A magnetically stabilized coaxial laser discharge

A new magnetic discharge stabilization technique for coaxial laser systems is described. The approach utilizes crosses electric and magnetic fields to create and maintain a large and rapidly rotating plasma volume which does not experience glow-to-arc transitions. Very high cw specific discharge power loadings have been achieved even without the benefit of external gas cooling or circulation.Performance is insensitive to gas composition and pressure such that high power coaxial discharges have been run in CO₂ laser gas mixtures up to several hundred torr. Stable cw discharges have also been obtained in mixtures containing several torr of SF₆.The technique appears to be readily scalable to give very large excited volumes in systems with comparatively small overall physical dimensions.     

Self-locked He-Ne ring laser

Experimental conditions necessary for self-pulsing to occur in a He-Ne ring laser are reported. These results are compared with predictions that are based upon theoretical models that have been presented in the literature. Good qualitative agreement is found in that theory and experiment both show that self-pulsing will only occur over a range of excitation. Quantitative results differed enough to indicate that additional refinement is needed even though the models have identified many of the important parameters involved.Supported by the US Army Research Office.     

Simple single-frequency He-Ne laser

For a (0.5–0.6)m long He–Ne laser tube, single longitudinal mode 632.8 nm generation is obtained, using a higher gas-mixture pressure and application of an axial magnetic field. An efficient and very simple mode selection is obtained by gas-mixture pressure increase only. A multimode power to single-mode power conversion coefficientk=0.75 is obtained by increasing the tube pressure. A further increase tok=0.85 is possible with optimum magnetic field and gas pressure.     

He-Ne laser wavelength-shifting interferometry

The use of wavelength-shifting interferometry with a He-Ne laser source is presented. The approach is based on the thermal expansion of the laser cavity during the warm-up time, in conjunction with an unequal path interferometric configuration. The optics principles are reviewed, and a demonstrative measurement is presented. The technique extends the capability of phase-shift acquisition and processing to cases where conventional methods with piezoelectric transducers cannot be used, and particularly to external measurement cavities of large diameter.     

General relativistic razor-thin disks with magnetically polarized matter

The origin of magnetic fields in the universe still remains unknown and constitutes one of the most intriguing questions in astronomy and astrophysics. Their significance is enormous since they have a strong influence on many astrophysical phenomena. In regards of this motivation, theoretical models of galactic disks with sources of magnetic field may contribute to understand the physics behind them. Inspired by this, we present a new family of analytical models for thin disks composed by magnetized material. The solutions are axially symmetric, conformastatic and are obtained by solving the Einstein–Maxwell Field Equations for continuum media without the test field approximation, and assuming that the sources are razor-thin disk of magnetically polarized matter. We find analytical expressions for the surface energy density, the pressure, the polarization vector, the electromagnetic fields, the mass and the rotational velocity for circular orbits, for two particular solutions. In each case, the energy–momentum tensor agrees with the energy conditions and also the convergence of the mass for all the solutions is proved. Since the solutions are well-behaved, they may be used to model astrophysical thin disks, and also may contribute as initial data in numerical simulations. In addition, the process to obtain the solutions is described in detail, which may be used as a guide to find solutions with magnetized material in General Relativity.     

Observation of radiation instabilities of a two-mode He-Ne laser with the help of interference of polarized rays

Instabilities in the operation of a two-mode He-Ne laser are observed with the help of interference of polarized beams. Two interference patterns created by two radiation modes alternatively appear. The contrast of the interference pattern increases under the action of an external constant magnetic field on the laser. If one of the interfering beams is delayed sufficiently long, the instability manifests itself in the motion of interference fringes in a direction that depends on which of the two beams is delayed. The particular features of the evolution of the interference pattern are explained based on interference equations for the two modes that take into account the orthogonality of the linear polarizations of the modes, as well as changes in their amplitudes and frequencies.     

He-Ne laser pumped dimer lasers

Continuous laser oscillation of the dimer molecules Na₂, K₂ and I₂ on more than 40 lines in the spectral range of 685 nm to 1170 nm has been obtained by optical pumping with a He-Ne laser of up to 25 mW output power. Thresholds as low as 1 mW and output powers up to 1.5 mW could be achieved. Properties of these simple optical conversion system will be discussed.     

611.8 nm single-mode He-Ne laser

The conditions for optimum 611.8 nm laser operation are obtained and a convenient method for indicating 3.39 µm suppression is proposed. Single longitudinal mode 611.8 nm generation is obtained using higher gas-mixture pressure and application of an axial magnetic field. Several milliwatt monomode output power and 0.75 multimode-to-monomode power conversion coefficients are obtained without an internal iodine cell. A comparison of the experimental results with a single-mode laser theory is given.     

Inexpensive He-Ne laser tube construction

The construction and processing of a low power He-Ne laser tube is described. The tube uses the least expensive construction materials and is applicable to mass production fabrication methods. A cost analysis is presented.     

Frequency up-conversion He-Ne laser without inversion

A scheme for obtaining up-conversion lasing without inversion in the visible range is proposed using a Doppler-broadened He-Ne mixture as active medium. We consider a cascade scheme (2s₂2p₂1s₃) with a frequency up-conversion ratio of 1.91. The upper transition is inverted and driven by an external field and lasing without inversion occurs at 616.4 nm provided that the collisional decay rates of the 1s₃ and 1s₅ levels overcome a certain threshold. PACS 42.50.Gy; 32.80.Qk; 42.70.Hj     

Intermittent frequency offset lock of a symmetric three-mode stabilized He-Ne laser to an iodine stabilized He-Ne laser

There is a need for an intense, unmodulated single-frequency stabilized laser light that guarantees absolute optical frequency in a rapid laser calibration or an ultra-high resolution interferometer. To obtain such a light, we developed a new laser system that uses an intermittent frequency offset lock of a symmetric three-mode stabilized He-Ne laser to an iodine stabilized He-Ne laser. The proposed laser system provides two operational modes: (1) independent and (2) slave mode. In the independent mode, frequency of the three-mode laser is stabilized via control of frequency difference between two intermode beats. The resultant output is a single longitudinal mode light of maximum intensity that locates at the top of the gain curve. Frequency instability of 8X10^-12 (at a sampling time of 100 s) which is better than conventional stabilized lasers is attained in the independent mode. Slow optical frequency drift during the independent mode is periodically corrected by the offset lock to the iodine stabilized laser (slave mode), resulting in accurate reset of the frequency drift. After reset of the frequency deviation, the three-mode laser is again operated in the independent mode. Due to such intermittent offset lock, duty factor of the iodine stabilized laser was reduced to a few % of continuous operation.     

A technique for frequency stabilization of an internal mirror He-Ne laser

A technique for frequency stabilization of an internal mirror He-Ne laser using phase sensitive detection without cavity length modulation is suggested. The orthogonally plane polarized modes are separated and then convered into two photoelectric signals using two photodetectors. The photoelectric signals are switched alternately so as to generate a square wave, whose amplitude is proportional to the intensity difference between the two orthogonal polarizations. A lock-in amplifier is used to detect this square wave, with the switching frequency as reference. The phase detected signal is used for thermal stabilization of the laser. The frequency stability of 5 × 10⁻⁹ was obtained with an integration time of 1 s.     

半内腔He-Ne激光器的调整技巧

介绍了半内腔式He-Ne激光器的结构及调整的技巧,测量了在不同放电电流以及不同腔长条件下激光器的输出功率,得到了最佳的放电电流. 半内腔式He-Ne激光器的应用,有助于学生了解激光器的工作物质、谐振腔等主要组成部分,也促进了学生对激光理论的进一步理解.     

外腔式氦氖激光器的因斯高斯光束产生方法

提出了一种从外腔式氦氖激光器平凹谐振腔腔内产生光强分布具有椭圆对称性的因斯高斯光束(InceGaussian Beams,IGBs)的方法。利用3.5mm大毛细管直径的放电管,通过轻微调节放电管俯仰角和球面反射镜来打破谐振腔的对称性,可得到丰富的高斯模式和较好的IGBs光场分布图,与理论计算图对比具有较好的一致性。     

Mode-locked He-Ne laser pulse compression and expansion

By means of an electro-optic internal modulator it is possible to obtain from a laser He-Ne recurring pulses whose duration (about 500 psec) is the inverse of the Ne amplifying spectral bandwidth. The optical frequency of these pulses, passing through an external modulator is translated or linearly modulated. The duration of the linear frequency modulated pulses, whose spectrum is widely broadened, is then reduced by travels into a dispersive interferometric structure (optical dispersive delay line). A pulse compression ratio at least equal to 3 has been obtained.     

峰值稳频横向塞曼He—Ne激光器

本文主要介绍一种峰值稳频横向塞曼He-Ne激光器。实验发现激光器输出相互垂直振动的光拍频频率的最大值对应激光器增益轮廓中心。利用调制的方法将激光器输出激光的频率稳定在增益轮廓中心。与国家计量测试研究院的碘吸收稳频标准激光器拍频,频率稳定度为1×10~(-9)。