Next to the wavelength and electro-optical specifications, reliability is one of the most important aspects to consider when selecting the “right” pulsed laser diode (PLD).
Achieve Excellent Overdrive Performance without Inflicting Damage
The life expectancy of a PLD depends largely on operating conditions. PLDs operated at short pulses of several nanoseconds or small repetition rates can be significantly overdriven without inflicting damage.
The application determines the lifetime and performance required of the laser diode. A suitable PLD and drive electronics can be selected based on these requirements.
Applications and their Requirements
While in some military applications, such as the optical ignition of thyristors, a lifetime of only a few seconds is sufficient, industrial security scanners require 24-hour operation that can be guaranteed over the course of several years.
Empirical Evaluation of the Failure Rate
The following formula is used to determine the average failure rate of a 905 nm PLD; it is based on many years of experience and measurements:
MTTF = k * { P/L } -6 * t W -2 * F -1 * f ( T )
| k | constant | depends on laser material (e.g. 1,14 x 1020) |
| P/L | [mW/µm] | maximum optical power/length of emitter |
| tW | [ns] | pulse length |
| F | [kHz] | repetition rate |
| f ( T ) | = 1 @ 25°C | multiplication factor depending on housing temperature |
Life Test Rack for Application Simulation
To simulate the conditions of different applications, LASER COMPONENTS Canada constructed a “life test rack.” With this rack, fifty pulsed laser diodes can be tested at different parameters simultaneously. The following adjustments may be made: a pulse length of 100-500 ns, an operating frequency between 800 Hz and 25 kHz, and a temperature range up to +85°C.
Using this test rack, the optimal PLD can be selected to meet a customer’s individual needs.
Under given driver conditions the expected lifespan of various PLD models can also be determined. Testing whether a less expensive version is sufficient to meet the customer’s needs can save money later on in series production.
