Patent ID: 7944956

Claim:
A laser stack apparatus comprising a first heat sink, a second heat sink, a first semiconductor laser element, and a second semiconductor laser element, wherein each of the first heat sink and the second heat sink comprising: an electrically conductive first flat plate having an upper surface in which a first recess is formed; an electrically conductive second flat plate having a lower surface in which a second recess is formed, and an upper surface on which the heat generating body is to be mounted; an electrically conductive partition plate having a lower surface covering the first recess, an upper surface covering the second recess, and at least one through hole having the first recess communicated with the second recess; a refrigerant inlet extending from one of the first recess and the second recess and adapted for inflow of a refrigerant into the heat sink; and a refrigerant outlet extending from the other of the first recess and the second recess and adapted for outflow of the refrigerant from the heat sink, wherein the first flat plate and the second flat plate both have a first coefficient of thermal expansion, and wherein the partition plate has a second coefficient of thermal expansion lower than the first coefficient of thermal expansion, and wherein the first semiconductor laser element is located between the upper surface of the second flat plate of the first heat sink and a lower surface of the first flat plate of the second heat sink and has a coefficient of thermal expansion lower than the first coefficient of thermal expansion, wherein the second semiconductor laser element is mounted on the upper surface of the second flat plate of the second heat sink and has a coefficient of thermal expansion lower than the first coefficient of thermal expansion, wherein the first flat plate has a thermal conductivity higher than the partition plate, wherein the first flat plate and the second flat plate are comprised of Cu, and wherein the partition plate is comprised of one of Ni, Au, W, Pt, and stainless steel.