diode-pumped cryogenic Tm,Ho:YVO4 laser. For Q-Switch operation, the minimum pulse width of 28.2 ns is obtained, all of which demonstrate that the Tm,Ho:YVO4 is excellent laser material for 2 μm radiation. 相似文献
8.
Vinh Quang Dang Tran Quang Trung Do‐Il Kim Le Thai Duy Byeong‐Ung Hwang Doo‐Won Lee Bo‐Yeong Kim Le Duc Toan Nae‐Eung Lee 《Small (Weinheim an der Bergstrasse, Germany)》2015,11(25):3054-3065
Ultraviolet (UV) photodetectors based on ZnO nanostructure/graphene (Gr) hybrid‐channel field‐effect transistors (FETs) are investigated under illumination at various incident photon intensities and wavelengths. The time‐dependent behaviors of hybrid‐channel FETs reveal a high sensitivity and selectivity toward the near‐UV region at the wavelength of 365 nm. The devices can operate at low voltage and show excellent selectivity, high responsivity (RI ), and high photoconductive gain (G). The change in the transfer characteristics of hybrid‐channel FETs under UV light illumination allows to detect both photovoltage and photocurrent. The shift of the Dirac point (V Dirac) observed during UV exposure leads to a clearer explanation of the response mechanism and carrier transport properties of Gr, and this phenomenon permits the calculation of electron concentration per UV power density transferred from ZnO nanorods and ZnO nanoparticles to Gr, which is 9 × 1010 and 4 × 1010 per mW, respectively. The maximum values of RI and G infer from the fitted curves of RI and G versus UV intensity are 3 × 105 A W?1 and 106, respectively. Therefore, the hybrid‐channel FETs studied herein can be used as UV sensing devices with high performance and low power consumption, opening up new opportunities for future optoelectronic devices. 相似文献
9.
Kaung‐Hsiung Wu 《中国工程学刊》2013,36(4):471-477
Abstract In this report, several methods have been provided to investigate the possibility of a long‐term sealed‐off operation of a CW transversely‐excited (TE) CO2 laser. These methods include the additions of molecular 3A sieve, CO gas, auxiliary discharge, and catalysts. Variations of gas composition, discharge voltage, and laser power under different conditions have been analyzed. SnO2 coating devices and monolithic catalysts have been introduced for the first time in a CW TE CO2 laser. With an appropriate amount of these catalysts, sealed‐off operation with an output level at 550W for more than 110 Hours of discharge time was achieved. 相似文献
10.
《Fullerenes, Nanotubes and Carbon Nanostructures》2013,21(1-2):175-179
Abstract Two new cavitands were prepared, their reactions with fullerene C60 afford novel complexes, hosting one and two C60 molecules. The cavitands were studied by solution NMR and solid‐state 13C, 29Si CP‐MAS NMR. The complexes obtained were characterized by elemental analysis, 13C and 29Si CP‐MAS NMR, UV and FTIR. In the complexes π–π, CH–π and n–π interactions were observed. 相似文献
11.
ABSTRACTWe demonstrate a pulse-duration tunable Tm3+-doped pulsed all-fiber master oscillator power amplifier (MOPA) operating at a central wavelength of 1908 nm. By using acousto-optic(AO) external modulation, the amplified laser pulse shows a tuning range having pulse durations from 66.5 ns to 8.0 μs and a repetition rate of 100 kHz-2 MHz. The laser achieved a maximum average power of 28.1 W and a corresponding energy of 28.1 μJ at 1MHz with a 3 dB linewidth of 0.63 nm and a beam quality factor of Mx2=1.25 and My2=1.32. The ASE suppression ratio is 50 dB and the corresponding total amplifier gain is 27.5 dB. To the best of our knowledge, it is the highest average output power and slope efficiency (~51.0%) achieved using AO external modulation in a Tm3+-doped pulsed fiber amplifier. 相似文献
12.
D. Pontiroli M. Riccò T. Shiroka M. Belli G. Ruani D. Palles 《Fullerenes, Nanotubes and Carbon Nanostructures》2013,21(2-3):391-400
Abstract The low‐doped Li x C60 compounds (x≤6) were investigated using laboratory X‐ray and synchrotron radiation diffraction, 13C NMR and Raman spectroscopy. Li4C60 shows an unusual 2D polymerisation in which the C60 units are connected both by [2+2] cycloaddition and by single carbon–carbon bonds, a unique feature among the known polymerised fullerene compounds. This picture is fully supported also by static NMR and Raman measurements. The charge transfer to C60 in the polymeric phase was evaluated from the shift of the Ag(2) mode. The depolymerisation process was investigated as well; despite the presence of two different bonds, the polymer‐to‐monomer transition induced by thermal treatments is a single‐step phenomenon. 相似文献
13.
J.T. Sroga J.C. Petheram M.S. Bowers R. Romea R.W. Lee 《Journal of Modern Optics》2013,60(11):2085-2100
Abstract Experimental measurements of the intra-pulse chirp and temporal coherence from a Joule class TE CO2 laser incorporating LAWS transmitter design features are presented. Digitized quadrature data (I and Q) from our ground-based coherent Doppler lidar system utilizing return signals off a hard target in the telescope far field are processed using fast Fourier transform and pulse pair techniques to obtain laser pulse frequency spectral components (offset frequency and spectral width) and high-resolution (~ 50 ns/sample) frequency chirp profiles. Less than 300 kHz of frequency chirp is observed in the first 3·5 μs of the laser pulse which contains approximately 90% of the pulse energy. Spectral width of the laser pulse, including both chirp and transform limited components, are measured to be less than 300 kHz full width at half maximum. 相似文献
14.
A. Nady M. H. M. Ahmed A. Numan S. Ramesh A. A. Latiff C. H. R. Ooi 《Journal of Modern Optics》2017,64(13):1315-1320
We demonstrate a Q-switched Erbium-doped fibre laser (EDFL) utilizing cobalt oxide (Co3O4) nanocubes film based saturable absorber (SA) as a passive Q-switcher. Co3O4 nanocubes are embedded into a polyethylene oxide film to produce a high nonlinear optical response, which is useful for SA application. It has saturation intensity and modulation depth of 3 MW/cm2 and 0.35%, respectively. The proposed laser cavity successfully generates a stable pulse train where the pulse repetition rate is tunable from 29.8 to 70.92 kHz and the pulse-width reduces from 10.9 to 5.02 μs as the 980 nm pump power increases. This result indicates that the Co3O4 is excellent for constructing an SA that can be used in producing a passively Q-switched fibre laser operating at a low pump intensity. To the best of our knowledge, this is the first demonstration of Co3O4 film based fibre laser. 相似文献
15.
Ahmed Shakir Al-Hiti A. H. H. Al-Masoodi H. Arof Wei Ru Wong 《Journal of Modern Optics》2020,67(4):374-382
ABSTRACTThis paper reports a new type of passive saturable absorber (SA) made of transition metal oxide (TMO) embedded in polyvinyl alcohol (PVA). The Tungsten trioxide (WO3)-PVA SA is placed in an erbium-doped fibre laser cavity to produce Q-switched pulses operating at 1562.82?nm. The pulse laser starts to manifest at the threshold pump power of 40?mW and continues to exist until the maximum pump power of 195?mW. Within that pump power range, its pulse energy, repetition rate and pulse width vary from 98 to 142.85?nJ, 29.86 to 56.7?kHz and 5.032 to 1.85?µs, respectively. The pulse train is stable with a signal to noise ratio of 70?dB. This is the first demonstration of a Q-switched laser using such a SA. 相似文献
16.
A. V. Semeno A. A. Pronin N. E. Sluchanko N. A. Samarin A. V. Kuznetsov S. V. Demishev 《Journal of Superconductivity and Novel Magnetism》2007,20(2):109-112
Electron spin resonance of a single crystal of CuGeO3 doped with 2% of Co has been studied at f = 99 GHz in temperature range 1.8–50 K. Contributions to ESR absorption from Cu2+ chains and from Co2+ ions were derived. It is found that functions obtained for ESR integrated intensities: Curie-Weiss for Cu2+ (χCu ∼ C
Cu/(T + Θ), with Θ = 92 K) and Curie for Co2+ (χCo ∼ C
Co/T) are well consistent with temperature dependence of static magnetic susceptibility. Strong dependence of ESR absorption on
polarization of oscillating magnetic field was discovered for Co2+ contribution. Polarization effect was studied for magnetic field applied along a, b and c directions. Values of g-factors of resonance lines are presented. 相似文献
17.
Intense 2.7 μm emission from Er3+ doped in a new type of ZrF4-based fluoride glass is reported. 2.7 μm emission characteristics and energy transfer process upon excitation of a conventional 980 nm laser diode are investigated. Based on the absorption spectra, the Judd-Ofelt parameters and radiative properties were calculated and compared with those of other glass hosts. The prepared glass possesses higher predicted spontaneous transition probability (29.04 s−1) along with larger calculated emission cross section (9.16 × 10−21 cm2). Besides, the energy transfer coefficient of laser upper level (4I11/2) can reach as high as 6.56 × 10−39 cm6/s. Hence, these results indicate that this Er3+ doped ZrF4-based fluoride glass has potential applications in 2.7 μm laser. 相似文献
18.
B.T. Zhang H.T. Huang J.L. He J.F. Yang J.L. Xu C.H. Zuo S. Zhao 《Optical Materials》2009,31(11):1697-1700
In this paper, the output performances at 1.34 μm in continuous wave operation and passive Q-switching regime of a diode-end-pumped Nd:Gd0.5Y0.5VO4 laser have been investigated. The passive Q-switching regime was achieved with Co2+:LaMgAl11O19 (Co2+:LMA) saturable absorbers crystals. A maximum average output power of 230 mW was recorded with a Co2+:LMA with initial transmission of 81%. The minimum pulse duration was 116 ns, which corresponded to a repetition rate of 360 kHz, the single pulse energy of 2.1 μJ and the pulse peak power of 5.5 W. 相似文献
19.
《Materials Science & Technology》2013,29(10):1232-1238
AbstractMultisheet structure of Inconel 718 superalloy will be widely used in vehicles as heat resisting and heat shielding structure due to its lightweight, high strength and stiffness. Multisheet structure of Inconel 718 superalloy was processed by laser beam welding and superplastic forming (LBW/SPF) technology in the present paper. Multisheet structure of Inconel718 superalloy processed by LBW/SPF technology exhibits good configuration and uniform thickness distribution. Laser beam welding parameters for multisheet structure were as follows: pulse frequency was 32 Hz; pulse duration 3 ms; peak power per pulse 4500 W; welding speed 180 mm min–1; SPF parameters were as follows: temperature Tf=965°C; forming pressure P f=4·2 MPa; forming time t f=130 min. Microstructure of multisheet structure was studied carefully. Microstructure in weld fusion zone was constituted of austenite dendritics and Laves phase precipitated in interdendritics. After SPF process, austenite dendritics in the weld fusion became coarser and most of Laves phases were dissolved and turned into δ precipitated phase but a few of Laves phases were still reserved. And Nb concentration in dendritics increased to 5·42% compared to 2·82% under as welded condition. Weld metal hardness increased from 331·63 under as welded condition to 391·74 under post-SPF condition which was closed to the base material hardness of post-SPF. Grain size of base material grew slightly and an amount of precipitated phase appeared in the base material undergoing SPF process. The tensile test results of base material show that tensile strength increased obviously and the ductility decreased slightly after SPF process. Therefore, LBW/SPF technology is an appropriate forming technique for multisheet structure of Inconel 718 superalloy. 相似文献
20.
V. P. Danilov B. I. Denker V. I. Zhekov D. I. Murin T. M. Murina S. V. Sverchkov M. I. Studenikin 《Technical Physics Letters》2006,32(2):156-157
A pulse laser on a phosphate glass activated by Cr3+-Yb3+-Er3+ ions (λ = 1.54 μm) was used to pump Y2Al5O12:Er3+ (YAG:Er) crystals to the lower laser level of a 3-μm transition (4I11/2 → 4I13/2) in Er3+ ions (λ = 2.94 μm). For a pumping pulse energy of E exc = 200 mJ, the efficiency of 3-μm lasing was 20%. A differential efficiency of the YAG:Er laser in the case of a resonance pumping into the lower laser level amounted to 26%. 相似文献