Back-reflection effects in a frequency-stabilized two-mode He-Ne laser

We investigated the behavior of a frequency-stabilized 1 mW two-mode helium-neon laser in the presence of optical feedback. In this paper, we presented how the amplitude and frequency shift of the returning beam influence operation of the laser. We showed the conditions under which the He-Ne laser work is unstable and stable in frequency and where it is insensitive to the returning beam. We also showed how much the frequency of the returning beam has to be shifted in order to reduce the sensitivity of the laser on the back-reflection.     

Tapered Bragg reflection waveguide edge emitting lasers with near circular twin-beam emission简

Experiments on developing a frequency-stabilized 555.8-nm laser are presented. The 555.8-nm laser＇ is obtained by frequency doubling of a l lll.6-mn diode laser through single-passing a periodically poled lithium niobate （PPLN） waveguide. Tile 555.8-nm laser is then locked to a stable high-finesse Fabry Perot （FP） cavity by tile Pound Drever--Hall （PDH） technique. Tile finesse of the cavity is measured by tile heterodyne cavity ring-down spectroscopy technique. The linewidth of the 555.8-nm laser is investigated. Alter the laser is locked, the laser line width is reduced to about 3 kHz. This frequency-stabilized 555.8-nm laser is used in experiments on the laser cooling and trapping of ytterbium atoms to develop an ytterbium optical clock.     

Erratum to: Allan-variance measurements of diode laser frequency-stabilized with a thin vapor cell

A novel method of stabilizing laser frequency that uses a sub-Doppler spectrum of atoms in a thin vapor cell has been developed. The extended-cavity diode laser is frequency-locked to a hyperfine component of the Cs D₂ line. The linewidth and the signal-to-noise ratio of the spectrum are systematically investigated to find a cell length that gives best long-term frequency stability. In the Allan-variance measurements on the beat note between two lasers thus stabilized, a frequency stability of 6.2×10^-11 is achieved at an averaging time of 5 s. PACS 42.62.Fi, 42.60.Lh, 39.30.+w     

Iodine stabilized He-Ne laser with a hot wall iodine cell

We describe experiments we have done with a hot wall iodine cell He-Ne laser. The net result is an improvement of the contrast of the saturated absorption peak which is used for frequency stabilization. The frequency shifts induced by collisions are measured. Anomalous modulation width dependent frequency shifts are observed in some cases.     

An intermittent frequency offset lock of a transverse Zeeman laser to an iodine stabilized He-Ne laser

A single-mode frequency stabilized laser with modulation-free and moderate power is desired as a light source for an ultra-high resolution interferometer system and/or a rapid laser calibration system. For this purpose, we developed a new stabilized laser system that utilizes intermittent control of a 2 mW transverse Zeeman stabilized He-Ne laser (Zeeman laser) with an iodine stabilized He-Ne laser (I2 stabilized laser). Because of the intermittent control, working time of the I2 stabilized laser is reduced. The Zeeman laser has two operational modes: independent and slave mode. In the independent mode, the Zeeman laser is stabilized through control of Zeeman beat frequency. Temperature dependent drift of the oscillation frequency during the independent mode is periodically corrected by the slave operation utilizing frequency offset locking to the I2 stabilized laser. Frequency instability of the Zeeman laser in independent and slave modes is 7.7X10-11 and 2.0X10-11, respectively, at the sampling time of 100 s.     

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.     

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.     

氦氖激光器稳定性测试及功率谱分析

在使用氦氖激光的一些测试系统或控制系统中，氦氖激光的时间稳定性直接影响着测试的精度和控制的稳定性。为了提高系统测试精度或消除控制中的振荡，就必须了解氦氖激光器输出信号的强弱变化和它们的频谱。本文提出了一种氦氖激光器稳定性的测试方案。作者结合科研课题采用这一方案进行了多次内场和外场实验，利用微机进行数据采集，得到了多组激光输出强度随时间变化的数据，且编制了应用软件用极大熵法对采集的结果进行了频谱特性分析。文中给出了若干组测试结果曲线和相应的功率谱曲线。并对这些曲线进行了分析，得出了一些符合实验的结论，提出了若干改进的意见，已经得到了有关单位的采纳。     

Doppler-free two-photon excitation of nitric oxide with frequency-stabilized cw dye laser radiation

Doppler-free two-photon transitions are induced in nitric oxide with blue, narrowband, tunable radiation generated by a frequency-stabilized cw dye ring laser. The recorded two-photon spectra provide a precise measurement of the spin-rotation splitting of the excited rotational levels (A ²∑⁺, ν' = 0) N' = 1 to N' = 19. The splitting constant γ is determined to be γ = 80.35(15) MHz.     

Stability of two-mode oscillations in a He-Ne laser

Journal of Applied Spectroscopy -     

Sputtering the surface of a He-Ne laser cathode

The results from analyzing the surface of an aluminum cathode by means of atomic force microscopy (AFM) and Auger electron spectroscopy (AES) are presented. Cathode surface sputtering is simulated via the Monte Carlo method using the SRIM program. Factors affecting the formation of the surface relief of cold cathodes under the action of bombarding ions are discussed along with the main mechanisms of surface modification and ways of enhancing the stability of the material with respect to the action of ions.     

A magnetically polarized He-Ne laser

The performance of an internal mirror He-Ne laser that has a fraction of its capillary immersed in a strong transverse magnetic field will be described. The field is produced by permanent magnets which are built into the laser's housing. The laser produces a light output which has less than 0.1% of its power in the modes polarized orthogonal to the magnetic field. The attainment of such a high degree of polarization requires that the magnetic field be oriented relative to naturally occuring anisotropies of the laser cavity. Misalignment not only lowers the degree of polarization, but also decreases the laser's output.     

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.     

Measurement of liquid surface properties using a He-Ne laser

The surface tension, viscosity, and damping coefficient of surface waves on a liquid sample have been determined by observing the diffraction of an optical beam. To achieve high accuracy, a He-Ne laser having a high brightness and coherence was used as a light source. Experiments illustrating and verifying the techniques are described.Values of the surface tension for different samples have been measured with a standard deviation of less than ±0.6% for frequencies of the ripple motion ranging from 500 to 3 000 Hz over the temperature range 20–45°C. The viscosity and damping coefficient of water were measured for frequencies in the range 600–1500 Hz. The values obtained agree with those available from the literature.