January 9, 2018

Five Sources of CW Laser Diode Failure and How to Prevent Them

Continuous Wave (CW) laser diode arrays are principal components of modern medical, automotive, and defense equipment. As such, the reliability and longevity of the instruments rest upon the reliability and longevity of the laser diode array. This article describes five common causes of failure and how to avoid them.

 

1. Storage and Assembly Environment

Laser diodes must only be handled in controlled environments. Heat, humidity, and contaminants can all damage laser diodes.

  • Store laser diodes in a clean, dry environment in the original packaging/container.
  • Never allow the packaging to exceed the minimum and maximum storage temperatures (generally -30°C to 70°C, unless specified otherwise).

It is recommended that laser diode components be kept inside an ISO Class 7 cleanroom environment until they are integrated into an appropriate system designed to maintain the same level of cleanliness. 

2. Electronics

Laser diodes are susceptible to damage from electrostatic discharge. They are most vulnerable in the interval between when they are unpacked and when they are secured within the system.

  • Use grounded wrist straps and grounded anti-static mats at all times when handling a laser diode.
  • Keep the leads electrically shorted until you are ready to connect the laser to the system wiring.

3. Optics

In addition to electrical concerns, the front facet of a laser diode is susceptible to damage from mishandling. Any contamination resulting from contact with the laser output facet may lead to irreversible damage and failure of the laser diode, even if there is no sudden failure.

  • Always wear powder-free latex or nitrile gloves when handling a laser diode.
  • Avoid exposure to dust, water, or other surface contaminants.
  • Never attempt to clean the front facet.
  • Do not solder near the front facet.
  • Do not store near volatile products such as glues, paints, or solvents, as these materials may deposit onto the front facet.

4. Electrical Driver

Laser diodes require precise control of operating current and voltage to avoid overdriving the laser. The correct driver will protect against power surges, transients, and fluctuations.

  • Ensure that the laser diode is correctly matched to the polarity of the driver. DO NOT operate the laser diode with reverse polarity.
  • Use electronics designed specifically for laser diodes.
  • Install a reverse protection diode close to the laser diode to protect against reverse current spikes.
  • Use appropriately sized electrical cables and connectors.
  • Ensure that the power supply does not produce any leakage current when in the “off” state.
  • Avoid current spikes during turn-on and turn-off.
  • Tune the drive circuitry to provide a critically damped response without any ringing or oscillations.

5. Coolant System

High power laser diodes generate large amounts of waste heat. Proper cooling is crucial to extending the life of the laser. For systems using fluid cooling, there are some essential precautions.

  • Ensure that the cooling fluid chemistry is compatible with the heatsink.
  • Maintain adequate cooling fluid flow rates.
  • Ensure that the cooling system has sufficient cooling capacity to maintain the recommended operating temperature range for long-term operation.
  • Avoid growth of microorganisms in the cooling water.
  • Provide appropriate filtration directly upstream of the laser diode.

Leonardo Electronics US diode lasers are notable for superior operation and reliability. Adhering to the above precautions and instructions will avert unintended damage and ensure that our lasers operate as warranted. If you ever have questions about proper laser diode handling or installation, don’t hesitate to contact us. Our engineers and technicians are always prepared to answer technical questions about our products. You can also download instruction manuals for our water-cooled laser diodes and our conductively cooled laser diode arrays. 

 

To learn more about using laser diodes and high energy laser systems for your emerging application, download our white paper.

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