Statistical Properties of a Ring Laser with Injected Signal and Backscattering

The Statistical Properties of a homogeneously broadened ring laser with an injected signal are investigated and the normalized two-mode intensity auto-and cross-correlation functions are calculated by a full saturation laser theory with backscattering.The theoretical predictions are in good agreement with the experimental measurements.Further inverstigation reveals that the backscattering can reduce the fluctuations in the system while the full saturation effect plays a major role when the laser is operated above threshold.It is also quite important to notice that the injected signal can drive the weak mode from incoherent light to coherent light.     

Amplitude-squeezed emission from a transverse single-mode vertical-cavity surface-emitting laser with weakly anticorrelated polarization modes

We discuss the polarization-resolved intensity noise characteristics of a transverse single-mode vertical-cavity surface-emitting laser (VCSEL). Measurements by a sensitivity-enhanced lock-in amplifier detection scheme yield only an imperfect anticorrelation between the strong and the weak orthogonally polarized fundamental modes. Yet the total emission shows amplitude squeezing of 0.4 dB below the shot-noise level. Unlike for transverse two-mode emission, a perfect anticorrelation between the two polarization modes is not necessary for generation of amplitude-squeezed emission in a transverse single-mode VCSEL, in agreement with theoretical predictions.     

The role of population pulsations in single-mode laser instabilities

This paper gives three principal results: One, population pulsations are responsible for both the multiwavelength and the chaotic single-wavelength instabilities of single-mode operation in unidirectional ring lasers containing homogeneously-broadened media. Two, in appropriate limits the Fourier expansion method for treating three-frequency operation in saturation spectroscopy is equivalent to the linear stability analyses in laser theory and optical bistability. Three, inclusion of population pulsations significantly increases the instability range over that predicted by Casperson for single-mode bad-cavity lasers containing inhomogeneously-broadened media.     

Colored noise in a two-dimensional nonlinear system

A two-dimensional decoupling theory is developed when colored noise is included in a nonlinear dynamical system. By a functional analysis, the colored noise is transformed to an effective noise that includes the noise correlation time, the mean dynamical variable, and the original noise strength. When the two-dimensional decoupling theory is applied to single-mode and two-mode dye laser systems, the mean, variance, and effective eigenvalue of laser intensity are calculated. Excellent agreement between theoretical analysis, numerical simulations, and experimental measurements are obtained. It is seen that the increase of noise correlation time can reduce the fluctuations in the laser system. It is also shown that there is relatively large fluctuation in the phase when the laser undergoes from thermal light to coherent light when the theory is applied to a single mode dye laser. Received 20 August 2001 and Received in final form 4 December 2001     

一种双模压缩微波制备的相位锁定方案

相位锁定是双模压缩微波制备的关键问题之一.针对基于超导180°混合环的制备方案相位稳定度不高且信息处理复杂等问题,提出一种相位锁定方案.对约瑟夫森参量放大器的信号输入进行相位调制,输出的单模压缩微波与另一未调制的同频单模压缩微波在超导180°混合环内干涉,实现双模压缩微波的制备与路径分离.将未调制的单模压缩微波与一路双模压缩微波混频,解调出相位调制信号可得到两路单模压缩微波的相对相位及误差,将相位误差反馈于约瑟夫森参量放大器的抽运实现相对相位的锁定,获得稳定的双模压缩输出.本研究对高性能纠缠微波源的设计提供了理论参考.     

单模光纤激光极限功率的数值研究

对光纤激光极限功率的探索和其受限因素的分析, 有利于为大功率光纤激光器的发展提供理论依据和实验指导. 本文考虑热效应、光效应、非线性效应和抽运亮度等因素对光纤激光极限功率的影响, 分析了掺镱和掺铥光纤的极限功率和受限因素. 在此基础上, 结合激光在光纤中单模传输的条件, 计算了单模掺镱和掺铥光纤激光的极限功率. 计算结果表明, 在现有技术条件下, 使用常规的976 nm和793 nm激光二极管抽运, 单模掺镱和掺铥光纤激光的极限功率分别为4.2 kW和7.8 kW, 其中单模掺铥光纤激光的功率水平还远低于它的极限功率的原因是受抽运亮度的限制. 最后分析指出减小纤芯的数值孔径和改进少模光束的光束质量是提升单模光纤激光极限功率的重要途径.     

随机激光器的理论与研究现状

综述了随机激光器的最新理论与实验进展，对光散射理论、环形腔理论、环形波导理论等各种随机激光理论的内容、应用范围及其差异等进行了重点分析和评述，并介绍了一些随机激光器的重要实验。讨论了随机激光器未来的发展，并描述了随机激光器潜在的应用前景。     

Theoretical and experimental study on rare-eath element-doped silicon single-mode fiber laser with two different structures of resonators

Abstract: Laser resonator is very important in the study and fabrication of lasers. The work conditions and work parameters of rare-earth element-doped optical fiber lasers with two different structures of laser resonators, i. e., the fiber ring resonator and Fabry-Perot resonator are studied. The fineness, laser resonant conditions, laser oscillation conditions and threshold inversion of these two different cavity are deduced. A series of experiments are also given. The result is very valuable to evaluate the output of optical fiber laser and can be a foundation of device fabrication. The Nd~(3 )-doped silica single-mode fiber laser pumped by Ar~ laser with a low threshold of 1.02 mW and a maximum output of more than 1 mW are presented in this paper.     

Theory and experiment of CW dye laser injection locking and its application to second harmonic generation

High-power single-mode operation of a cw ring dye laser has been obtained by injection of cw single-mode radiation. The intracavity power of this system was used to generate tunable single-mode uv radiation by frequency doubling in a temperature phase-matched ADA crystal: up to 45 W intracavity fundamental power and up to 70 mW extracted uv power have been observed. A theoretical treatment of the injection locked cw ring dye laser system is given for the stationary state. Expressions for the intracavity intensities as a function of the small-signal gain and the saturation intensity are derived.     

Coherent combining of fiber lasers using a ring coupled cavity and?single-mode fiber filtering

Coherent combining of two fiber lasers has been experimentally demonstrated by using a ring coupled cavity and single-mode fiber filtering technique. Their phases are primarily synchronized due to mutual injection coupling introduced by a common ring coupled cavity, and efficient phase locking is realized by utilizing a single-mode feedback fiber to filter the far-field pattern. The detailed experimental investigations indicate that the stability of phase locking can be improved significantly by this spatial filtering technique, and the far-field intensity distribution can be manipulated by controlling the position of the filtering fiber.     

Ξ型三能级原子玻色-爱因斯坦凝聚体单模光场系统中双模原子激光的压缩性质

研究了Ξ型三能级原子玻色-爱因斯坦凝聚体单模光场系统中双模原子激光的压缩性质.结果表明:双模原子激光能被周期性压缩,并且具有量子Rabi振荡和崩塌-回复现象两种形式的振荡.最大压缩深度和崩塌-回复振荡频率主要依赖于光场与原子间相互作用强度,量子Rabi振荡频率主要由光场圆频率决定.     

Dynamical Properties of Bidirectional Ring Laser with Both the Additive and Multiplicative Noises and Saturation Effect

The dynamical properties of a two-mode ring laser with both the additive and multiplicative noises are analyzed. Time-dependent probability density is obtained by the method of one-dimensional approximation. Some special behaviors of T_c and λ_eff are discussed when the multiplicative pump noise and saturation effect are included in the laser theory.     

Noise and amplitude-squeezing performance of two-polarization-mode semiconductor lasers

Using a theoretical semiclassical approach, we study in detail the amplitude fluctuations and correlations of a two-orthogonal polarization-mode semiconductor laser as obtained from a vertical-cavity surface-emitting laser (VCSEL). We demonstrate that there exists the possibility of squeezing in the two-mode regime besides sub-shot-noise emission in the well-known ideal single-mode operation regime. These theoretical results confirm a recent experimental demonstration of the generation of amplitude-squeezed light with VCSEL's.     

Effect of backscattering on the behavior of a dye ring laser

The effect of backscattering on the behavior of a dye ring laser is investigated by photoelectric counting measurements. It is found that there exist two laser regimes, a low backscattering regime in which the laser exhibits meta-bistability and random mode switching, and a high backscattering regime in which switching is suppressed. In the latter case the photon statistics are similar to those of a single-mode standing wave dye laser.     

Ring-doped cladding-pumped single-mode three-level fiber laser

We propose and theoretically analyze three-level cladding-pumped fiber lasers in which the laser-active dopant is placed in a ring around a single-mode core. A ring-doped laser can work efficiently at wavelengths with strong small-signal absorption. This is otherwise difficult in a cladding-pumped fiber. Moreover, ring doping makes the laser less sensitive to quenching of the laser-active dopant and to excited-state absorption of the lasing field. In simulations of a Yb(3+) -doped fiber laser, ring doping increased the slope efficiency to 62%, up from 13% for a conventional core-doped fiber.     

Dynamical Properties of Two-Mode Ring Laser with Injected Signal

The dynamical properties of two-mode ring laser with different values of mode coupling constants are investigated by the full saturation laser theory with an injected signal. By a one-dimensional approximation, the intensity correlation time T_c and effective eigenvalue λ_eff¹¹ are calculated. The effects of backscattering and injected signal are discussed.     

A high-power single-mode cw dye ring laser

Due to spatial hole burning, standing-wave dye lasers require a large amount of selectivity inside the cavity for single-mode operation. The output power of these lasers is limited by losses caused by the frequency selecting elements. In a travelling-wave laser, on the other hand, spatial hole burning does not exist, thereby eliminating the need for high selectivity. A travelling-wave cw dye laser was realized by unidirectional operation of a ring laser, yielding single mode output powers of 1.2 W at 595 nm and of 55 mW in the UV-region with intracavity frequency doubling.     

Second-order interference of two independent and tunable single-mode continuous-wave lasers

The second-order temporal interference of two independent single-mode continuous-wave lasers is discussed by employing two-photon interference in Feynman's path integral theory. It is concluded that whether the second-order temporal interference pattern can or cannot be retrieved via two-photon coincidence counting rate is dependent on the resolution time of the detection system and the frequency difference between these two lasers. Two identical and tunable single-mode continuous-wave diode lasers are employed to verify the predictions. These studies are helpful to understand the physics of two-photon interference with photons of different spectra.     

A fiber micro-vibration sensor based on single-mode fiber ring laser

A new micro-vibration sensor based on single-mode fiber ring laser is put forward. The Mach-Zehnder interferometric （MZI） detection technique is presented for interrogating laser frequency shift due to the measurand （piezoelectric transducer （PZT） is used to simulate the micro-vibration） induced laser cavity strain from both single- and multi-mode lasers. In the experiment, compared with multi-mode laser sensors, the single-mode laser sensor is proved to be a sensor with high resolution. When the PZT is driven by the analog signal （0.03 rad near 2 kHz）, the signal-to-noise ratio （SNR） of output signal from the single-mode laser sensor is close to 55 dB and the sensitivity of the sensor is about 5 ×10^-5 rad/Hz1/2.     

Laser saturation grating phenomena

Spatial hole burning of population differences by standing waves is considered in terms of Bragg-like gratings. This philosophy is used to explain increased saturation in two-mirror, single-mode laser operation with stationary active systems, modified mode coupling in the corresponding two-mode operation, an intensity dip that might occur in flowed standing wave lasers, bistable unidirectional ring laser operation, and increased saturation in distributed feedback lasers. The analysis is developed for both stationary media and for those moving with respect to the standing wave. The latter treatment is used to interpret washout of grating contributions in Doppler broadened media, and to determine level decay constants in stationary media. This last application constitutes a stationary system analog to the Doppler medium's Lamb dip spectroscopy and can be called saturation grating spectroscopy. Knowledge of the decay constants is particularly important in laser studies involving coherent mode couplings such as due to saturation grating scattering and population pulsations. It is further shown that the same equations result for probe and saturating waves propagating in the same direction. One then obtains a signal absorption with a heterodyne advantage. Inasmuch as diffusion affects the two methods quite differently, this phenomenon should be easily examined. Work supported in part by a U.S. Senior Scientist Award (administered by the Alexander von Humboldt Stiftung) and in part by the Space and Missile Systems Organization, Los Angeles, California.