A highly feasible full-field phase-measuring methodology has been developed to investigate the phase distortions of a probe beam transmitting through a LiB3O5 (LBO) crystal under different conditions. The results show that wavefront phase exhibits inhomogeneous distribution when the crystal is heated and the phase difference becomes small as time goes by when the heating temperature is kept unchanged. The technique provides an easy and feasible way to accurately measure the phase images of a probe beam transmitting through a crystal. The procedure provided in this report can be also used to study the rapid phase changes that take place in other types of optical materials.
A master oscillator power amplifier (MOPA) is thought to be a suitable equipment to realize the power scaling for a diode pumped alkali laser (DPAL). In fact, the characteristics of a DPAL-MOPA system strongly depend on the central wavelengths of both a seed laser and a pump laser due to the extremely narrow nature linewidth for atomic alkali. In this report, a theoretical model of an end-pumped DPAL-MOPA system is first developed to study the influence of deviations in central wavelengths on the output features. Then, the relationship between the environmental parameters and the output linewidth as well as the output power is analyzed. The results reveal that the deviation in central wavelengths of both a seed laser and a pump LD will lead to a dramatic decrease of the output power for a DPAL-MOPA system. The conclusions are thought to be helpful for design of an end-pumped DPAL with high powers.
In the recent years, alkali vapor lasers have become the most promising candidates for realization of a light source with both good beam quality and high output power because of their excellent performances. A rubidium laser is a typical kind of alkali vapor lasers. In this study, we developed a theoretical mode to evaluate the population densities of three levels as well as mode-matching efficiency of a rubidium laser pumped by a narrow-linewidth Ti:Sapphire laser under two different focal conditions. In the evaluation, at least two values of the output power of a rubidium laser must be known, which are usually obtained from the experiment. We performed a series of experiments by using two pump lenses with two focal lengths of 150 and 200 mm, and acquired two corresponding values of the laser output power. Then, we applied the experimental results in the theoretical calculation and then obtained the population densities of three levels and mode-matching efficiency of the rubidium laser. The study demonstrates that the outputted pump power can be used for evaluation of the population densities of three levels and mode-matching efficiency of an alkali laser under the different experimental conditions. The study might be valuable to better understand the physical features of an alkali vapor laser and to optimize the configuration of a high-powered alkali laser in the future.
Diode-pumped alkali lasers (DPALs) have attracted a lot of attentions in the recent years for their high Stocks efficiency, good beam quality, compact size and near-infrared emission wavelengths. In this study, we analyze the thermally-induced lens in an end-pumped cesium cell by using the evaluated parameters such as the population density distribution, the transition rates of pump photon absorption, and the transition rates of laser photon emission, which had been obtained in our previous study. After dividing a cylindrical vapor cell into many cylindrical annuli, we calculate the refractive index n and the thermal-optic coefficient dn/dT in every annule. And then, we carry out the ray-trace to describe the propagation of an incident ray inside the vapor cell. Assuming that the incident plane-wave has a flat-top distribution, the intensity distribution of the outputted beam can be deduced. We adopted the second-moment calculation to evaluate the beam size after the ray passes through a pumped cell. Finally, the effective focal length of a thermally-induced lens was obtained for the end-pumped laser configuration. The research will be helpful to improve the beam quality of a DPAL.
Diode-pumped alkali lasers (DPALs) have gained rapid development in the recent years due to their great potential for realization of high-power lasers. Relaxation oscillation (RO) is a common phenomenon related to the dynamic process in time domain. Generally, the generation of spikes in RO may affect the output stabilization of a DPAL. In this paper, we develop a kinetic model to investigate the output characteristics in time domain. Using such a mathematical model, a comparative study on the RO features of a diode-pumped rubidium vapor lasers (DPRVL) and a diode-pumped cesium vapor lasers (DPCVL) is theoretically carried out with different physical parameters including the cell temperature, buffer gas pressure, pumping power and reflectance of an output coupler. The analyses should be valuable for design of a steady high-powered DPAL.
A diode-pumped alkali laser (DPAL) provides the significant promise for high-powered performances. For an end-pumped DPAL, both the absorption and the lasing distribution crucially affect the output physical features. In this report, a mathematical model is introduced for examining the absorption and lasing processes of the gas-state media by using a segmental approach. The energy transmission inside the oscillator has been theoretically analyzed for construction of a reciprocating regime which is based on the self-consistency principle. Basically, the conclusion can be extended to any end-pumped laser configurations.
In recent years, reflecting volume-Bragg-gratings (RVBGs) have been considered as the perfect elements to narrow the spectrum with highly adjustable parameters. In fact, the effects of narrowing the linewidth of high-powered LDs are determined by the parameters such as the grating thickness, refractive index modulation, and grating spatial frequency. By use of the theoretical regime, the relationships between the effective diffraction efficiency and these parameters of a RVBG have been systematically investigated to narrow the linewidth to a desired value. Although the results reveal that a higher effective diffraction efficiency may be achieved by adopting three parameters mentioned above with higher values, by considering the difficulties and confinement in production process of a RVBG, the characteristic parameters should be carefully selected as some appropriate values. From the evaluation, one also understands that the narrow linewidth of a RVBG-coupled LD and the high effective diffraction efficiency cannot be arbitrarily realized at the same time for a real case. The conclusions are thought to be valuable in construction of a practical narrow linewidth LD system.
In recent years, a diode-pumped alkali laser (DPAL) has become one of the most hopeful candidates to achieve the high power performance. A series of models have been established to analyze the DPAL’s kinetic process and most of them were based on the algorithms in which only the ideal 3-level system was considered. In this paper, we developed a systematic model by taking into account the influence of excitation of neutral alkali atoms to higher levels on the physical features of a static DPAL. The procedures of heat transfer and laser kinetics were combined together in our theoretical model. By using such a theme, the continuous temperature distribution has been evaluated in the transverse section of a cesium vapor cell. The calculated results indicate that the excitation plays an important role during the lasing process, which might deepen the understanding of the kinetic mechanism of a DPAL.
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