Three-Wave Trapponic Solitons for Tunable High-Repetition Rate Pulse Train Generation

We demonstrate that the parametric mixing of an ultrashort Zakharov-Manakov (ZM) soliton pulse with a quasi-continuous-wave (CW) signal in a weakly quadratic nonlinear and dispersive medium may lead to the generation of a three-wave soliton with variable speed, or trappon. We show that trappons may provide a novel mechanism of cavityless ultrashort pulse train generation. The timewidth, the amplitude and the repetition rate of the generated pulse trains may be controlled in a stable manner by adjusting the intensity level of the CW signal and/or the ZM short soliton pulse.     

Optical parametric interactions in 3-methyl-4-nitropyridine-1-oxide (POM) single crystals

Various configurations of three-wave parametric interactions are reported at the picosecond time scale, in 3-methyl-4-nitropyridine-1-oxide (POM) single crystals. Wavelength dispersion of phase-matched second-harmonic generation orientation is experimentally established within the0.8-2 mum range using as fundamental input the idler and signal emissions of a picosecond LiIO3parametric emitter. Efficient parametric amplification is demonstrated: at degeneracy a gain of 10³is measured for a pump intensity of 130 MW . cm^-2at 0.53 μm and an input signal of 5 kW . cm^-2at 1.06 μm. Single pass parametric emission is achieved, for the first time in an organic crystal, yielding 200 kW . cm^-2at 1.06 μm, using the frequency-doubled output of a passively mode-locked YAG system. Both dispersion and interaction length dependence of the experimental gain are accounted for.     

Resonantly enhanced 26 GHz parametric upconversion of CO2laser in NH3

Resonantly enhanced three-wave mixing of the 10.784 μmR(18) line of the C¹³O2¹⁶laser and microwave radiation at 26.378 GHz in Stark tunable N¹⁴H3has resulted in upconverted parametric output at 10.774 μm. The energy levels of N¹⁴H3involved in the interaction and the apparatus used in the experiment are described. Experimental results showing saturation of the parametric signal with increasing N¹⁴H3pressure, input microwave power, and input laser power are described.     

Phase-conjugate pump dithering for high-quality idler generation in a fiber optical parametric amplifier

We experimentally demonstrate a simple technique to cancel the idler broadening in a fiber optical parametric amplifier (OPA) by using two pumps phase-modulated 180/spl deg/ out of phase, one of them being obtained by four-wave mixing in an auxiliary fiber. The resulting OPA idler quality is comparable to that of the output signal.     

参数化VSAR运动目标检测和定位研究进展

针对速度合成孔径雷达（VSAR）地面运动目标检测和定位，给出参数化VSAR的若干研究进展。首先，建立由目标、多普勒分布式杂波和噪声组成的参数化VSAR统计信号模型。其次，提出自适应最优处理实现运动目标检测，提高了非均匀杂波背景中的目标检测性能。第三，基于最大似然方法和克拉美一罗界分析参数估计和目标定位的极限性能。第四，讨论基于多视处理对目标检测和定位可能的性能改善。最后，数值仿真结果证明了参数化VSAR在运动目标检测和定位方面的有效性和优越性能。     

FSK Coherent Demodulation Using Second- Harmonic Injection Locked Oscillator

We present an alternative coherent demodulation of frequency shift keying (FSK) signals based on the use of a super harmonic injection locked oscillator (ILO). Demodulation consists of multiplying the incoming FSK signal by the output of the ILO using an up-conversion mixer. The product includes a second harmonic signal that locks the oscillator, closing a non-linear feedback loop, and synchronizes its output with the incoming FSK signal. In addition to the second harmonic, the product also includes a base band signal that reproduces the original modulation. We built and tested a hybrid prototype of the demodulation system for the frequency range from 250 to 300 MHz. The circuit consists of a second-harmonic differential output ILO with varactor diodes as tuning elements and a four quadrant analog multiplier. Our results demonstrate the reliability and robustness of the demodulator system.      

Coherent detection of stimulated Brillouin backscatter on photoconductive three-wave mixer for sensing applications

Describes the coherent detection of stimulated Brillouin scattering (SBS) from an optical fibre, using an InP photoconductive three-wave mixer. In this mixer two optical signals offset by 33 GHz are multiplied together with a microwave signal, all within the same device, to produce an output signal of a few hundred MHz. This arrangement could be used to measure the temperature distribution along a fibre.<>     

A simultaneously phase-matched tandem optical parametric oscillator

We report the theoretical analysis of a simultaneously phase-matched tandem optical parametric oscillator (STOPO) in which the principal OPO generates a signal which pumps a secondary OPO. Both OPO interactions are assumed to be phase-matched in a single crystal. The cavity has high Q for the signal produced by the principal OPO and has lower Q for the signal of the secondary OPO. The pump and the two idler frequencies are not resonated. The five waves undergoing nonlinear mixing are assumed to be nondegenerate in either frequency or polarization. We show that the useful output, consisting of the two idlers and the signal of the secondary OPO, can be produced with high efficiency over a large dynamic range in the pump intensity. We discuss the tuning with temperature and grating period of a STOPO based on periodically poled LiNbO₃ pumped at 1.064 μm. We present results based on both plane-wave modeling and modeling in three spatial dimensions     

Narrow-linewidth idler generation in fiber four-wave mixing andparametric amplification by dithering two pumps in opposition of phase

Wide-bandwidth and high-gain fiber optical parametric amplifiers (OPAs) have been demonstrated recently. Their application as all-optical wavelength converters has been hampered by pump-induced converted-signal spectrum broadening, due to the required pump phase modulation. In this paper, we theoretically investigate and experimentally demonstrate a technique to cancel the converted-signal broadening by using four-wave mixing (FWM) or parametric amplification with two pumps phase-modulated 180° out of phase. The resulting converted-signal quality is comparable to that of the output signal     

A broadly tunable wavelength-selectable WDM source using a fiberSagnac loop filter

In this letter, we describe a new discretely wavelength-selectable 1.5-μm source based on the use of a fiber Sagnac loop filter leading to the possibility of an efficient all-fiber source. The filter has an ~1.6-dB insertion loss, 14-dB peak-to-valley transmission ratios, and can be tuned to a very precise match with the International Telecommunications Union-wavelength-division-multiplexing grid. We demonstrate 25-channel outputs with precise 50-GHz channel spacings and very large (65 dB) output signal to background noise ratios     

Superconductor-to-Semiconductor Interface Circuit for High Data Rates

We present a new kind of rapid-single-flux-quantum (RSFQ) output driver together with a pseudomorphic high electron mobility transistor (p-HEMT) amplifier both operating at liquid helium temperature. The passive interconnect including the interchip connection between the RSFQ output driver and the first transistor stage of the semiconductor amplifier is the key element for signal matching and was optimized for minimizing the reflections to the RSFQ circuit. The RSFQ output driver is based on a single-flux-quantum to dc converter and a voltage doubler. The circuit is realized in the Niobium based 1 kA/cm$^{2}$ process of FLUXONICS Foundry and provides up to 438-$mu$V output voltage. We demonstrate high-speed experiments of the output driver in combination with two different semiconductor amplifier circuits at liquid helium temperature. The output voltage of a 2-Gb/s data stream was measured to be about 3.5 mV.      

A multiwavelength short pulse source based on saturated optical fiber parametric amplification

We describe a 10-GHz multiwavelength pulse source based on high-order four-wave mixing products generated by a saturated optical fiber parametric amplifier. We employ a nonlinear modulation scheme for the pump which plays two roles. First, it enables us to use a high pump power with no phase modulation, and second, it yields narrow (6 ps) pulses with a constant spectral width and the same jitter level (/spl sim/150 fs) for the signal and three idler wavelengths.     

Experimental study on all-optical half-adder based on semiconductor optical amplifier

We demonstrate a novel all-optical haft-adder based on two semiconductor optical amplifiers （SOAs）. Two optical bandpass filters are used to select the two idlers generated by four-wave mixing （FWM） effect of the first SOA. Therefore, the AND gate and XNOR logic are realized simultaneously. The second SOA acts as a NOT gate, in which the NOR logic is achieved with the input of the logic XNOR. As a result, the output is the sum of the two input bits and the carry. In the experiment, all-optical haft-addition calculation is achieved between two 10 Gb/s signals.     

The tandem optical parametric oscillator

We report the theoretical analysis of a tandem optical parametric oscillator (TOPO) in which the principal OPO generates a signal which pumps a secondary OPO. The signal produced by the principal OPO is resonated in a high-Q cavity containing both nonlinear crystals. This cavity also has low Q for the signal of the secondary OPO. The two OPO's are singly resonant, since neither idler is resonated. We show that the useful output, consisting of the two idlers and the signal of the secondary OPO, can be produced with high efficiency over a large dynamic range in the pump intensity. As an example, we discuss modeling in three space dimensions of a Nd:YAG-pumped monolithic TOPO based on periodically poled LiNbO₃. This TOPO could generate three infrared wavelengths in high-transmission bands of atmospheric water vapor     

New simple square-rooting circuits based on translinear current conveyors

Two new square-rooting circuits, based on second-generation current-controlled current conveyors (CCCIIs), are presented. The first square-rooting circuit consists of two CCCIIs, one current-controlled resistor and two grounded resistors. The input signal of the first circuit is a voltage, and output is the voltage proportional to the square root of input voltage. The second one consists of two CCCIIs and a current-controlled resistor. In the second circuit, the input signal is a current, and output is the current proportional to the square root of input current. Each circuit realizes by using a current-mode technique; hence the proposed square-rooting circuits are simple circuitry, wide dynamic range and wide bandwidth. The proposed square-rooting circuits were confirmed by using PSPICE simulation.     

Optical level equalisation based on gain saturation in fibreoptical parametric amplifier

Optical level equalisation operation based on gain saturation in an optical fibre parametric amplifier is reported. The signal output has been measured as a function of the signal input in a fibre parametric amplifier, with the result that the signal gain saturates as the input power increases and the output power reached a maximum value at a particular input level. Utilising this gain saturation property, optical level equalisation has been demonstrated     

周期极化掺镁铌酸锂光参量振荡器的输出光谱特性

实验研究了基于多周期的掺镁铌酸锂晶体光参量振荡器(OPO),分析了光学参量振荡器的输出光谱特性.实验中,采用激光二极管(LD)端面抽运的声光调Q Nd:YVO4激光器作为光参量振荡器的抽运源,谐振腔采用双凹腔结构.在调Q开关重复频率为10 kHz,周期极化掺镁铌酸锂(PPMgLN)晶体的温度为25.4℃的条件下,实验测得光学参量振荡器的振荡阈值为110 mW.当输入的抽运光的平均功率为325 mW时,获得了平均功率为84 mW的信号光输出,其光-光转换效率为25.8%.通过改变周期极化掺镁铌酸锂晶体的温度(25.4～120℃)和极化周期(28.5～30.5 μm),实现了信号光在1449.6～1635 nm范围内的可调谐输出.在室温25.4℃时,观测到了抽运光与信号光的和频光的光谱.实验结果表明.光参量振荡器输出光谱的半峰全宽(FWHM)小于0.5 nm.     

Calibration study of dual-band Weaver–Hartley receiver architecture

This paper presents a calibration study of dual-band image rejection receiver based on combined Weaver–Hartley architecture, with improved image rejection of first and second image signals. The system implementation is based on dual-band WLAN 802.11 a/g. When the desired signal is at 5.7-GHz band, the 2.4-GHz band becomes the first image signal and vice versa. The output IF frequency is at 30-MHz. The detection of the gain and phase mismatches is based on modeling, extraction of related error signals and correcting them in closed loop. Moreover, we demonstrate an open loop technique to reach the phase and gain correction signals. The correction signals can be digitally stored and applied as digital trimming control on the LO signals. Simulation showed close to 60 dB of image rejection ratio for the first image signal. Second image signal is rejected by a 4-section poly-phase filter.     

Amplification of WDM signals in fiber-based optical parametric amplifiers

We demonstrate for the first time, experimentally, the performance of fiber-based optical parametric amplifiers in wavelength-division-multiplexed (WDM) applications. Both a 3 /spl times/ 10 Gb/s and a commercial 7 /spl times/ 2.5 Gb/s WDM system are investigated together with the parametric amplifier. Limitations due to pump depletion and four-wave mixing are quantified. Measurements showing the performance in terms of power penalty and gain versus input-output signal power are presented.     

Noise emissions sources direction-finding in the process of their background air threats detection in radars with phased antenna array

We analyze two options of combined systems for spatial signal processing in radars with phased antenna array, where the detection of noiseless point targets with background noise emissions is accompanied by the direction finding of their sources. In the first option the direction finding of noise emissions is based on the shape analysis of the adaptive radiation pattern of the phased antenna array, formed during the adaptive target finding with background noise emissions. In the second option the bearing angles are determined on the basis of maxima of “spectral functions” of different evaluations of correlation matrix, formed on the basis of input readings. An example how to build such a combined system for spatial signal processing based on general adaptive grid filter is presented. It is shown that the effect of simultaneous target finding in external noise background and direction finding of their sources is achieved by single utilization of the most complex tuning operation of the adaptive grid filter. This operation is same for both of these tasks, and it is easier comparing to solving these two problems separately.