激光调制参数对光纤环型谐振腔光谱特性影响

谐振光学环型腔作为光学陀螺的核心敏感单元,其光学调制谱和与之对应的鉴频曲线的特性成为提高光学陀螺系统检测灵敏度的关键。为了研究光学陀螺的调制和鉴频谱线特性,优化陀螺性能,设计并搭建了实验测试系统,光纤环形谐振腔采用分光比为50∶50、直径17 cm的保偏光纤,总长2.2 m。使用直流高压放大器扫描窄线宽激光器（线宽小于1 kHz）的压电转化模块,扫描频率和电压分别选取20 Hz和1 V,使用模拟比例积分电路进行锁频并反馈给激光器的压电转化模块,使激光器的输出频率跟踪谐振腔实时变化。研究分析了光纤环型谐振腔在两种情况下所对应的透射谱和鉴频曲线:第一种情况为调制电压分别为2 V和4 V,对应调制频率从100 kHz到4 MHz变化;第二种情况为当调制频率为900 kHz,调制电压从2 V到10 V变化。通过实验,得到了不同调制参数下光学陀螺谱线的谐振深度、半高全宽、线性带宽、动态范围、品质因数、标度因数以及对应的锁频精度七种物理量的详细变化情况,并进一步得到了静态测试条件下三种陀螺的最佳调制频率及与之所匹配的调制电压。为进一步研究激光调制对光纤环型谐振腔光谱的影响提供指导。     

High-speed wavelength-swept semiconductor laser with a polygon-scanner-based wavelength filter

Ultrahigh-speed tuning of an extended-cavity semiconductor laser is demonstrated. The laser resonator comprises a unidirectional fiber-optic ring, a semiconductor optical amplifier as the gain medium, and a novel scanning filter based on a polygonal scanner. Variable tuning rates up to 1150 nm/ms (15.7-kHz repetition frequency) are demonstrated over a 70-nm wavelength span centered at 1.32 microm. This tuning rate is more than an order of magnitude faster than previously demonstrated and is facilitated in part by self-frequency shifting in the semiconductor optical amplifier. The instantaneous linewidth of the source is <0.1 nm for 9-mW cw output power and a low spontaneous-emission background of -80 dB.     

谐振式集成光学陀螺解调特性分析

基于激光器频率谱检测技术,沿着光的传输方向分析了光波在谐振式集成光学陀螺系统中的传播,结合输入信号特征,建立频域内的数学模型,通过数值仿真和实验得到了调频检测系统下的解调曲线。按照光的传输方向：激光器、声光晶体移频器、光波导环形谐振器、探测器,利用贝塞尔函数展开和光场耦合模理论分析了谐振式集成光学陀螺解调特性,及其调频调制检测系统解调输出信号与谐振频率偏差之间的关系。通过数值计算,分析了解调曲线的变化规律,得到了施加在激光器压电陶瓷驱动器上调制波形的最佳调制系数。在实验上搭建了激光器频率调制解调技术系统,得到了解调曲线。数值仿真和实验结果表明,当调制系数M=2时,线性工作区间斜率最大,解调曲线最好。实测形状与理论分析结果相符,从解调信号得到±2×10³ rad/s的陀螺动态范围。     

SOA-fiber ring laser and its application to electric field sensing in frequency domain

We have developed a novel optical fiber ring laser using a semiconductor optical amplifier (SOA) as the gain medium, and taking advantage of polarization anisotropy of its gain. The laser can control the oscillation frequency difference between two counterpropagating lights by incorporating a birefringent medium into the ring resonator. Since the frequency difference is proportional to the birefringence, it can be measured to detect the beat frequency generated by combining two counterpropagating lights and the laser can be applied to an optical fiber sensor whose detecting signal is in frequency domain. Electric field sensor was demonstrated with a lithium niobate crystal as a sensing probe.     

光纤复合环形腔单模激光器的研究

单模光纤激光器在光通讯和光传感中具有广阔的应用前景。分析了复合腔光纤激光器的构成及单模的实现特点,提出了一种新颖的光纤复合环形腔激光器结构,并对其进行了实验研究。该激光器使用了波长为980nm的半导体激光器作为泵浦源。三个腔长均为2m,彼此之间的腔长差为1～2mm的光纤环形滤波器与主谐振腔构成复合腔。此激光器在波长为1562nm处得到了线宽小于0.1nm的单模激光输出,输出的光功率可达到1mW。该激光器的阈值为5mW,斜率效率为4%。     

Quasi-monolithic ring resonator for efficient frequency doubling of an external cavity diode laser

A quasi-monolithic second-harmonic-generation ring resonator assembled with miniaturized components is presented. The ring contains a 10-mm-long bulk periodically poled lithium niobate crystal for second-harmonic generation, four plane mirrors and two gradient-index lenses. All parts are mounted on a glass substrate with an overall size of 19.5 mm×8.5 mm×4 mm. As pump source a broad-area laser diode operated in an external resonator with Littrow arrangement is utilized. This external cavity diode laser provides near diffraction limited, narrow-bandwidth emission with an optical output power of 450 mW at a wavelength of 976 nm. Locking of the diode laser emission to the resonance frequency of the ring cavity was achieved by an optical self-injection locking technique. With this setup more than 126 mW of diffraction-limited blue light at 488 nm could be generated. The opto–optical conversion efficiency was 28% and a wall plug efficiency better than 5.5% could be achieved.     

Measurements of excess loss of the crossed waveguide using optical waveguide ring resonators

Crossed waveguide is widely used in optical devices, whose excess loss has a strong impact on multi-turn optical waveguide ring resonator and resonator integrated optic gyro. The resonance curve of the ring resonator is sharply dependent on the loss within the resonator. This paper presents how to get excess loss of the crossed waveguides nondestructively through the comparison of the resonance characteristics between one-turn and multi-turn optical waveguide ring resonators.     

机械抖动棱镜式激光陀螺出射光强度特性

针对棱镜式激光陀螺在抖动状态下出射光强度被调制的现象, 系统地研究了机械抖动对棱镜式激光陀螺中光传输轨迹和光电探测器的影响机理. 在对现有棱镜式激光陀螺性能进行分析的基础上, 应用数值模拟和有限元分析方法, 将对称型全反射棱镜纳入四棱镜陀螺的结构设计方案, 并给出了由机械抖动引起的应力双折射和光电探测器位置偏移与出射光强度的一般关系. 结果表明, 机械抖动会使棱镜产生应力双折射, 使激光光路发生改变, 同时造成光电探测器与出射光束产生相对位移, 导致出射光强度幅值产生调制. 使用全对称型的陀螺结构, 选取具有合适折射率的对称型棱镜, 减小探测器与出射光斑中心的相对位移, 可以将出射光强度调制幅值相比原先减小52.63%以上, 显著地改善出射光强度被调制的现象. 此分析结果为提高激光陀螺的可靠性提供了重要参考.     

激光陀螺中的光学抖动及其对锁区的影响分析

为了提高激光陀螺的性能,提出利用光学抖动改善陀螺锁区的方法.研究了环形光路中背向散射对锁区的影响,理想状态下可以消除陀螺的零阶锁区.在微扰条件下对光学抖动下陀螺腔内的光路变化进行了分析计算,得到了使陀螺锁区达到最佳改善的理论光学抖动量并进行了实验研究.实验结果表明:光学抖动可以起到类似机械抖动加噪的效果,改善陀螺的零偏稳定性.     

在ITU波长上的多波长光纤激光器

实验演示了一种基于半导体光放大器的多波长光纤激光器,其输出波长在ITU的波长上。使用环形腔结构,应用光纤Fabry-Perot标准具来获得ITU波长间隔,同时获得了上百条激光谱线的输出,在60nm范围的功率波动小于5dBm。     

Silica waveguide ring resonators with multi-turn structure

Optical waveguide ring resonator is the basic element of resonator integrated optic gyro (RIOG). In this paper, we report a novel configuration of optical waveguide ring resonator using a multi-turn structure. The characteristic of the light propagating across the crossed waveguides is analyzed using the finite difference beam propagation method. The relationship between the propagation loss and the intersection angle for arbitrary intersecting angles has been analyzed. Some crossed waveguides are fabricated in silica waveguides to verify the theoretical results. On this basis, the influences of the loop numbers and the excess loss of the crossed waveguide on the limited sensitivity of the RIOG have been analyzed. There is a critical intersection angle for certain resonator, only when the intersection angle is bigger than the critical angle, the gyro sensitivity can be improved by increasing the loop numbers. This will be helpful to how to determine the optimum length in resonator for its application in RIOG.     

Wavelength-tunable optical pulse generation from a fiber ring laser with a reflective semiconductor optical amplifier

This work describes, for the first time, wavelength-tunable optical pulse generation from a fiber ring laser with a reflective semiconductor optical amplifier. The optical signal to noise ratio of this fiber laser is higher than 49 dB over the wavelength-tunable range of 16 nm. Performance of this fiber ring laser operated at different wavelengths is also discussed.     

Optical bistability in a single-bus InGaAs micro-ring resonator array

In this paper, we investigate the optical bistability induced by optical nonlinearity in a compact parallel array of micro-ring resonators with radius of 5 μm. Due to the nature of perfect light confinement in this structure, resonance and accumulation process in a ring resonator and optical nonlinear effects, are observable even at small optical power (a few milliwatts). Different optical applications such as all-optical switching, optical memory devices, logic gates and modulators are possible, due to optical bistability in a ring resonator. Using alternative semiconductor compounds, instead of silicon that have weak nonlinear optical properties, we improve the performance of ring-resonator based devices. Here we use a polymer cladding layer with negative thermo-optic coefficient. Using this structure we can eliminate the temperature created nonlinearity which is a very slow process. Therefore, the switching speed increases from a few MHz to several tens of GHz. By plotting the transfer function of the resonator, a hysteresis loop is observed in a few milliwatts. Although, using a ring resonator array the bandwidth reduces, however, the width of the hysteresis loop and resolution between both steady state increases.     

Proposal of a semiconductor ring laser gyroscope

We proposed a novel optical inertial rotation sensor using a semiconductor ring laser (SRL). The frequency difference between the two counter propagating oscillation frequencies was automatically generated in a mechanically rotated SRL, which consisted of a pig-tailed laser diode amplifier module. And the Sagnac frequency shift could be detected at the first time as a beat note by the terminal voltage change of the SRL without branching the circulating optical power. These experimental results verify that an SRL operates as an optical inertial rotation sensor based on the Sagnac effect.     

SOA-based fiber ring laser use in a photonic radio-frequency phase shifter

This investigation demonstrates the feasibility of a semiconductor optical amplifier (SOA)—based fiber ring laser use in a photonic radio-frequency (RF) phase shifter. Experimental results indicate that a fiber ring laser can successfully replace an external pump laser in a photonic RF phase shifter. The RF phase shifter can be turned by adjusting the power of the fiber ring laser.     

光纤环形谐振腔的频率锁定及其特性

基于可调分束比的光纤分束器,制作了光纤环形谐振腔并通过调节分束比实现了对光纤环形谐振腔的欠耦合、临界耦合和过耦合的状态控制.实验测量了腔最小反射率与腔损耗之间的关系,获得光纤环形谐振腔的腔内衰减率为κ_0=2π×(1.60±0.03) MHz ,品质因子为Q=(1.10±0.02)×10.8.在此基础上,结合了压电陶瓷拉伸光纤以控制腔长和Pound-Drever-Hall锁频两大技术优势,克服了之前温度反馈控制等方法的反馈带宽窄、噪声大和稳定性差等问题,实现了对光纤环形谐振腔共振频率的快速、灵敏的控制和锁定.结果表明,锁频过程中相位调制功率与相位调制引起腔反射光的强度调制之间的关系为线性关系,进而通过降低相位调制信号的功率以减小相位调制对腔反射光强度调制的影响.当调制功率设定最低为–9 dBm时,光纤环形谐振腔仍能被稳定锁定.该光纤环形谐振腔为其与原子、金刚石色心等发光粒子相互作用的腔量子电动力学实验研究奠定了坚实的基础.     

Stopping and storing light pulses within a fiber optic ring resonator

A simple all optical system for stopping and storing light pulses is demonstrated. The system consists of an erbium-doped fiber amplifier （EDFA）, a semiconductor optical amplifier （SOA）, and a fiber ring resonator. The results show that the multisoliton generation with a free spectrum range of 2.4 nm and a pulse spectral width of 0.96 nm is achieved. The memory time of 15 min and the maximum soliton output power of 5.94 dBm are noted, respectively. This means that light pulses can be trapped, i.e., stopped optically within the fiber ring resonator.     

Tunable 12×10 GHz mode-locked semiconductor fiber laser incorporating a Mach-Zehnder interferometer filter

A stable multiwavelength mode-locked semiconductor fiber ring laser incorporating a fiber Mach-Zehnder interferometer (MZI) filter was proposed and experimentally demonstrated. A semiconductor optical amplifier (SOA) serves as an optically controlled mode-locking element due to gain exhaustion caused by external injected optical pulses. Another SOA severs as a constant-gain medium. A fiber MZI filter with a temperature control is incorporated into the fiber ring cavity to acquire a stable and tunable multiwavelength oscillation. Twelve wavelengths are synchronously mode-locked at 10 GHz, pulse width of mode-locked pulse are about 30 ps. Proposed multiwavelength mode-locked semiconductor fiber ring laser has some distinct advantages, such as simple and compact structure, easy integration, convenient tuning, good stability, potential high repetition rate operating, which has potential application in the future WDM communication system.     

Entangled photon states generation and regeneration using a nonlinear fiber ring resonator

We propose a simple system of the entangled photon states generation and regeneration using a standard diode laser, a Mach Zehnder Interferometer (MZI) and a fiber optic ring resonator (FORR). Light from the diode laser is launched into an MZI and circulated in the FOOR, without any optical pumping components included in the system. The nonlinear light pulses are generated by a Kerr nonlinear effects type, while the resonance peaks are formed by the four-wave mixing of light pulses in the FORR. The entangled photons can be performed by using the polarization control device, and then detected by the avalanche photo-detectors, where the entangled photon visibility is plotted and seen. Similarly, the entangled photon states can be easily formed by using the appropriated coupling ratios into a fiber coupler, then into a ring resonator, i.e. without an MZI. The use of the entangled photons generation based on a fiber optic scheme for quantum teleportation, quantum key distribution via optical wireless link, and the system of the entangled photon states recovery by using a fiber ring resonator incorporating an erbium-doped fiber (EDF) have been investigated and discussed. The feasibility of dense coding using multi-entangled photons generation based on the fiber optic scheme and the effect of the entangled state walk-off along the optical fiber are also discussed, respectively.     

850 nm centered wavelength-swept laser based on a wavelength selection galvo filter

A wavelength-swept laser is constructed using a free space external cavity configuration coupled with a fiberbased ring cavity at the 850 nm region. The external cavity filter employs a galvo-mirror scanner with a diffraction grating for wavelength selection. The filter is connected to a ring cavity through an optical circulator.The ring cavity contains a broadband semiconductor optical amplifier with a high optical output. The performance of this laser is demonstrated with broad bandwidths and narrow linewidths. The 3 dB linewidth and the bandwidth of this source are 0.05 nm(~20 GHz) and 48 nm, respectively. The maximum output power is 26 m W at 160 m A current.