Diode pumped alkali laser (DPAL) with hydrocarbon buffer gases has the features of low threshold and high efficiency. The chemical reaction between alkali and hydrocarbon gases affects the life time of DPAL. In this paper, a method based on Fourier transform infrared spectroscopy and Lambert-Beer law is adopted to find a safe temperature at which DPAL runs for a long term. A theoretical model is established to figure out ways to reduce the peak temperature in the cell window. The results indicates that 170 °C is a safe temperature. Although the absorbance of the cell window to the pump light and alkali laser is lower, there is temperature increase. Small light-transmitting area and air blowing on the windows can reduce the peak temperature effectively. Cooling the cell window is essential and critical in a long-term running DPAL.
A continuous wave diode pump rubidium vapor laser (Rb-DPAL) is developed in this paper. It has long operating time at output power of 1 W. The Rb-DPAL, with optical efficiency of 18.9% and slope efficiency of 24.0%, has the characteristics of high stability and good beam quality. It is expected to be a kind of good pump source of SERF rubidium magnetometer.
A self-heated diode-pumped alkali laser (SDPAL) with a microfabricated alkali cell is proposed. Based on Beach’s model and finite-element analysis theory, the output characteristics of a cesium self-heated laser are studied. The results indicate that an SDPAL with a cell length of 2 mm is feasible. The output power of a typical SDPAL is ∼Watt level. Rapid heat convection around the mini cell can increase the output power. At the same time, the utilization ratio of the pumping light will decrease. A heating experiment is also conducted to validate the theoretical model. When pumping power of 0.69 W is illuminated on the light absorber, the cell temperature can reach 76.4°C with a single-side heated structure. The results show that with a mini vapor cell, SDPAL can be portable and competitive when ∼Watt-level laser with wavelength of alkali D1 line is required.
A theoretical model based on common pump structure is proposed to analyze the output characteristics of a diode-pumped alkali vapor laser (DPAL) and XPAL (exciplex-pumped alkali laser). Cs-DPAL and Cs-Ar XPAL systems are used as examples. The model predicts that an optical-to-optical efficiency approaching 80% can be achieved for continuous-wave four- and five-level XPAL systems with broadband pumping, which is several times the pumped linewidth for DPAL. Operation parameters including pumped intensity, temperature, cell’s length, mixed gas concentration, pumped linewidth, and output coupler are analyzed for DPAL and XPAL systems based on the kinetic model. In addition, the predictions of selection principal of temperature and cell’s length are also presented. The concept of the equivalent “alkali areal density” is proposed. The result shows that the output characteristics with the same alkali areal density but different temperatures turn out to be equal for either the DPAL or the XPAL system. It is the areal density that reflects the potential of DPAL or XPAL systems directly. A more detailed analysis of similar influences of cavity parameters with the same areal density is also presented.
A theoretical model based on common pump structure is proposed to analyze the laser output characteristics of DPAL (Diode pumped alkali vapor laser) and XPAL (Exciplex pumped alkali laser) in this paper. The model predicts that an optical-to-optical efficiency approaching 80% can be achieved for continuous-wave four- and five-XPAL systems with broadband pumping which is several times of pumped linewidth for DPAL. Operation parameters including pumped intensity, temperature, cell’ s length, mixed gas concentration, pumped linewidth and output mirror reflectivity are analyzed for DPAL and XPAL systems basing on the kinetic model. The result shows a better performance in Cs-Ar XPAL laser with requirements of relatively high Ar concentration, high pumped intensity and high temperature. Comparatively, for Cs-DPAL laser, lower temperature and lower pumped intensity should be acquired. In addition, the predictions of selection principal of temperature and cell’s length are also presented. The conception of the equivalent “alkali areal density” is proposed in this paper. It is defined as the product of the alkali density and cell’s length. The result shows that the output characteristics of DPAL (or XPAL) system with the same alkali areal density but different temperatures turn out to be equal. It is the areal density that reflects the potential of DPAL or XPAL systems directly. A more detailed analysis of similar influences of cavity parameters with the same areal density is also presented. The detailed results of continuous-wave DPAL and XPAL performances as a function of pumped laser linewidth and mixed gas pressure are presented along with an analysis of influences of output coupler.
Thermal control of the volume Bragg grating (VBG) in the LD with the external cavity is critical for the tuning of the wavelength and the narrowing of the bandwidth. Based on finite element theories, thermal properties of the VBG were researched under different conditions of LD illumining area, laser power, gratings’ working temperature and heat convection. Both the VBGs in the external cavity of LD bar and LD stack were considered in the experiments. The results show that higher working temperature of the VBG and adopting better heating convection cooling methods is beneficial to realize the uniformity of the VBG temperature distribution.
Thermal control of the volume Bragg grating (VBG) in the laser diode (LD) with the external cavity is critical for the tuning of the wavelength and the narrowing of the bandwidth. Based on finite element theories, thermal properties of the VBG were researched under different conditions of the LD illuminated area, laser power, gratings’ working temperature, and heat convection. Both the VBGs in the external cavity of the LD bar and stack were considered in the experiments. The results show that higher working temperature of the VBG and adopting better heat convection cooling methods are beneficial to realize the uniformity of the VBG temperature distribution.
We report a quasi-CW linearly-polarized rubidium vapor laser. The pumping source consists of 5 laser diode bars and its linewidth is reduced from the raw 1.8 nm to 0.2 nm by a bulk Volume Bragg Grating (VBG). Instead of adopting the “quasi-waveguide structure” gain cell, the pumping light of the rubidium vapor laser propagates freely in the vapor cell. The pumping light with polarization perpendicular to one of the rubidium laser is coupled into the resonator cavity by the PBS. Output power of 10 W with good beam quality is realized. This laser configuration is suitable for a convection-cooling DPAL.
We report a quasicontinuous wave (CW) linearly polarized rubidium vapor laser. The pumping source consists of five laser diode bars and its linewidth is reduced from the raw 1.8 to 0.2 nm by a bulk volume Bragg grating. Instead of adopting the “quasi-waveguide structure” gain cell, the pumping light of the rubidium vapor laser propagates freely in the vapor cell. The pumping light with polarization perpendicular to one of the rubidium laser is coupled into the resonator cavity by the polarized beam splitter. This laser configuration is suitable for a convection-cooling diode-pumped alkali vapor laser.
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