3. Operating Procedure

High power laser diodes require proper heat dissipation to maintain the chip temperature within rated levels and assure a long lifetime. The optical conversion efficiency of a laser diode is approximately 30%, and most of the DC power is dissipated from the package as heat, so absolutely avoid operating a laser diode without a heat sink. Also, the package and the laser diode may be electrically connected, so care should also be taken for the circuit.
Sony's medium and high power laser diodes are currently mounted in the φ9 mm V package and the special square shape XT and YT packages. These packages have the following approximate thermal resistance from the chip's laser resonator area to the package's external surface. This value is measured by the standard ΔVF method.
V package: 42ºC/W (including the laser chip's thermal resistance)
The standard method for mounting the SLD300 series laser diode to the heat sink of the V package is shown below. Using silicon grease or other material between the package and the heat sink is recommended to increase the thermal contact. However, take care not to allow the silicon grease to adhere to the glass surface.

Since most of the heat dissipated from the laser chip is drained from the underside of the package, make sure that the heat sink makes good contact with the bottom flange of the package. The characteristic values of a laser diode are specified in terms of the case temperature Tc (thermistor reading temperature for packages with a built-in TE cooler, cooling water temperature for water-cooled package). For example, when the SLD323V is operated to provide an optical power output Po = 1W, approximately 2W of heat is generated.
This operating temperature is Tc = -10 to +30ºC, so attach an appropriate heat sink to provide for forced air or water cooling or cooling with a Peltier element, etc.
In the next section, the procedure for heat sinking with an external TE cooler and heat sinking for on-chip TE cooler packages shall be presented.