基于新型三环谐振器的诱导透明效应分析

针对谐振式微腔的应用需求, 提出了一种新型三环谐振式微腔结构, 类似于原子系统中的电磁诱导透明, 耦合诱导透明(CRIT)效应在一个新的光学微腔系统中已被实验证明. 该结构在硅基上由三个尺寸完全一样的微环腔组成, 通过理论分析、制备和实验测试, 能够观察到CRIT现象, 其频谱具有低群速的狭窄透明峰, 与光栅耦合器的耦合效率为34%, 并且谐振器的品质因数达到了0.65×10⁵, 同时, 失谐的谐振波长可以通过温度变化来控制, 这在旋转传感、光滤波器、光存储器等方面的应用有重要意义.     

Control of dispersion in fiber coupled resonator-induced transparency structure

Induced transparency phenomena and strong dispersion can be produced in a coupled resonator induced transparency(CRIT) structure.In this paper,we investigate the influences of structure parameters,such as amplitude reflection coefficient and loss,on transmission spectrum and dispersion of CRIT structure,and further study the control of dispersion in the structure.The results show that in the CRIT structure,adjusting the loss of resonators is an effective method of controlling dispersion and producing simultaneous normal and abnormal dispersion.When we choose approximate amplitude reflection coefficients of the two couplers,the decrease of transmittance due to loss could be effectively made up.In the experiment,we achieve the control of dispersion and simultaneous strong normal and abnormal dispersion in the CRIT structure comprised of fiber.The results indicate the CRIT structure has potential applications in optical signal processing and optical communication.     

Optical precursors in coupled-resonator-induced transparency

We experimentally examined the propagation of temporally square modulated optical pulses through a coupled ring resonator. Sharp transient spikes appeared as the square pulses entered the system. The main signal gradually grew up through coupled-resonator-induced transparency (CRIT), with the time constant determined by a second resonator. Transient spikes were attributed to the higher and lower spectral components of the incident pulse, to which the resonators cannot respond; hence, they were interpreted as optical precursors. The experiments, therefore, demonstrated that precursors and the main signal can be observed separately, with amplitudes comparable to that of the incident step in CRIT.     

A high sensitivity optical gyroscope based on slow light in coupled-resonator-induced transparency

We designed ring-in-ring planar resonator which is coupled with a straight waveguide to yield coupled-resonator-induced transparency (CRIT). The model shows an obvious effect which has a direct analogy with the phenomenon of the electromagnetically induced transparency in quantum systems. Based on this structure, a high sensitive optical gyroscope for measuring absolute rotation is proposed and analyzed. Its sensitivity scales directly with the group index whose can be reached to ¹⁰²-¹⁰⁴ orders of magnitude by using proper parameters.     

XOR/XNOR directed logic circuit based on coupled‐resonator‐induced transparency

The coupled‐resonator‐induced transparency (CRIT) effect in parallel‐coupled double microring resonators (MRRs) has been widely studied, and various applications based on the CRIT have been demonstrated. As an application of the CRIT, we propose and demonstrate a directed logic circuit that can implement the XOR and XNOR operations. Two electrical signals applied to the two MRRs represent the two operands of the logical operations, and the operational results are represented by the output optical signal. As a proof‐of‐concept, the thermo‐optic modulating scheme is employed with an operational speed of 10 kbps.     

环中环结构谐振腔中的耦合谐振透明特性研究

在考虑耦合器插入损耗的情况下,理论分析了环中环结构谐振腔的耦合谐振透明效应.利用迭代法推导了整个结构的透过系数和有效相移,从而得到考虑了插入损耗的该结构的色散.研究表明,整个结构的有效相移,群速度和带宽,可通过耦合器的插入损耗、环中环结构中环与环周长之间的倍数以及环的个数来控制,这在旋转传感、光学时延线、光缓存、滤波等方面的应用有重要意义. 关键词： 环中环结构 耦合谐振透明 色散 慢光     

Whispering gallery mode profiles in a coated microsphere

The properties of whispering gallery modes (WGM) of a microsphere can be tailored by coating the resonator with a thin film. If the coating has a higher refractive index than the microsphere core, the resulting structure will have a configuration which has similarities both with a classical WGM resonator and with a planar waveguide. By choosing the film thickness and refractive index we can tailor the degree of confinement of the WGMs inside the sphere core, coating and surrounding medium, which will in turn influence the WGMs contact with its surroundings. We present a study of the effect of the coating on the WGM mode profiles in particular of a silicon coating on a silica sphere.     

Observation of a modulation effect caused by a microsphere resonator strongly coupled to a dielectric substrate

The effect of modulation caused by a microsphere resonator is experimentally investigated with a model system consisting of a microsphere resonator and a plane substrate. We used total internal reflection microscopy (TIRM), which is a combination of conventional optical microscopy and the total internal reflection method, and observed the intensity distribution under the resonator in the evanescent-wave incidence condition. The TIRM patterns drastically change when the wavelength of the incident beam is scanned across a resonance. The response of the system is discussed on the basis of a recent proposal of traveling-wave resonance.     

Control of slow light in a ring-out-ring structure

This paper proposes a ring-out-ring structure of coupled optical resonators to yield coupled-resonator-induced transparency (CRIT). Considering the insertion loss of the coupler,it theoretically deduces the transmission and the effective phase shift. The influences of the insertion loss of the coupler on the transmittance,the effective phase shift,the group index and the CRIT linewidth are fully studied. We find that the increase in multiple m can effectively enhance the normal dispersion and the group index of the proposed structure. Moreover,the specific expression of the group index at resonance is theoretically deduced and discussed for the proposed structure with two rings. The result shows that the multiple m between the lengths of ring 1 and ring 2 can enhance the group index to m times that of the structure with two equal-sized rings at resonance. The control of slow light in the proposed structure is important for applications of highly sensitivity gyroscopes,optical delay lines and optical buffers,etc.     

混合微球谐振腔热非线性效应的增强方法

提出并实现了一种可增强微球谐振腔热非线性效应的方法。通过在微球谐振腔表面涂覆低折射率紫外胶形成并制备了混合谐振腔。通过分析混合谐振腔结构的热光系数,从理论和实验论证了混合谐振腔结构可获得更大的热非线性效应,同时验证了混合谐振腔的品质因素对热非线性的影响。应用此混合谐振腔结构于温度传感实验,结果表明通过增强方法制备的谐振腔其检测灵敏度提高了2.8倍。因此,此方法在传感应用、生物化学检测、通讯等领域也有广泛的应用前景。     

Active Q switching of a fiber laser with a microsphere resonator

We propose and demonstrate an active Q-switched fiber laser using a high-Q microsphere resonator as the Q-switching element. The laser cavity consists of an Er-doped fiber as the gain medium, a glass microsphere reflector (coupled through a fiber taper) at one end of the cavity, and a fiber Bragg grating reflector at the other end. The reflectivity of the microsphere is modulated by changing the gap between the microsphere and the fiber taper. Active Q switching is realized by oscillating the microsphere in and out of contact with the taper. Using this novel technique, we have obtained giant pulses (maximum peak power approximately 102 W, duration approximately 160 ns) at a low pump-power threshold (approximately 3 mW).     

Germanium microsphere high-Q resonator

In this Letter, the fabrication and characterization of a microsphere resonator from the semiconductor germanium is demonstrated. Whispering gallery modes are excited in a 46 μm diameter germanium microsphere resonator using evanescent coupling from a tapered silica optical fiber with a waist diameter of 2 μm. Resonances with Q factors as high as 3.8×10(4) at wavelengths near 2 μm are observed. Because of their ultrahigh optical nonlinearities and extremely broad transparency window, germanium microsphere resonators offer the potential for optical processing devices, in particular at long wavelengths, such as around 2 μm.     

Fiber laser using a microsphere resonator as a feedback element

We show that a glass microsphere resonator can be used as a wavelength-selective mirror in fiber lasers. Due to their high quality factor (Q approximately 10(8)), microsphere resonators possess a narrow reflection bandwidth. This feature enables construction of single-frequency fiber lasers even when the laser cavity is long. Nonlinear effects (such as stimulated Raman lasing) were also observed in our setup at relatively low pump powers.     

Optical microresonator based on hollow sphere with porous wall for chemical sensing

A porous-wall hollow glass microsphere (PW-HGM) was investigated as an optical resonator for chemical vapor sensing. A single mode optical fiber taper was used to interrogate the microresonator. Adsorption of chemical molecules into the nanosized pores induced a refractive index change of the thin wall and thus a shift in its resonance spectrum. The PW-HGM resonator had shown higher vapor detection sensitivity in comparison with a solid microsphere under similar test conditions.     

Optimization of prism coupling to high-Q modes in a microsphere resonator using a near-field probe

In this paper, we demonstrate a novel method for optimizing the in- and out-coupling of light confined in the fundamental high-Q whispering-gallery mode of a microsphere resonator via an external prism coupler. The technique relies on the use of a near-field probe to map the modes of the resonator and to obtain topographical information at the same time. We demonstrate the feasibility and efficiency of this technique by applying it to a sphere with a radius of 59 μm.     

Whispering gallery mode microresonators as polarization converters

A ring resonator coupled to a waveguide can be used as a highly efficient polarization converter when the input is properly polarized. We model this phenomenon and verify the predictions with a demonstration of very efficient polarization conversion (>90%) on a silica microsphere coupled to a tapered optical fiber.     

面向谐振式微光学陀螺应用的球形谐振腔DQ乘积优化

基于谐振式光学陀螺高灵敏度、低成本与微型化的发展需求, 为了实现高灵敏度的谐振式微光机电陀螺, 提出了以集成光学微谐振腔领域里高Q值、大直径谐振腔的制作为目标, 应用方向为谐振式光学陀螺的球形光学微谐振腔核心敏感单元. 在实验中以氢火焰作为热源采用熔融法制备球形光学微谐振腔. 通过调节氢气的流量控制氢火焰热源面积, 制备了不同直径(300-2200 μm)的球形谐振腔, 分析了球形谐振腔Q 值、DQ乘积、陀螺灵敏度与谐振腔直径D的对应关系及其原因, 获得了最优参数的面向谐振式光学陀螺的球形谐振腔敏感单元. D=1260 μm时, 球腔品质因数 Q=7.18×10⁷, 得到的最优陀螺灵敏度约为10°/h, 满足商业级应用的需求, 为芯片级、高精度、低成本的新型谐振式光学微腔陀螺的研究奠定了实验基础.     

Frequency tuning of the whispering-gallery modes of silica microspheres for cavity quantum electrodynamics and spectroscopy

We have tuned the whispering-gallery modes of a fused-silica microresonator over nearly 1 nm at 800 nm, i.e., over half a free spectral range, or 10(6) linewidths of the resonator. This result has been achieved by use of a new method based on the stretching of a two-stem microsphere. We describe devices that will permit new cavity QED experiments with this high- Q optical resonator when it is desirable to optimize its coupling to emitters with given transition frequencies. The demonstrated tuning capability is compatible with both UHV and low-temperature operation, which should be useful for future experiments with laser-cooled atoms or single quantum dots.     

Controlled coupling of counterpropagating whispering-gallery modes by a single Rayleigh scatterer: a classical problem in a quantum optical light

We present experiments where a single subwavelength scatterer is used to examine and control the backscattering induced coupling between counterpropagating high-Q modes of a microsphere resonator. Our measurements reveal the standing wave character of the resulting symmetric and antisymmetric eigenmodes, their unbalanced intensity distributions, and the coherent nature of their coupling. We discuss our findings and the underlying classical physics in the framework common to quantum optics and provide a particularly intuitive explanation of the central processes.     

Development of multi-wavelength microsphere fibre laser system for potential sensor applications

A multi-wavelength microsphere laser system, using a chirped fibre Bragg grating and a microsphere resonator as wavelength-selective elements and a high dopant erbium doped fibre as the gain material, has been successfully demonstrated. The multi-wavelength generation of the laser system arises from both the microsphere whispering gallery mode selection and from the additional Raman scattering inside the microsphere cavity when the erbium laser is operating at resonance with the whispering gallery modes. Through an appropriate design and fabrication of a microsphere and of a fibre taper, a selective multi-wavelength fibre laser has been realized when the pump power is above threshold required. The laser output lines created have shown much narrower linewidths than those from conventional fibre lasers and these characteristics are particularly suitable for the range of sensor applications envisaged in the work.