An efficient Schottky-varactor frequency multiplier at millimeter waves. Part III. Quadrupler

In this research the efficiency of a millimeter-wave Schottky-varactor quadrupler was studied. Theoretical simulations were carried out by using a nonlinear analysis program to find the optimum embedding impedances for a given diode. Emphasis was placed on the study of optimum idlers at the 2nd and 3rd harmonics, which are essential for a high quadrupling efficiency. For experimental verification a quadrupler for 140–155 GHz output frequency range with fixed idler terminations was constructed. This quadrupler was tested with different output configurations. A 10% tunable bandwidth was obtained with output power in the range of 1.5–2.7 mW whenP _in =40 mW. The highest efficiency measured was 11.3% at 148 GHz with 10 mW input power.     

High-efficiency longitudinally-pumped miniature Nd:YVO4 laser

We report on fundamental and intracavity frequency-doubled emission in a miniature Nd:YVO₄ (3×3×1 mm) laser. A maximum slope efficiency of η_s=58.6%, with optical efficiency of η₀=53.0% at 780 mW pump power was realized in a TEM₀₀ output beam. To obtain the optimum pump-beam focusing conditions we applied a new formalism in which the pump-beam propagation in the active medium was described by its M² factor. A good agreement between theoretical predictions and experimental results was observed. In second-harmonic regime, obtained by a KTP crystal, 230 mW green power that corresponds to 54% nonlinear conversion efficiency was reached.     

An efficient Schottky-varactor frequency multiplier at millimeter waves. Part I: Doubler

The efficiency of millimeter wave doublers with a wide tunable bandwidth was studied. The efficiency depends on the varactor parameters and the embedding impedances seen by the diode at fundamental and harmonic frequencies. Millimeter wave doublers were simulated with a nonlinear analysis program to find optimum embedding impedances for a given diode. Also the sensitivity of the efficiency to various diode and circuit parameters was evaluated. A scaled model was constructed in order to experimentally optimize the impedances. For experimental verification a doubler from 40–58 GHz to 80–116 GHz was constructed. The highest efficiency measured was 45% at 94 GHz with 5 mW input power. The highest efficiency obtained with 20 mW input power was 38%.     

An efficient Schottky-varactor frequency multiplier at millimeter waves. Part II: Tripler

The multiplication efficiency of millimeter wave triplers was studied. In the case of a commercially available Schottky-varactor, the tripler efficiency versus pump power, bias voltage, and embedding impedances at the fundamental and harmonic frequencies was simulated using a nonlinear analysis program. A scaled model of a waveguide mount was used to experimentally optimize the impedances. For experimental verification a tripler from 33–39 GHz to 99–117 GHz was constructed. The highest efficiency measured was 28% at 107 GHz with 5 mW input power. The highest efficiency obtained with 30 mW input power was 18%.     

Chip design of a 5.8-GHz fractional-N frequency synthesizer with a tunable Gm—C loop filter

This paper proposes a novel Gm-C loop filter instead of a conventional passive loop filter used in a phase-locked loop.The innovative advantage of the proposed architecture is tunable loop filter bandwidth and hence the process variations of passive elements of resistance R and capacitance C can be overcome and the chip area is greatly reduced.Furthermore,the MASH 1-1-1 sigma-delta(Σ▽) modulator is adopted for performing the fractional division number and hence improves the phase noise as well.Measured results show that the locked phase noise is 114.1 dBc/Hz with lower G m-C bandwidth and 111.7 dBm/C with higher G m-C bandwidth at 1 MHz offset from carrier of 5.68 GHz.Including pads and built-in Gm-C filter,the chip area of the proposed frequency synthesizer is 1.06 mm 2.The output power is 8.69 dBm at 5.68 GHz and consumes 56 mW with an off-chip buffer from 1.8-V supply voltage.     

Measured mixer noise temperature and conversion loss of a cryogenic Schottky diode mixer near 800 GHz

We accurately measured the noise temperature and conversion loss of a cryogenically cooled Schottky diode operating near 800 GHz, using the UCB/MPE Submillimeter Receiver at the James Clerk Maxwell Telescope. The receiver temperature was in the range of the best we now routinely measure, 3150 K (DSB). Without correcting for optical loss or IF mismatch, the raw measurements set upper limits ofT _M=2850 K andL _M=9.1 dB (DSB), constant over at least a 1 GHz IF band centered at 6.4 GHz with an LO frequency of 803 GHz. Correction for estimated optical coupling and mismatch effects yieldsT _M=1600 K andL _M=5.5 dB (DSB) for the mixer diode itself. These values indicate that our receiver noise temperature is dominated by the corner cube antenna's optical efficiency and by mixer noise, but not by conversion loss or IF mismatch. The small fractional IF bandwidth, measured mixer IF band flatness from 2 to 8 GHz, and similarly good receiver temperatures at other IF frequencies imply that these values are representative over a range of frequencies near 800 GHz.     

LD端面抽运c切Nd:YVO4自拉曼倍频589 nm黄光激光研究

报道了LD端面抽运c切Nd:YVO₄自拉曼倍频黄光激光器的研究. 采用10 mm长,二类临界相位匹配角 (θ=69°,ø=0°)切割的KTP晶体作为倍频晶体. 考虑到c切Nd:YVO₄跃迁截面较小,所以通过对谐振腔及晶体膜系的严格设计,减少腔内插入损耗和衍射损耗. 最终在脉冲重复率为10 kHz,抽运功率为11.2 W下,获得了最高570 mW的倍频黄光激光输出,对应抽运光到倍频黄光的转化效率约为 关键词： 拉曼激光 c切Nd:YVO₄')" href="#">c切Nd:YVO₄ 589 nm 黄光激光     

Nd:YVO4自受激拉曼激光器调Q锁模特性

利用Nd:YVO4激光晶体的自受激拉曼效应,结合Cr:YAG被动锁模技术和倍频技术,实现了结构紧凑的1176 nm和588 nm黄光锁模激光输出。激光器为LD端面泵浦,三镜折叠腔结构,并且采用了透过率为10%的输出镜。Nd:YVO4晶体长度为10 mm,Nd3+离子掺杂质量分数为0.2%,Cr:YAG晶体的初始透过率为67%。10 W激光泵浦时,1176 nm激光平均输出功率为123 mW,调Q包络宽度为6 ns,调Q包络内的锁模脉冲重复频率高达1 GHz。588.2 nm 黄光的平均输出功率为8 mW。     

CW and passive Q-switching of 1331-nm Nd:GGG laser with Co<Superscript>2+</Superscript>:LMA saturable absorber

In this paper, the output performances at 1331 nm in continuous-wave (CW) operation and the passive Q-switching regime of a Nd:Gd₃Ga₅O₁₂(Nd:GGG) laser crystal have been investigated under pumping with diode lasers. A maximum CW output power of 1.5 W was reached at an incident pump power of 7.5 W; the overall optical-to-optical efficiency and the slope efficiency with respect to the pump power were 21.5% and 19.4%, respectively. The passive Q-switching regime was achieved with Co²⁺:LaMgAl₁₁O₁₉ (Co²⁺:LMA) saturable absorber (SA) crystals. A maximum average output power of 183 mW was recorded with a Co²⁺:LMA SA with initial transmission T _i of 90%. The pulse energy was 18.7 μJ and the pulse duration was 26.1 ns, which correspond to a pulse peak power of 0.7 kW. With a Co²⁺:LMA SA with T _i=81%, the average power decreased to 131 mW. However, the pulse energy increased to 21.4 μJ, the pulse duration was 16.4 ns and the pulse peak power increased to 1.3 kW.     

Highly Efficient Frequency Doubling with a KNbO3 Semi-Monolithic Resonator

A semi-monolithic standing-wave resonator has been constructed and employed for frequency doubling of a Ti:sapphire laser. The resonator consists of a 5 mm long KNbO₃ crystal with dielectric coatings on both end faces and a spherical mirror with 20 mm radius of curvature. With 31.2 mW input power at 861.4 nm second harmonic power of 11.4 mW has been generated corresponding to the conversion efficiency of 36.5%.     

A frequency doubler for 200 GHz with a planar Schottky varactor

A frequency doubler for 200 GHz utilising a planar surface channel Schottky varactor was designed, constructed and tested. The doubler employes novel split-waveguide mount design with two sliding backshorts at both input and output waveguides. The theoretical maximum efficiency of the doubler is 44.0 % with input power level of 32 mW and the maximum output power is 16.5 mW with input power level of 50 mW. The measured maximum efficiency of the doubler was 7.1 % and the maximum output power was 2.6 mW     

Saturation recovery EPR and ELDOR at W-band for spin labels

A reference arm W-band (94 GHz) microwave bridge with two sample-irradiation arms for saturation recovery (SR) EPR and ELDOR experiments is described. Frequencies in each arm are derived from 2 GHz synthesizers that have a common time-base and are translated to 94 GHz in steps of 33 and 59 GHz. Intended applications are to nitroxide radical spin labels and spin probes in the liquid phase. An enabling technology is the use of a W-band loop-gap resonator (LGR) [J.W. Sidabras, R.R. Mett, W. Froncisz, T.G. Camenisch, J.R. Anderson, J.S. Hyde, Multipurpose EPR loop-gap resonator and cylindrical TE₀₁₁ cavity for aqueous samples at 94 GHz, Rev. Sci. Instrum. 78 (2007) 034701]. The high efficiency parameter (8.2 GW^−1/2 with sample) permits the saturating pump pulse level to be just 5 mW or less. Applications of SR EPR and ELDOR to the hydrophilic spin labels 3-carbamoyl-2,2,5,5-tetra-methyl-3-pyrroline-1-yloxyl (CTPO) and 2,2,6,6,-tetramethyl-4-piperidone-1-oxyl (TEMPONE) are described in detail. In the SR ELDOR experiment, nitrogen nuclear relaxation as well as Heisenberg exchange transfer saturation from pumped to observed hyperfine transitions. SR ELDOR was found to be an essential method for measurements of saturation transfer rates for small molecules such as TEMPONE. Free induction decay (FID) signals for small nitroxides at W-band are also reported. Results are compared with multifrequency measurements of T_1e previously reported for these molecules in the range of 2–35 GHz [J.S. Hyde, J.-J. Yin, W.K. Subczynski, T.G. Camenisch, J.J. Ratke, W. Froncisz, Spin label EPR T₁ values using saturation recovery from 2 to 35 GHz. J. Phys. Chem. B 108 (2004) 9524–9529]. The values of T_1e decrease at 94 GHz relative to values at 35 GHz.     

紧凑型LD端面抽运Nd:YAG内腔三倍频准连续355 nm紫外激光器

报道了一台LD端面抽运Nd:YAG晶体内腔三倍频355 nm激光高效率、高峰值功率准连续输出的全固态紫外激光器.激光腔采用紧凑型平平直腔,腔长仅106 mm.当注入抽运功率为5.73 W、重复频率为9 kHz时,获得163 mW的355 nm激光准连续输出,光光转换效率达到最高2.84％.当注入抽运功率为6.7 W重复频率为5 kHz时,获得最高174 mW的355 nm激光准连续输出,输出功率短期不稳定性为5％,光束质量因子M²为3.79.当注入抽运功率为5.73 W、重复频率为2 kHz时,获得112 mW的355 nm激光准连续输出,峰值功率最高达到9.15 kW.通过采用内腔倍频技术和设计合理的腔结构,实现了中小功率准连续输出的全固态紫外激光器的小型化、便携化,进一步拓宽了紫外激光器的应用领域. 关键词： LD端面抽运 内腔三倍频 Q')" href="#">声光调Q 紫外激光     

LD抽运Nd:LuVO4微片激光器性能研究

报道了一类新型的LD端面抽运Nd：LuVO₄微片激光器，讨论了在不同掺杂浓度，不同厚度和不同透过率下的激光性质，测定了在不同抽运功率下，微片最佳激光输出功率与LD抽运温度的关系.在2W抽运功率下获得923mW的1064nm激光输出，阈值为48mW，斜效率为52%.对微片制冷后斜效率提高到59%. 关键词： LD抽运 微片激光器 4')" href="#">Nd：LuVO₄     

8mm TE13 Mode Gyrotron

The design of a 8mm TE ₁₃ mode gyrotron is given in this paper. Discussions about the selection of the dimensions of the RF structure and electron gun are presented. Calculated results of the operating parameters of the gyrotron are also given. At 37.5GHz, pulse power 56kW is obtained for the gyrotron manufactured according to our design. Mode pattern obtained by scorching method shows that the mode of the output millimeter wave is TE ₁₃.     

Operation of a 32 GHz gyrotron

The design and operation of a 32 GHz pulsed gyrotron are reported. The device is step-tuned between the TE_1,2 (24.16 GHz) and TE_0,2 (31.78 GHz) modes with cathode voltages ranging from 30 to 40kV and beam current up to 5.0A. Experimental frequencies are in close agreement with the self-consistent calculated values and in the TE_2,2 resonator mode an output peak power of 6kW corresponding to an 18% efficiency was measured by using a fast response calorimeter with a thermal sensitivity of 0.1°C/Wmin.     

基于铱配合物材料的高效高稳定性有机发光二极管

使用基于重金属Ir的新磷光材料(tpbi)₂Ir(acac)，制备了多层结构有机发光二极管器件: ITO/CuPc (40 nm)/α-NPD (45 nm)/CBP: (tpbi)₂Ir(acac) (3%, 30nm)/BCP(20 nm)/Alq₃ (20 nm)/LiF (1 nm)/Al (100 nm).测试了材料的寿命、光谱吸收性质和器件的I-V-L特性.器件在低电压下电流符合热发射注入模型，高电压下I-V呈线形关系.不同偏压下器件发光光谱稳定，多峰拟合结果表明器件光谱由α-NPD发光峰(450 nm)，(tpbi)₂Ir(acac)主发光峰(518 nm)和肩峰(543 nm)构成.驱动电压为6 V时，器件效率达到最大12.1 lm/W，此时亮度为136 cd/m²，器件亮度最大为13500 cd/m²，此时效率为0.584 lm/W. 关键词： 有机发光二极管 磷光 效率 I-V-L特性')" href="#">I-V-L特性 光谱     

Spectroscopy,continuous-wave and <Emphasis Type="Italic">Q</Emphasis>-switched diode-pumped laser operation of Er<Superscript>3+</Superscript>,Yb<Superscript>3+</Superscript>:YVO<Subscript>4</Subscript> crystal

We report on the spectroscopy and, for the first time to our knowledge, continuous-wave and Q-switched diode-pumped laser operation of Er,Yb:YVO₄ crystal. Absorption and emission spectra of the crystal were determined. Lifetimes of Er^{3+ 4} I _13/2 and ⁴ I _11/2 levels that define laser performance of the crystal were measured and parameters of energy transfer between Yb³⁺ and Er³⁺ ions were estimated. cw output power of 115 mW with slope efficiency of 5.4% was achieved at 1604 nm. In the Q-switched mode an average output power of 81 mW with slope efficiency of 3.5% and pulse duration of 150 ns was obtained. In quasi-cw regime maximal peak power of 610 mW with slope efficiency of 6.7% was demonstrated. PACS 42.55.Xi; 42.60.Gd; 42.70.Hj     

Diode-pumped passively Q-switched Nd:LuxY1−xVO4 laser at 1.34 μm with two V:YAG saturable absorbers

Laser performance with the mixed Nd:Lu_0.15Y_0.85VO₄ crystal at 1.34 μm wavelength has been demonstrated. The continuous wave (cw) operation was carried out in a simple plano-concave resonator with an optical conversion efficiency of 23% and a slop efficiency of 25%. At a pump power of 6.78 W, the Q-switched pulses with the largest average output power of 349 mW, the shortest pulse width of 30.6 ns, the largest repetition rate of 42.5 kHz, the highest peak power of 268 W and the largest pulse energy of 8.2 μJ were obtained, corresponding to the V:YAG with initial transmission of 89%.     

Diode-pumped passively Q-switched intracavity frequency doubled Nd:GdVO4/KTP green laser

A compact diode-pumped passively Q-switched intracavity frequency-doubled Nd:GdVO₄/KTP green-pulse laser was demonstrated, using Cr⁴⁺:YAG as a saturable absorber in a simple flat–flat cavity. With a 5.9 W incident pump power, a passively Q-switched green laser was obtained with an average power of 397 mW, repetition rate of 40 kHz, and pulse width of 40 ns, when the initial transmission of Cr⁴⁺:YAG was 85%. The shortest pulse width of 30 ns, the highest green peak power of 696 W and the maximum pulse energy of 21 μJ were obtained when the initial transmission of Cr⁴⁺:YAG was 70%. Under CW green operation, we obtained 440 mW output power.