Like the C-mount, the CoS (chip on submount) has the laser exposed without protection to the chip or its bond wires. User should be knowledgeable in the handling and mounting of this type package. The CoS is also highly desired when other optical components need to be in very close proximity to the front facet. The AlN submout is an excellent conductor of heat but the CoS will require cooling. Cooling should be accomplished with a thermal electric cooler (TEC) for best control of heat and provide the means for accurate frequency control.
The beam characteristics are similar to the TO-8 and the TOSA package with exception to the window interface.
The CoS has gold bonding pads for connection to a hybirid assembly or internal package connections. Use only Au wire bonds. Do not solder to the submount pads.