Analysis of resonator modes in two-dimensional laser cavities containing a left-handed material

Resonator modes in two-dimensional laser cavities with curved end mirrors filled with a left-handed material were investigated numerically using the extended Fox-Li mode calculation method. The results reveal that the phase profile on the curved end mirrors of a left-handed cavity is inverted relative to that of a cavity filled with a right-handed material. Furthermore, we show that the phase on the end mirrors takes discrete values of zero and ±π under stable resonator conditions, while it varies continuously under unstable resonator conditions. The differences between stable and unstable resonators significantly alter the far-field patterns of the lowest-loss modes.     

High-order harmonic generation from plasma mirrors

We discuss the two mechanisms involved in high-order harmonic generation from plasma mirrors, and show that they can be clearly identified experimentally. The very different phase properties of the corresponding harmonics lead to light beams with different divergences. This can be exploited to select a particular type of harmonic by spatial filtering in the far-field.     

Quasi-stadium laser diodes with an unstable resonator condition

We have observed lasing in a complicated eigenmode of a quasi-stadium laser diode with an unstable resonator consisting of two curved end mirrors obeying an unstable resonator condition and two straight sidewall mirrors. The laser was fabricated by application of a reactive-ion-etching technique to a molecular beam epitaxy-grown graded-index separate-confinement heterostructure single-quantum-well GaAs/AlGaAs structure. The far-field pattern shows that the lasing mode corresponds to the complicated lowest-loss mode obtained numerically by an extended Fox-Li method.     

Intense directional lasing from a deformed square-shaped organic-inorganic hybrid glass microring cavity

Intense directional light emission from a deformed square-shaped organic light-emitting microring cavity was observed. The ring cavity was a dye-doped organic-inorganic hybrid glass film coated upon a square-shaped fiber. From the near-field and far-field emission patterns and their emission spectra we found, for the first time to our knowledge, the simultaneous existence of chaotic whispering-gallery modes and four-bounce reflection modes. The two types of mode have different emission directions, different lasing thresholds, and different spectral linewidths. High-contrast angle-modulated light emission was also observed. We could control modulation and angular spread of emission by controlling the deformation of the cavity.     

Fresnel filtering in lasing emission from scarred modes of wave-chaotic optical resonators

We study lasing emission from asymmetric resonant cavity GaN microlasers. By comparing far-field intensity patterns with images of the microlaser we find that the lasing modes are concentrated on three-bounce unstable periodic ray orbits; i.e., the modes are scarred. The high-intensity emission directions of these scarred modes are completely different from those predicted by applying Snell's law to the ray orbit. This effect is due to the process of "Fresnel filtering" which occurs when a beam of finite angular spread is incident at the critical angle for total internal reflection.     

虚共焦非稳腔腔镜倾斜对激光传输的影响

首先用几何光学方法分析了虚共焦非稳腔腔镜倾斜引起的准直光线偏离光轴,形成偏斜光线的角度灵敏度和偏斜距离灵敏度同非稳腔放大率ｍ和腔镜倾斜角β之间的关系,然后用Ｃ－６程序计算、分析了柱面条状虚共焦非稳腔单镜、双镜反向和同向倾斜三种情况下不同倾斜角对近场相位和远场强度的影响。数值结果表明,镜腔倾斜会使近场相位由均匀分布变成非均匀分布。从布导致远场光束质量变坏。     

Supercontinuum Gneneration and Modes Analysis in Secondary Cores of a Hollow-Core Photonic Crystal Fiber

We demonstrate the generation of supercontinuum spectra in three secondary cores of a hollow-core photonic crystal fiber pumped by femtosecond laser pulses, respectively. The supercontinuum spectra are mainly a result of the soliton self-frequency shift and an amplification of dispersive wave at visible wavelengths. Detailed mode simulations show that with the increasing core length, the modes transfer from ＂double-points＂ to ＂single-point＂ since the pump laser is more easily coupled into the two side cores of a secondary core when the core length is small. The simulation results also explain why the experimental observed far-field beam patterns of first two secondary cores are different.     

Stationary entanglement between macroscopic mechanical oscillators

We show that the optomechanical coupling between an optical cavity mode and two movable cavity mirrors is able to entangle two different macroscopic oscillation modes of the mirrors. This continuous variable entanglement is maintained by the light bouncing between the mirrors and is robust against thermal noise. In fact, it could be experimentally demonstrated using present technology. Received 2 September 2002 / Received in final form 10 October 2002 Published online 7 January 2003     

Coupled molecular excited states form unstable spatial modes in an optical λ/2-microresonator

We have investigated the radiation patterns formed by a quasi-planar optical λ/2-microresonator enclosing fluorescent dye molecules that were immobilized in a polymer film between two silver mirrors. Using time-resolved widefield imaging microscopy, we observed laterally confined transversal modes that occurred in the optically pumped microresonator area, exhibiting strong intensity fluctuations. The measured diameter of the isolated spatial modes was found to be 0.5 μm in agreement with theoretical predictions. The instability of the spatial mode emission patterns originates from the triplet-state-induced fluorescence intensity fluctuations of cavity-coupled collective molecular excited states.     

Quantum statistics of vacuum in a cavity with a moving mirror

We consider the electromagnetic field in a cavity when one of its mirrors can move along a given trajectory. Within a path-integral approach we calculate the Q-function of the electromagnetic field for individual modes inside the cavity and study the fluctuation properties of the field for different resonant cases.     

Optomechanical coupling between two optical cavities: Cooling of a micro-mirror and parametric normal mode splitting

We propose a technique aimed at cooling a harmonically oscillating mirror mechanically coupled to another vibrating mirror to its quantum mechanical ground state. Our method involves optomechanical coupling between two optical cavities. We show that the cooling can be controlled by the mechanical coupling strength between the two movable mirrors, the phase difference between the mechanical modes of the two oscillating mirrors and the photon number in each cavity. We also show that both mechanical and optical cooling can be achieved by transferring energy from one cavity to the other. We also analyze the occurrence of normal-mode splitting (NMS). We find that a hybridization of the two oscillating mirrors with the fluctuations of the two driving optical fields occurs and leads to a splitting of the mechanical and optical fluctuation spectra.     

Transient thermal effect of high power laser mirrors and its propagating characters of far-field

The analytical solutions of the two-dimensional transient thermal effect of high power laser mirrors are developed by using integrate transform technique. Zernike polynomials are introduced to describe aberrations of laser-induced thermal deformations. And, the corresponding expressions of the Strehl ratio and the intensity distribution are gained. Some far-field optical patterns from which we can directly see the divergence of intensity are given. The predicted results are in agreement with that of experiment.     

Hyperbolic transverse patterns in nonlinear optical resonators

We consider a nonlinear optical system in general, and a broad aperture laser, in particular, in a resonator where the diffraction coefficients are of opposite signs along two transverse directions. The system is described by the hyperbolic Maxwell-Bloch equations, where the spatial coupling is provided by the D'Alambert operator rather than by the Laplace operator. We show that this system supports hyperbolic transverse patterns residing on hyperbolas in far-field domain, and consisting of stretched vortices in near-field domain.     

一维三通道波导列阵CO_2激光器输出特性研究

由理论和实验研究了一维三通道空心桥脊波导列阵CO_2激光器的远场输出特性,观察到三种不同模态输出的远场光强分布形状.由于实验测量值与通常假定条件下理论值的偏异.本文对原假定条件进行修正.由此导出的理论表达式较好地描述了实验结果.     

Entanglement transfer from two-mode squeezed vacuum light to spatially separated mechanical oscillators via dissipative optomechanical coupling

In this paper, we propose a scheme to generate an entangled state between two spatially separated movable mirrors by injecting the two-mode squeezed optical reservoir to the dissipative optomechanics, in which the movable mirrors can modulate the linewidth of the cavity modes. When the coupling between the mirrors and the corresponding cavity modes is weak, the two driven cavity fields can respectively behave as the squeezed-vacuum reservoir for the two movable mirrors by utilizing the effect of completely destructive interference of quantum noise. Thus the mechanical modes are prepared in a two-mode squeezed vacuum state. Moreover,when the coupling between the two mirrors and the cavities modes is strong, the entanglement between the two movable mirrors decreases because photonic excitation can preclude the completely destructive interference of quantum noise, but the movable mirrors are still entangled.     

Fast and stable enhancement of the far-field peak power by use of an intracavity deformable mirror

We demonstrate that an intracavity deformable mirror (DM) is capable of compensating for the aberrations of a continuous-wave (CW) Nd:YAG solid-state laser and improving its far-field peak power fast and stably. The deformable mirror is controlled by a stochastic parallel gradient descend (SPGD) algorithm. Experimental results reveal that high-order-like transverse modes can be transformed into Gaussian-like modes quickly without any pinhole added in the laser cavity. At the same time, the far-field peak powers are also increased to different extents.     

描述激光二极管远场光强分布的理论模型

 介绍了描述激光二极管远场光强分布的几种典型理论模型,并与实验结果作了详细比较。结果表明：激光二极管的传输和远场特性应当用非傍轴理论描述,并且远场光强分布一般与输出功率大小有关。在不同功率水平下,异质结激光二极管快轴与慢轴方向的远场行为应选用不同的模型模拟。此外,还对厄米-高斯模型做了修正,考虑了奇数阶厄米-高斯模的贡献,并用厄米-高斯模的非相干叠加代替厄米-高斯模的相干叠加。改进的厄米-高斯模型能更好描述100 mW双异质结GaAlAs LD慢轴方向的远场光强分布。     

Far-field emission profiles from L3 photonic crystal cavity modes

We experimentally characterize the spatial far-field emission profiles for the two lowest confined modes of a photonic crystal cavity of the L3 type, finding a good agreement with FDTD simulations. We then link the far-field profiles to relevant features of the cavity mode near-fields, using a simple Fabry–Perot resonator model. The effect of disorder on far-field cavity profiles is clarified through comparison between experiments and simulations. These results can be useful for emission engineering from active centers embedded in the cavity.     

High-quality lowest-loss-mode lasing in GaAs quasi-stadium laser diodes having unstable resonators

We obtained high-quality lowest-loss-mode lasing in quasi-stadium laser diodes having unstable resonators that consisted of two curved end mirrors and two straight sidewall mirrors. The laser diodes were fabricated by applying a reactive ion etching technique to a metal-organic chemical-vapor deposition-grown graded-index separate-confinement heterostructure single-quantum-well GaAs/AlGaAs structure. The electrode contact area of the laser diodes was formed along unstable periodic orbits, along which the optical beams are localized. Highly directional fan-out beams corresponding to the numerically obtained lowest loss mode were emitted from the end mirrors under CW operation at room temperature.     

圆波导TE11主模辐射方向性系数的误差分析

 对不同尺寸圆波导TE₁₁模，以及TE₁₁和TM₀₁不同比例混合模式的辐射情况进行了模拟研究，得到了E面、H面功率方向图，通过高功率微波远场测量常采用的假设方向图对称的方法，计算出E面、H面方向性系数，并与模拟得到的方向性系数进行对比。结果表明：TE₁₁单模及TE₁₁模与功率占5%，10%的TM₀₁模混合情况下，H面方向性系数与模拟得到的方向性系数最大差值小于0.8 dB，E面方向性系数与模拟值最小差值大于1 dB。因此，在这些情况下，H面方向性系数更接近于方向性系数，采用H面方向性系数计算功率结果更接近实际值。