Investigation of gain ripple in two-pump fiber optical parametric amplifiers

By using the four-sideband theory, we analyze the gain spectrum in wideband two-pump fiber optical parametric amplifiers and predict gain ripples over the flat gain region. We derive an approximation of their pseudo-periods and discuss methods for reducing their amplitudes.     

Theoretical study of gain distortions in dual-pump fiber optical parametric amplifiers

We study analytically and numerically the small signal gain in dual-pump fiber optical parametric amplifiers by including the phase modulation of the pump waves needed for practically increasing the stimulated Brillouin scattering threshold. As for the single-pump case, we show that large signal gain distortions are generated under co-phase modulation, which depend on the rise/fall time of the phase modulation and on the fiber dispersion slope. However, it is clearly confirmed that the counter-phase modulation scheme allows to efficiently suppress these gain distortions over the whole flat gain region. In addition, we demonstrate through realistic numerical simulations that this useful technique overcomes the additional impact of pump-phase modulation to amplitude modulation conversion and zero-dispersion wavelength variations.     

Suppressing chromatic dispersion fluctuation for broadband optical parametric gain in highly nonlinear tellurite microstructured optical fibers

Optical Review - We investigate the effect of chromatic dispersion fluctuation on the performance of fiber optical parametric amplification (FOPA) using tellurite hybrid microstructured optical...     

Signal wavelength dependence of gain saturation in a fiber optical parametric amplifier

Signal gain-saturation characteristics in a fiber optical parametric amplifier are described. Experiments and calculations for the high-gain-saturation region are presented in which the direction of optical power transfer, which is from the pump to the signal and the idler in the unsaturated region, becomes reversed at high-signal-input powers. It is shown that the signal gain soon saturates for signal wavelengths far from the pump. This wavelength dependence is explained by the power-dependent phase mismatch and its behavior in the high-signal-input region.     

Hybrid flat gain C-band optical amplifier with Zr-based erbium-doped fiber and semiconductor optical amplifier

An efficient gain-flattened C-band optical amplifier is demonstrated using a hybrid configuration with a Zirconia-based Erbium-doped fibre (Zr-EDF) and a semiconductor optical amplifier (SOA). The amplifier utilizes a two-stage structure with a midway isolator to improve flat gain characteristic and reduce noise figure. At input signal power of −30 dBm, a flat gain of 28 dB is obtained from wavelength region of 1530 to 1560 nm with gain variation of less than 4 dB. The noise figure is maintained below 11 dB at the flat-gain region. This amplifier has the potential to be used in the high channel count dense wavelength division multiplexing system due to its simplicity and compact design.     

Effect of idler absorption on efficiency of optical parametric oscillators

Idler wave absorption is important in optical parametric oscillators (OPOs). We show through both numerical simulation and experiment that proper idler wave absorption coefficient could make OPOs perform better in conversion efficiency. If the coefficient becomes larger or smaller than the proper value, the conversion efficiency would be lower. A periodically poled lithium niobate (PPLN) OPO is set to verify the numerical results. Moreover, different pump power is used in the experiment research. It shows that the proper value is changing with the pump power. It shows that idler wave absorption should be considered comprehensively with pump wave power in efficiency OPO designing.     

Broadband noncollinear optical parametric amplification without angularly dispersed idler

We report a new scheme for direct generation of broadband angular-dispersion-free mid-IR idler pulses via noncollinear optical parametric amplification when group-velocity matched wavelengths cannot be found and the traditional noncollinear geometry fails to increase the phase-matching bandwidth. The scheme does not require any post-amplification idler angular dispersion compensation. We derive and interpret the condition for broadband amplification and absence of idler angular dispersion. A broadband angular-dispersion-free 2.15 μm idler pulse is generated as an experimental demonstration. We identify the potential of the scheme to generate a broadband 3.5 μm idler, with a bandwidth supporting a sub-two-cycle pulse.     

Ultra-flat and broadband two-pump optical parametric amplifiers using a single-section highly nonlinear fiber

A broadband two-pump optical parametric amplifier with ultra-flat gain spectra is proposed in a single-section highly nonlinear fiber. By elaborately setting the dispersions and pump wavelength space, a gain over 250 nm with 0.02-dB uniformity is obtained. The pump polarizations and fiber length can be changed, achieving polarization-insensitive or higher gain, while the flatness and bandwidth of gain curve remain the same.     

近红外波段宽带时间低相干光参量放大技术

在激光驱动惯性约束核聚变研究中,具有宽带、低相干特性的时间低相干光源将有望降低激光与等离子体相互作用的不稳定性,成为新一代激光驱动装置的有力竞争者。实现高功率低相干光放大输出是低相干光驱动器能否应用于惯性约束聚变领域的核心。光参量放大具有大带宽、高增益、无热效应等优势,可避免能级型放大介质的光谱窄化问题,是实现宽带低相干光放大的有效方案。系统阐述了宽带时间低相干光参量放大技术的原理和技术特性,并基于实验验证了采用非共线相位匹配的近红外波段宽带时间低相干光级联参量放大过程,最终实现7×10⁷的放大增益和13.19%的转换效率。     

非简并光学参量振荡腔的经典增益

采用双晶体串接,温度调谐及光楔补偿方法,实现了参量振荡腔内泵浦场与非简并亚谐波场之间的三模同时共振,测定了系统的经典增益,实验结果与半径典理论计算符合.     

Multistep quadratic cascading in broadband optical parametric generation

We theoretically and experimentally investigate multistep parametric processes in broadband optical parametric generators (OPGs) based on periodically poled 1 mol. % MgO-doped stoichiometric LiTaO3. We demonstrate that parametric collateral processes may deplete or enhance spectral portions of the OPG output, depending on pump pulse duration.     

宽带光参量放大过程中的转换效率提升

建立了宽带光参量放大数值模拟平台,并基于此对宽带光参量放大系统的能量转换效率提升进行优化设计,根据模拟计算结果可以对实验中能够达到的最优化能量转换效率进行预判。建立了验证实验平台并进行了实验,研究并攻克了实验中遇到的参量荧光抑制、信号光,泵浦光空间精确匹配、脉宽精确匹配、时间波形整形等关键技术难点。在抑制参量荧光的同时实现了宽带光参量放大过程能量转换效率的提升,在单级宽带光参量放大过程中获得了30%的能量转换效率。     

宽带光参量放大过程中的转换效率提升

建立了宽带光参量放大数值模拟平台,并基于此对宽带光参量放大系统的能量转换效率提升进行优化设计,根据模拟计算结果可以对实验中能够达到的最优化能量转换效率进行预判。建立了验证实验平台并进行了实验,研究并攻克了实验中遇到的参量荧光抑制、信号光,泵浦光空间精确匹配、脉宽精确匹配、时间波形整形等关键技术难点。在抑制参量荧光的同时实现了宽带光参量放大过程能量转换效率的提升,在单级宽带光参量放大过程中获得了30%的能量转换效率。     

Extended operation of synchronously pumped optical parametric oscillators to longer idler wavelengths

A synchronously pumped optical parametric oscillator, based on periodically poled lithium niobate, has operated at idler wavelengths out to 7.3 microm . Directly measured idler output powers (average) are 4.2 mW at 6.1 microm, 0.5 mW at 7.0 microm, and 0.04 mW at 7.25 microm . Characterization of the idler output indicates essentially bandwidth-limited and diffraction-limited operation.     

Continuous-wave fiber optical parametric oscillator

We report continuous-wave operation of singly resonant fiber optical parametric oscillators. In a cavity formed by 100 m of highly nonlinear fiber and two fiber Bragg gratings, the pump power threshold was 240 mW; the output wavelength could be tuned over 80 nm by tuning of the pump. We also obtained an internal conversion efficiency of 30%, compared with the maximum theoretical value of 50%, by use of a 1-km-long cavity.     

High idler conversion with an intracavity optical parametric oscillator and difference frequency generation

Tunable mid IR generation is analyzed with an optical parametric oscillator (OSO) and difference frequency generation (DFG) based on two periodically poled gratings. To obtain chirped-pulse amplification techniques, in the difference frequency generation the group-velocity must be matched. If grating periods are selected, appropriately, the wider tunable range of output pulse can be obtained. Because the group velocity is matched, the parametric bandwidth and the maximum effective length will be enhanced. We theoretically demonstrate high idler conversion in a femtosecond optical parametric oscillators with two different and cascaded periodically poled gratings. In the first grating the signal and the idler 1 are generated, while in the second one, the midwave infrared idler 2 is generated. The dependence of the lengths of the two cavities on the conversion efficiency is discussed.     

Wavelength-swept optical parametric oscillator for broadband mid-infrared spectroscopy

In this work we describe a wavelength-swept continuous-wave optical parametric oscillator (OPO) for the rapid acquisition of mid-infrared spectra spanning over hundreds of wavenumbers. Rapid tuning of a ytterbium-doped fibre pump laser resulted in the OPO idler tuning over 900 cm^?1 in 3.36 ms at a resolution of 4.5 cm^?1, within a total accessible range of 2.67 to 4.34 μm (2304–3752 cm^?1). Predictable tuning characteristics allowed simple online calibration of recorded spectra for absolute mid-infrared frequency. The system thus offers a viable approach to broadband spectral acquisition in applications requiring high-radiance illumination.     

High-energy broadband four-wave optical parametric amplification in bulk fused silica

Efficient broadband four-wave optical parametric amplification in bulk Kerr medium (fused silica) is demonstrated by means of noncollinear phase matching and cylindrical focusing geometry without the onset of beam breakup and filamentation. Amplified signal energy as high as 180 microJ with 1 ps, 1.8 mJ pumping at 1,055 nm is achieved with pump-to-signal energy conversion close to 10%. More than 70 nm FWHM parametric gain bandwidth around 740 nm is demonstrated without imposing angular dispersion on the frequency components of the broadband seed signal.     

Generation of flat optical frequency comb by fiber loop modulation

We propose a novel flat optical frequency comb generation system that employs fiber loop modulation and experimentally demonstrate its operation. Generally, when an external laser beam is injected into a fiber loop system including an optical modulator and an amplifying medium, multiple sidebands are generated exponentially. On the other hand, the fiber loop starts mode-locked oscillation at a center frequency to maximize the round-trip gain in the fiber loop from the seeds of the injected laser sidebands. By locking the sidebands from fiber loop modulation with the mode-locked oscillation in the fiber loop, the synchronous spectrum between the mode-locked oscillation and the sidebands can be shaped into a flat spectrum. Thus, a flat optical frequency comb with a flatness of about ±1 dB is obtained in the spectral bandwidth of about 1 THz.     

非单色光抽运的光参量啁啾脉冲放大的带宽及增益特性研究

采用傅里叶变换的方法将脉冲光分解成不同的频率成分,建立了非单色光抽运的光参量放大耦合方程组的数值求解模型.研究了非单色抽运光对光参量啁啾脉冲放大的小信号增益、大信号增益以及增益带宽的影响.非单色抽运光降低参量放大的增益水平,但同时可提高增益带宽,且抽运光谱宽越宽,对增益带宽的提高作用越大.还进一步从相位失配和参量带宽的角度分析了非单色抽运光使参量放大的增益降低、带宽增大的原因. 关键词： 光参量啁啾脉冲放大 非单色光 增益带宽 飞秒激光