Efficient multi and single line atomic fluorine lasers

Intense multi- and single-line laser operation is reported from semiconductively preionised atomic fluorine lasers employing an optimised capacitor transfer excitation circuitry. The performance and spectral characteristics of these lasers are discussed and compared to the characteristics of previously described atomic fluorine lasers. The efficiency of one of these lasers described, at optimum conditions, is reaching a value as high as 0.14%. To the best of our knowledge, this is the highest efficiency reported up date, for an atomic fluorine laser.     

Temporal synchronization of independently tunable single longitudinal mode hybrid CO2 lasers

We report a quantitative study of temporal synchronization of two independently tunable, single longitudinal mode, hybrid CO₂ lasers, sharing a common high pressure section. The theoretical estimates for the dependence of the laser pulse build up time on the cw section pressure are in satisfactory agreement with the experimental results. Further, we show that temporal synchronization over a larger frequency range with no significant degradation of peak power or longitudinal mode selection is possible, by utilising the cw section gain length and cavity Q as additional control parameters.     

Resonance amplifier model describing diode lasers coupled to short external resonators

A model of a regenerative resonance amplifier has been used to describe Fabry-Perot GaAs diode lasers coupled to short external resonators. The optical gain and the equivalent input of the resonance amplifier are controlled by means of appropriate rate equations. Homogeneous line-broadening and proportionality between gain and electron density have been assumed in this approach. The model was applied to a diode laser coupled to an external plane mirror placed at a variable distance from one diode mirror. A numerical evaluation of the coupling coefficient between laser and external cavity enables to predict the measured power output and mode selective properties of the coupled system. A similar analysis was done for diode lasers coupled to external hemispherical resonators. The model calculation confirms the previously demonstrated mode selective properties of the hemispherical configuration which permitted stable single mode operation.     

A fast and precise three-dimensional measurement system based on multiple parallel line lasers

This paper conducts a trade-off between efficiency and accuracy of three-dimensional(3 D)shape measurement based on the triangulation principle,and introduces a flying and precise 3 D shape measurement method based on multiple parallel line lasers.Firstly,we establish the measurement model of the multiple parallel line lasers system,and introduce the concept that multiple base planes can help to deduce the unified formula of the measurement system and are used in simplifying the process of the calibration.Then,the constraint of the line spatial frequency,which maximizes the measurement efficiency while ensuring accuracy,is determined according to the height distribution of the object.Secondly,the simulation analyzing the variation of the systemic resolution quantitatively under the circumstance of a set of specific parameters is performed,which provides a fundamental thesis for option of the four system parameters.Thirdly,for the application of the precision measurement in the industrial field,additional profiles are acquired to improve the lateral resolution by applying a motor to scan the 3 D surface.Finally,compared with the line laser,the experimental study shows that the present method of obtaining 41220 points per frame improves the measurement efficiency.Furthermore,the accuracy and the process of the calibration are advanced in comparison with the existing multiple-line laser and the structured light makes an accuracy better than 0.22 mm at a distance of 956.02 mm.     

On the tunable infrared gas lasers

The high-pressure (≈ 10 atm) electrically excited molecular gas lasers with full overlapping of the rotational lines caused by high-pressure broadening are considered as a possible new type of the powerful infrared lasers with tunable frequency. For CO₂ - laser the overlapping occurs at pressures 10 ≈ 15 atm. It is experimentally shown that the transverse-excitation multiple-arc technique allows laser action at gas pressures up to 1.8 atm for CO₂ and ≈ 0.9 atm for HF-lasers.     

Refractive-index saturation-mediated multiple line emission in polymer thin-film distributed-feedback lasers

We report experimental and theoretical investigations of multiple laser-line emission in a distributed-feedback dye laser pumped by two coherent optical beams. We have used a Lloyd interferometer configuration with second- and third-order Bragg reflections to study the interaction between the two incident pumps in an organic thin film. We demonstrated theoretically that the number of laser emission lines can be interpreted with reference to the saturation effect in the refractive index.     

远红外可调谐喇曼激光器理论

本文用缀饰原子方法解出四能级系统远红外激光增益系数的解析表达式。结果表明,远红外增益谱一般由四个共振峰组成,取合适的失谐量,可能得到两个正的增益极大,并分别对应于喇曼增益和线中心增益。     

Pure single line oscillation of HF lasers in fine atmospheric window

Applied Physics B - A correction to this paper has been published: https://doi.org/10.1007/s00340-021-07611-y     

Frequency stabilized and tunable multimode He-Ne lasers

A simple modified technique for stabilizing an internal mirror multimode laser has been experimentally studied. The laser was locked with respect to different points on the gain curve. Lasers with different types of polarization configurations have been stabilized and short-term variations of about 2 MHz and a long-term drift of ±5 MHz over a period of two hours have been observed.     

A two dimensional theoretical model for describing gain coefficient in N2-lasers and the model validity for CVL and excimer lasers

Based on our previously reported measurements on the gain-value in a N₂- laser and numerical calculations, we introduce a method to obtain an analytical expression for the small signal gain, g₀, where the dependency of g₀ on the laser geometrical configuration, including electrodes length and gap separation, is demonstrated. For this study one- and two-dimensional approaches for the photon density have been applied independently to determine gain-parameter, where for explaining the observed dependency of the gain-parameter on the laser electrodes separation, d_AMP, which was found experimentally and explained by an empirical expression of the type g₀ = r + q/d_AMP, with r and q some constants, realization of introducing an extra dimension along the gap separation was unavoidable. For the electrodes length, l_AMP, we have already shown that an empirical equation of the type g₀ = m + n/l_AMP, with m and n some constants, is consistent with the measurements corresponding to N₂-lasers. With this realization, it is proved that the gain-parameter in N₂-lasers can be written as g₀^{above threshold} = m″ + g_0z(γ_L^z, z) + g_0y(γ_L^y, y), where it consists of two independent gain-values along the electrodes length (z) and gap separation (y) with the corresponding power losses given by γ_L^z and γ_L^y. m″ is a very small quantity showing that laser is operating slightly above the threshold. The results of this calculation are consistent with our recent measurements and also other reported N₂-laser gain values measured under moderate current density conditions. To check the validity of the model for other types of lasers, the reported gain-values for copper vapor lasers of different laser tube radii, R_AMP, and tube lengths, l_AMP, have been examined using the one-dimensional model of either g₀(R_AMP) or g₀(l_AMP) and the consistency with the observed measurements was found to be quite satisfactory. The model was also found to be valid for the excimer lasers of different types, different gas mixtures and pressures at a constant input operational voltage. Due to limited numbers of the reported experimental measurements, for the graphs preparation of g₀(l_AMP) in excimer lasers we used the observed data at V₀ = 30 kV and also some variations of the input voltages in the range of ΔV ≅ 20 kV have been adopted. The results for both cases were found to be consistent with the proposed one-dimensional model.     

A tunable magnetically insulated transmission line oscillator

A tunable magnetically insulated transmission line oscillator(MILO) is put forward and simulated. When the MILO is driven by a 430 k V, 40.6 k A electron beam, high-power microwave is generated with a peak output power of 3.0 GW and frequency of 1.51 GHz, and the relevant power conversion efficiency is 17.2%. The 3-d B tunable frequency range(the relative output power is above half of the peak output power) is 2.25–0.825 GHz when the outer radius of the slow-wave structure(SWS) vanes ranges from 77 mm to 155 mm, and the 3-d B tuning bandwidth is 92%, which is sufficient for the aim of large-scale tuning and high power output.     

Semiconductor lasers and Kolmogorov spectra

We make a prima facie case that there could be distinct advantages to exploiting a new class of finite flux equilibrium solutions of the quantum Boltzmann equation in semiconductor lasers.     

Automatically tunable second-harmonic generation of dye lasers

A new technique which realizes the phase-matching of second harmonic generation (SHG) over a wide spectral range without mechanical or temperature tuning of the SHG crystal is developed. The phase-matching is achieved by changing the angle of the laser beam incident on the SHG crystal using dispersive components such as gratings or prisms. Over the entire spectral range of a Rhodamine-6G dye laser, the phase-matching is realized with a KDP crystal using this technique. This system is capable of producing tunable coherent ultraviolet light from 2300 Å to 3500 Å with an extremely fast scanning rate, if the dispersion of the prism and the SHG crystal is carefully matched.     

Spectroscopic measurements of the stratosphere using tunable infrared lasers

Measurements of temporal variation of stratospheric NO are important in validating its postulated role in catalytic destruction of stratospheric ozone. This paper reviews the results of NO measurements obtained from the two recent balloon-borne spin-flip Raman laser opto-acoustic spectroscopy experiments. The temporal variation of NO reported here strongly supports the role of NO in the stratospheric O₃ balance. The paper compares the results obtained here with those obtained using different techniques. Also are compared the relative merits of the various techniques. Future improvements in the present technique as well as other possible experimental stratospheric studies are considered.     

A new approach for dynamic modeling of widely tunable GCSR lasers

A new dynamic model is developed for simulating the widely tunable grating assisted codirectional coupler with rear sampled grating reflector （GCSR） lasers. The gain section of the device is calculated in timedomain using traveling-wave method, while the transmission spectrum of the coupler and the reflection spectrum of the reflector are firstly simulated in frequency-domain, and then transformed into time-domain via digital filter approach. Both static and dynamic performances based on this model agree well with the published results. Compared with previous works, this new model is more efficient and applicable, especially in the dynamic simulation.     

一个描述合作网络顶点度分布的模型

讨论一类社会合作网络以及一些与其拓扑结构相似的技术网络的度分布.建议一个最简化模型，通过解析的方法说明这些网络演化的共同动力学机理，而且说明顶点的度分布和项目度分布之间具有密切的一致关系，而项目所含的顶点数分布对度分布的影响较小；对模型的更一般情况进行数值模拟，说明上述结论具有一定的普遍性.这个模型显示这类广义的合作网络一般具有处于幂函数和指数函数这两种极端情况之间的度分布.简要介绍对一些实际合作网络做统计研究的结果，说明本模型的合理性. 关键词： 合作网络 度分布 项目度分布 项目含顶点数