Theoretical study on temperature features of a sealed cesium vapor cell pumped by laser diodes

Abstract

The diode-pumped alkali laser (DPAL) is a new type of laser source which has been widely studied in the recent years. The temperature distribution of a sealed vapor cell, which is the crucial component in a DPAL system, produces an important effect on the output performance of a DPAL. In this paper, the strict solution of the heat conduction equation for a cesium vapor cell is obtained by using a finite difference procedure. The temperature distribution of a dummy open cell is first analyzed, and then the temperature distributions of two independent windows, regarded as the boundary conditions of solving a sealed cell, are evaluated in detail. By combining the results of the two steps together, we finally acquire the temperature distribution of a real sealed cesium vapor cell. The results reveal that the temperature gradients on both radial and longitudinal directions change with the pump power, cell radius, and absorption coefficient when the sealed cesium vapor cell is heated or pumped with the laser diodes. The conclusions are helpful for accurately evaluating the output characteristics of a DPAL.

Experimental evaluation of temperature distribution of a vapor cell using a Hilbert transform procedure

“…Based on the kinetic evaluation, Barmashenko et temperature distribution by assuming the temperature is a constant inside the lasing region [8] . Han et al have created an analytic system by considering both laser kinetics and heat transfer [9][10][11] . Shaffer has presented a new method to measure the temperature in a Cs cell, in which the simulation process is greatly dependent on a software called as QuickFringe [12] .…”

“…The concept of a diode-pumped alkali vapor laser (DPAL) was first proposed by Krupke in Lawrence Livermore National Laboratory (LLNL) at the beginning of the twenty-first century [1] . In the past decade, DPALs have been paid a lot of attention because of their advantages of high Stokes efficiency, good beam quality, compact size and near-infrared emission wavelengths [2–4] . However, the temperature inside the vapor cell in a DPAL system usually exhibits an inhomogeneous distribution due to the poor thermal conductivity of a gas-state medium.…”

Deleterious processes of a diode-pumped cesium vapor hollow-core photonic-crystal fiber laser

“…The oscillator of a DPAL usually contains an enclosed glass cell, in which the vapor of neutral alkali (K, Rb, Cs) and several kinds of buffer gases (helium and hydrocarbon with small molecular weight) are sealed with a certain pressure [4][5][6] . In 2006, Payne et al proposed a patent describing a new kind of DPAL in which a hollow-core photonic-crystal fiber (HC-PCF) is used as the vapor container [7] .…”

Algorithm for evaluation of temperature distribution of a vapor cell in a diode-pumped alkali laser system (part II)

“…However, the thermal effects will bring about some serious problems in nonuniformity of the temperature distribution for a high-powered DPAL system because the thermal conductivity of a gas-state medium is so small that the generated heat cannot be transferred outside efficiently [6][7][8][9]. Unlike a conventional electrically-excited gas-state laser, the number densities of alkali vapors and buffer gases (generally being helium and small hydrocarbons such as methane and ethane) in a DPAL often exhibit inhomogeneous distributions resulting from the temperature gradient inside a vapor cell [10].…”

“…Until now, only two research groups have referred the physical characteristics of a DPAL with a flowing approach. One is the team led by B. D. Barmashenko and S. Rosenwaks who have undertaken a series of fruitful studies on flowing-gas DPALs [9,[12][13][14][15]. The other is the team of National University of Defense Technology of China.…”