Abstract
The lifetime of Diode-Pumped Alkali Lasers (DPALs) is limited by damage initiated by reaction of the glass envelope of its gain medium with rubidium vapor. Rubidium is absorbed into the glass and the rubidium cations diffuse through the glass structure, breaking bridging Si-O bonds. A damage-resistant thin film was developed enhancing high-optical transmission at natural rubidium resonance input and output laser beam wavelengths of 780 nm and 795 nm, while protecting the optical windows of the gain cell in a DPAL. The methodology developed here can be readily modified for simulation of expected transmission performance at input pump and output laser wavelengths using different combination of thin film materials in a DPAL. High coupling efficiency of the light through the gas cell was accomplished by matching the air-glass and glass-gas interfaces at the appropriate wavelengths using a dielectric stack of high and low index of refraction materials selected to work at the laser energies and protected from the alkali metal vapor in the gain cell. Thin films as oxides of aluminum, zirconium, tantalum, and silicon were selected allowing the creation of Fabry-Perot optical filters on the optical windows achieving close to 100% laser transmission in a solid optic combination of window and highly reflective mirror. This approach allows for the development of a new whole solid optic laser.
Highlights
DIODE PUMPED ALKALI LASERSA diode pumped alkali lasers (DPAL) is a hybrid laser, which combines the best of both electric and chemical lasers to improve efficiency, cost and size
DPAL laser systems are of great interest due to their scalability and high quantum efficiency, 95.3% for cesium (Cs), 98.1% for rubidium (Rb), and 99.6% for potassium (K), versus 76% for a 1064 nm Nd:YAG solid-state laser.[1]
An Fabry-Perot resonator (FPR) behaves like a single L-layer at the design wavelength λ0
Summary
A DPAL is a hybrid laser, which combines the best of both electric and chemical lasers to improve efficiency, cost and size. The hypothesis is, that highly-amorphous thin film of oxides of zirconium, tantalum, titanium and aluminum has the potential to limit chemical reactions as well as absorption and diffusion of the rubidium into a fused silica substrate in a DPAL because of their electronic and thermodynamic properties These optical quality thin films, when combined with a multilayer dielectric stack of high and low index optical materials, may be designed to achieve high-optical transmission at input pump and output laser wavelengths. If a high and low index of refraction thin film materials are chosen, we can design a Fabry-Perot filter with the quarter-wave layer L sandwiched between the mirrors A/R|G|(HL)2L(HL)1|H| and thin film of damage-resistant optical material. Various combinations of selected optical materials and laser optical are shown in Table I: Figure 3 shows Matlab simulation of laser % optical power transmission vs. input for FPR1 Table I
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