Narrowband optical filter, with a variable transmission spectrum, using stimulated Brillouin scattering in optical fiber

A novel shape-adjustable narrowband optical filter utilizing stimulated Brillouin scattering in an optical fiber is proposed and demonstrated. In this scheme, binary-phase-shift-keying modulation is applied to the pump wave to broaden and shape the Brillouin gain spectrum. By choosing an appropriate modulation data pattern, we realized a flat-top steep-cutoff optical bandpass filter with a 3-dB bandwidth of 1.5 GHz and a 10-dB bandwidth of 2 GHz is realized. In addition, a tunable optical notch filter is also realized by deamplification of the anti-Stokes wave.     

50 dB parametric on-chip gain in silicon photonic wires

A pulsed mid-infrared pump at λ=2173 nm is used to demonstrate wideband optical parametric gain in a low-loss 2 cm long silicon photonic wire. Using dispersion engineering to obtain negative second-order (β2) and positive fourth-order (β4) dispersion, we generate broadband modulation instability and parametric fluorescence extending from 1911 nm-2486 nm. Using a cw probe signal to interrogate the modulation instability spectrum, we demonstrate parametric amplification >40 dB with an on-chip gain bandwidth wider than 580 nm, as well as narrowband Raman-assisted peak gain >50 dB.     

All-optical microwave notch filter with flat passband based on semiconductor optical amplifier

An all-optical filter structure for interference mitigation of microwave signals is proposed and demonstrated. The structure is based on a recirculating delay line loop (RDLL) and a fiber Bragg grating. The RDLL is comprised of a semiconductor optical amplifier (SOA) followed by a tunable narrowband optical filter and an optical variable delay line. Negative tap is generated using wavelength conversion based on the cross-gain modulation of amplified spontaneous emission spectrum of the SOA. A negative band-pass filter and a broadband all-pass filter are synthesized to achieve a narrow notch filter with flat passband which can excise interference with minimal impact on the wanted signal over a wide microwave range. Experimental results show the notch rejection ratio of 30 dB, good shape factor and tunability.     

新型小尺寸窄带偏振分光器在光纤通信中的应用

在光纤通信中,为了在不改变调制波长范围的基础上仍能实现更多数据通道的波分复用,设计了一种新型的小尺寸窄带偏振分光器,用于对现有的数据通信网络进行扩容以及提高光信号的信噪比。在该分光器上蒸镀了两种新设计的膜系,一层是窄带滤光膜,另一层是偏振分光膜。采用TFCalc软件仿真,设计结果中窄带滤光膜的带宽约为0.4 nm,偏振分光膜在1 530～1 560 nm范围内对p光的通透性能优于99.8%。基于以上膜系设计在BK7光学玻璃上实际制备两组膜系,实验采用Agilent 8164-A型光波测量系统对经过膜后的光进行光谱分析。结果显示,窄带滤光膜的实际带宽优于0.4 nm,增益平坦度小于-0.05 dB,相比现有常见的0.8 nm滤光膜具有更窄的带宽,可以实现在调制波长范围不变的条件下增大波分复用的数据通道总量。偏振滤光膜的实际p光透光率为99.6%,相比仿真值略低,但仍优于设计要求,相比传统分光器的光信号强度保留效果更好,具有更高的信噪比。综上所述,该分光器具有更好的应用价值和实用意义。     

Narrowband switchable dual-passband atomic filter with four-wave mixing optical amplification

By using Faraday optical filter combined with four-wave mixing (FWM) amplifier, a narrow bandwidth optical amplifying atomic filter with switchable dual-passband is demonstrated experimentally. The two transmission peaks of the filter correspond to the Stokes and anti-Stokes frequencies, exhibiting a Raman gain in 13- and 17-fold, respectively, with bandwidth of ～120 MHz. By properly setting pump laser detuning, switching between filter passbands is realized. We also investigate the dependence of peak transmission on both pump laser intensity and Rb cell temperature. This atomic filter can find practical applications in long-distance laser communications and laser remote-sensing systems.     

All-optical modulation at 1.3 μm wavelength in the inGaAsP/InP system

All-optical, normal-to-surface modulation in InGaAsP epitaxial layers, lattice matched to InP, is investigated. Close to the gap wavelength of 1.3 m a transmission increase under optical excitation is observed. A modulation depth of 34% is achieved for 0.8 mW pump power at 790 nm wavelength. The modulation frequency is limited by excess carrier lifetime. A 3 dB frequency of 80 MHz is achieved with a 10 dB decrease at 400 MHz. A lateral electric field enlarges the bandwidth but decreases the modulation depth. For weak excitation the experiments are well described in terms of direct electronic transitions between parabolic bands or in terms of simple band filling. The devices are well suited for parallel optical data processing.     

基于一维耦合腔光子晶体的声光可调谐平顶滤波器的研究

本文利用一维耦合腔光子晶体,提出了一种声光可调谐平顶滤波器.该滤波器利用声光效应,通过改变超声波频率使一维耦合腔光子晶体透射谱的平顶滤波器的中心波长产生漂移,从而实现可调谐的滤波功能.基于传输矩阵法和声光效应理论,建立了这种平顶滤波器的理论模型;利用COMSOL软件,对平顶滤波器的矩形度、通带带宽、插入损耗、可调谐特性、加工精度进行仿真研究.研究结果表明,通过施加频率为6-11 MHz的超声波,可实现通带带宽为5-6 nm及中心波长在1514-1562 nm范围内可调谐的平顶滤波器;在可调谐范围内通带带宽内插入损耗不超过2.23 dB,最低仅为0.78 dB,矩形度最低可达1.4;加工误差在±10 nm内平顶滤波器的中心波长、矩形度、插入损耗、通带带宽出现的偏差很小.该平顶滤波器具有易于设计和集成、通带平坦、可调谐范围宽、通带带宽稳定、插入损耗低、品质因素高的特点,在光开关、可调谐光纤激光器、光纤传感等光通信领域有重要应用.     

High-gain and low-distortion Brillouin amplification based on pump multi-frequency intensity modulation

Using a pump with a multi-line spectrum to broaden the Brillouin gain bandwidth is an effective way to achieve lowdistortion amplification with high gain. Here, we theoretically and experimentally investigate the generation of a broadband Brillouin gain spectrum based on multi-frequency intensity modulation in an optical fiber. The arbitrary bandwidth of the Brillouin gain spectrum of stimulated Brillouin scattering(SBS) can be obtained as expected. In our experiment, a broadband Brillouin gain spectrum with a bandwidth of about 200 MHz is demonstrated. We also achieve a low-distortion amplification of a weak signal, whose maximum magnification is 65 d B for a-68-dBm input power signal.     

双锥光纤中声光效应的理论分析

利用耦合模理论分析了在双锥光纤耦合区中声光的相互作用,讨论了在不同耦合区半径下扰动周期与声波频率的关系。计算了在双锥光纤中声光谐振耦合的波谱特性和模式转换效率、带宽与调制周期和耦合区长度的关系。介绍了声光的可调谐性。基于此效应可制作全光纤可变衰减器和可调滤波器。     

Actively mode-locked fiber ring laser by intermodal acousto-optic modulation

We report an actively mode-locked fiber ring laser. A simple and low-insertion-loss acousto-optic modulator driven by standing flexural waves, which couples core-to-cladding modes in a standard single-mode optical fiber, is used as an active mechanism for mode locking. Among the remarkable features of the modulator, we mention its high modulation depth (72%), broad bandwidth (187 GHz), easy tunability in the optical wavelength, and low insertion losses (0.7 dB). The narrowest optical pulses obtained were of 95 ps time width, 21 mW peak power, repetition rate of 4.758 MHz, and 110 mW of pump power.     

S波段窄带带通体声波滤波器设计

针对无人机测控应用设计了一种S波段窄带带通体声波(BAW)滤波器,其技术指标为:中心频率2.46 GHz,带宽41 MHz,带内插损大于-3 dB,带内纹波小于1 dB,带外抑制小于-40 dB@2.385 GHz和2.506 GHz。采用Mason模型设计了BAW滤波器中各薄膜体声波谐振器(FBAR)的叠层结构;使用变迹法设计了各FBAR(电极)的形状;采用一种自行开发的自动布局方法得到紧凑的BAW滤波器布局;建立了BAW滤波器的声-电磁协同仿真模型,通过这种高保真的多物理场仿真方法对设计结果进行了性能验证。该设计流程是通用的,并且有两个特点:采用声-电磁协同仿真方法对设计阶段的BAW滤波器进行最终性能检验,可以及早发现并拒绝1D Mason模型过于乐观的设计;滤波器布局设计中采用了一种新的自动化布局方法,大大简化了在此阶段的反复尝试工作,也为声-电磁协同仿真模型输出了必需的面内结构信息。     

Detailed theoretical investigation on relative intensity noise reduction enhancement based on reflective SOAs

The enhanced performance for relative intensity noise (RIN) reduction based on reflective semiconductor optical amplifiers (R-SOA) has been investigated theoretically by comparison with conventional transmission SOA. The results show that, by selecting appropriate input optical power, as large as >20 dB RIN suppression improvement can be achieved for R-SOA, without sacrificing the noise rejection bandwidth. With increased injection current, the optimized input signal power is decreased and the operation region is extended for the best RIN reduction. For RIN suppression in WDM spectrum slicing, the bandwidth optimization of receiver filter should be performed to avoid the spectral broadening induced by self-phase modulation (SPM) and four wave mixing (FWM). Our derived result is helpful for designing and optimizing the R-SOA in application of noise suppression enhancement.     

利用离子交换技术制备跑道形波导谐振腔滤波器的研究

采用AgNO3和KNO3混和熔盐作为离子交换源,在K9玻璃上制备了跑道形波导谐振腔滤波器。利用ASE宽带光源和光谱仪对器件特性进行了测试,得到的该滤波器自由光谱范围为0.176nm。对比对Cr=4dB和3dB带宽δλ=0.13nm来说,耦合系数和传输损耗分别为к=0.9和α=3.2dB/cm。测试了环形腔的热光调相特性,在16℃的变化范围内实现了2π的相移。通过分析,波导材料的热光系数约为1.49×10-5/℃。该滤波器不仅可用于滤波、传感等领域,而且也可与其它波导结构相结合实现新的功能。     

光纤移频分布式布里渊光纤传感技术

提出了一种利用布里渊光纤环形腔移频技术实现分布式光纤布里渊传感的方法.该方法基于布里渊光时域分析法原理,将一束单纵模运转激光器输出的激光分为两束|一束光入射布里渊光纤环形腔中产生窄线宽的受激布里渊散射光作为斯托克斯光,另一束光经过低频相位调制后作为泵浦光|斯托克斯光和泵浦光分别相向入射进入传感光纤,通过测量布里渊谱得到光纤温度或应变.利用该方法可将十几GHz的微波频率转化为兆赫信号频率进行探测处理,仅需一台激光器,因此系统结构简单、成本低,还可减小激光器频率波动对测量准确度的影响.实验验证了该方法的可行性.     

High efficiency, high repetition rate, all-fiber picoseconds pulse MOPA source with 125?W output in 15?μm fiber core

A passive mode-locked fiber laser-delivered 13?ps pulse is saturatedly amplified with a four-stage amplifier chain. 125?W high power all-fiber picoseconds pulse laser is demonstrated in a 15-??m fiber core, and the optical-to-optical conversion efficiency of the main amplifier is up to 86.12?%. A home-made (6?+?1)?×?1 fiber combiner is used to couple the pump light and signal light into the gain double cladding fiber. In order to suppress the nonlinear effects in high-power picosecond fiber amplifiers, the repetition rate of the seed pulse is increased from 60?MHz to?~1?GHz; also the gain fibers are advisably selected. The amplified output spectrum is symmetrically broadened to several nanometers due to self-phase modulation (SPM). No stimulated Raman scattering (SRS), amplified spontaneous emission (ASE) and residual pump light are observed and the optical signal-to-noise ratio is more than 30?dB. The all-fiber picoseconds MOPA laser in this report can be easily performed with the conventional fiber handing equipments, and it has great potential to be applied as pump source in the fields of optical parametric oscillator, laser frequency-doubling and supercontinuum generation.     

Ultranarrow bandwidth tunable atomic filter via quantum interference-induced polarization rotation in Rb vapor

We report the experimental demonstration of an ultranarrow bandwidth atomic filter by optically induced polarization rotation in multilevel electromagnetically induced transparency systems in hot Rb vapor. With a coupling intensity of 2.3 W/cm^2, the filter shows a peak transmission of 33.2% and a bandwidth of 10 MHz. By altering the coupling frequency, a broad tuning range of several Doppler linewidths of the D1 line transitions of STRb atoms can be obtained. The presented atomic filter has useful features of ultranarrow bandwidth, and the operating frequency can be tuned resonance with the atomic transition. Such narrowband tunable atomic filter can be used as an efficient noise rejection tool in classical and quantum optical applications.     

基于古斯-汉欣位移的双通道窄带滤波器

本文利用光束在对称金属包覆波导表面反射得到的异常大的古斯-汉欣(Goos-Hänchen)位移,通过实验实现了双通道窄带滤波.当入射激光波长为859.60 nm时,两通道滤波的峰值位置分别为859.604 nm和859.688 nm,峰值半宽(FWHM)为0.036 nm,而消光比达到15.3 dB.峰值波长可通过改变入射角或小孔位置实现调谐. 关键词： 古斯-汉欣(Goos-Hä nchen)位移 光波导 双通道 滤波器     

All-optical microwave bandpass filter and phase shifter using a broadband optical source and an optical phase modulator

We propose a system that can perform microwave bandpass filtering and phase shifting simultaneously without redundant optical-electrical and electrical-optical conversions. The principle is based on polarization-dependant phase modulation of a broadband optical source and the variable optical carrier time shift method. A single-bandpass microwave photonic filter with a central frequency of 10.8 GHz, a 3-dB bandwidth of 670 MHz, and a 360° phase tuning range is experimentally demonstrated. The capability of our configuration to implement wideband phase shifters is also verified.     

Ultra-narrow bandwidth atomic filter based on optical-pumping-induced dichroism realized by selectively saturated absorption

We report an ultra-narrow bandwidth atomic filter based on optical pumping induced dichroism. Induced-dichroism-excited atomic line filters in previous research used a pump to populate atoms on special Zeeman sub-levels, so only one sigma component of the probe undergoes absorption while the other one can pass through the medium freely because of dipole forbidden. Unlike in previous research, we proposed a novel method to get circular dichroism realized by “selectively” saturated absorption in rubidium. In the experiment, we observed three transmission peaks: the principle of the first two is the same as the previous research, while the third one is realized by selectively saturated absorption, which has a peak transmission of 14.9% with 61 MHz bandwidth.     

CDMA基站用14阶高温超导滤波器

研制了用于CDMA移动通信基站接收机前端的14阶高温超导带通滤波器。该滤波器的设计带宽为10.9 MHz,中心频率为830MHz;仿真得到的回波损耗约为28 dB,带内波动小于0.008 dB,带外抑制大于90 dB;该滤波器由MgO衬底上的双面DyBa2Cu3O7超导薄膜加工而成。该滤波器在无后期调谐的情况下,72K温度的实测带宽为10.9MHz,回波损耗好于20dB,插入损耗0.001 dB,边带陡峭度高达80dB/16.3MHz,实测的中心频率等指标也与仿真设计结果吻合很好,各项指标均满足应用要求。