Optical module using a capacitor to suppress warpage

An optical module, comprising:

• a base having a predetermined product of a coefficient of linear expansion and a Young's modulus, wherein the base includes a substrate made of ceramics and having a side with a certain size;
• a planar lightwave circuit element including silicon or silica-based glass as a constituent material and having a first side with a first size and a second side opposite to the first side and with a second size same as the certain size of the substrate, the planar lightwave circuit element being mounted on the base by an entire surface of the second side being joined with the side having the certain size of the substrate in the base;
• and
• a warpage suppression component having a third size smaller than the first size, including a metal element as a constituent material, being mounted on a surface of the first side of the planar lightwave circuit element so as not to overlap with a waveguide included in the planar lightwave circuit element, and having a product of a coefficient of linear expansion and a Young's modulus that reduces warpage of the planar lightwave circuit element in accordance with warpage of the base depending on temperature change, wherein the product of the coefficient of linear expansion and the Young's modulus of the warpage suppression component is 0.6 times or more, and 1.5 times or less, than the predetermined product of the coefficient of linear expansion and Young's modulus of the base, wherein the warpage suppression component is a capacitor, and the optical module is configured as an optical modulator.