Method for preparing borate-based crystal and laser oscillation apparatus

A method for producing a borate-based crystal, which comprises:

• employing a water-soluble cesium compound and a water-soluble boron compound as starting materials,
• dissolving all of the starting materials simultaneously in an amount of water which is 1.0 to 2.5 times the total weight of the starting materials,
• forming an aqueous solution with a uniform composition,
• evaporating the water in the aqueous solution, followed or not followed by sintering, to form a crystal growth material,
• melting the crystal growth material, and
• growing a cesium-borate-based crystal of the composition formula:
• Cs1-xMxB3O5 (0≦x<1)
• wherein M is an alkaline metal or alkaline earth metal element,
• wherein the water-soluble cesium compound is a cesium carbonate compound, and
• wherein a decarboxylation reaction occurs in the aqueous solution by dissolving the starting materials in water.