Combined laser diode/thermoelectic cooler controller selection guide

This page is a selection guide for applications that require both laser diode drive current and precise temperature regulation through a thermoelectric — or Peltier effect — cooler (TEC).

Our product line offers two general approaches. In the integrated approach a single unit provides both laser drive and the TEC control. In the combined approach the TEC controller and the laser diode controller are separate units. They can be interfaced individually or as a single functional unit using our TEC controller's “passthrough” feature. Any combination of TEC controller and single-channel laser diode controller can be used in this way.

When the integrated approach is available it is generally preferable. In order to evaluate this possibility you must consider the following parameters:

• The maximum intended operating current for the laser diode, keeping in mind possible degradation due to aging of the laser.
• The maximum voltage drop expected for the laser diode, which is the sum of the diode operating voltage and the ohmic loss in the cables and connectors.
• The maximum voltage of your TEC.

In most cases there is a range of TECs that will meet the cooling requirements of your system. Selecting one that matches the capability of one of standard drivers will significantly simplify the control task.

When no integrated solution is available, the laser diode driver and the TEC driver can be chosen separately based on their separate characteristics. See the TEC controller selection guide and the single-channel laser diode controller selection guide for more information.

Our laser diode controllers are current sources. You command a specific current, and the voltage that results is a characteristic of the load (the diode plus cables and connectors) rather than the driver. The driver shuts off to protect itself when the output voltage drawn exceeds its capabilities. The limit at which this occurs is termed the compliance voltage.

Each product line is optimized for a different range of applications. The three products in our DPSS line drive a single laser diode and two TECs. The HCT is for a higher current diode and one TEC.

The HCT is designed for high current loads and therefore becomes excessively noisy at low current. For this reason it specifies a minimum current of 5A [check this!], and its firmware will prevent the laser diode driver from turning on below this point. If your requirements include operation under these conditions please contact us.

Our TEC drive units incorporate advanced control logic that will servo the temperature to a user-defined set point. The driver controls the voltage applied to the TEC, and the current that results is a characteristic of the TEC rather than the driver. In the event that the TEC tries to draw more current than the driver can provide, a shutoff will occur to protect the driver. When this occurs the laser will be automatically shut off as well.