Instructions for Handling Diode Lasers


Instructions for handling and employing diode lasers are provided below.
Red diodes are much more susceptible to damage than infrared diodes. Please look through these comments and think about how you are
employing the diodes to make sure you are doing everything possible to get a long lifetime from them.
We want you to have a success using these products.

     
   Keep the diodes clean. They should not be operated in an environment where dust particles in the air can reach the active region of the diode.
   Keep the diode stripe (which emits light) dry. if you store the unit in a high humidity, the optical coatings will be damaged and render the diode
     useless.
   Operating the laser at a temperature lower than recommended usually translates to slightly increased output power and an improved lifetime.
   Heat : This is the biggest cause of field failures. Many customers do not appreciate the importance and/or the complexity of removing waste
                 heat.
                 The importance and/or the complexity of removing waste heat. Because operating temperature has a strong influence on laser lifetime,
                 The heat-sinking of the laser package is of tremendous importance and doing it well is not as simple as many assume it is.
                 A high power laser  diode is roughly 1/3 efficient: a one watt laser will generate about 2 watts of heat. This waste heat must be removed
                 efficiently and instantaneously, or the laser will quickly heat up and burn out, or, as a minimum, experience an abbreviated lifetime.
                 The laser can be operated at higher temperatures than recommended, but the lifetime of the laser is reduced exponentially as the
                 operating temperature is increased. The laser package must be securely attached to a cooled heatsink. The heatsink may be cooled by
                 water, air, or thermoelectric coolers. The best heatsink material is copper, but aluminum is also a fair heat conductor.
                 If aluminum is used, the surface should not be anodized in the region where the laser package makes contact with the heatsink.
                 The aluminum oxide anodized coating makes an effective thermal insulator. The diode package should be attached to a heatsink plate
                 at least several millimeters thick. Thermal compound, or anindium foil washer can be used to reduce the thermal impedance of this
                 interface. Finally, when testing out a heatsink configuration, it is wise to test the temperature drop between the laser package and the
                 heatsink using a very small thermocouple touched against the base of the package. The temperature drop during laser operation should
                 be only 1-2 C.
   Laser diodes need to be driven by an approved power supply/driver or they may well be damaged/ruined rather quickly. Off-the-shelf drivers
     often deliver a high spike of current at turn-on, and they deliver a very short duration reverse biasing when the unit is turned off.
     Either of these will damage/ruin the diode laser.
   Laser diodes are very sensitive to damage by electrostatic charges, or other voltage transients. The laser should be handled using static-safe
     procedures when it is taken out of its static-protective shipping container. When the laser is not connected to a power supply, it is wise to
     short the anode and cathode together to prevent static damage. The laser should be driven from a current-regulated power supply which is
     designed specifically for laser diodes. The power supply should create no surges or spikes, and no reverse voltages and should not have any
     ringing.
     Many poorly designed power supplies have voltage transients during turn-on, turn-off, or in the case of power failure. Never make the
     connection to the laser diode with the power supply voltage on. Most laser diode power supplies have provision to disable the supply and short
     the output to allow for connection of the diode.
   Some laser diodes are susceptible to damage from back reflections into the device. This is more the case with lower wavelength material than
     with higher wavelengths. Thus, when attempting to collimate the output, care must be taken to avoid back reflections.
     Note that the threshold current increases and the slope efficiency decreases as the operating temperature is increased.
     The emission wavelength changes with temperature: the wavelength changes about +1 nm for every 6 C increase.
     This value varies a little from wafer to wafer.