Thermal Path and Duty Cycle for 1535 nm DPSS Sources

These things are small, and that's the problem. A 10 mJ pulse at 5 Hz is 50 mW of light. The pump behind it draws a good deal more, and the difference has to leave through a mounting face you could cover with a coin.

Energy times rate

10 mJ at 5 Hz and 100 µJ at 10 Hz are fifty times apart in average power. Same family, same wavelength, nothing in common thermally. That's why the millijoule models are held to 1–5 Hz.

The temperature range assumes a heat path

−40 to +65 °C is a baseplate figure. It assumes heat leaves through the mounting surface. A unit sitting in 65 °C air with a 90 °C baseplate is outside its rating, whatever the ambient says.

The interface, not the bracket

Flat surface, thin and even compound. Put a bracket between the source and the structure and you've added two interfaces and a resistance nobody costed. Bolting a small package to a rough plate leaves most of its area in air.

Bursts are fine. Sustained over-rate isn't.

A package this size has a thermal time constant of seconds. A few seconds at a higher rate works if you count the recovery. Running it there continuously doesn't, because the energy has to go somewhere eventually.

Measure the baseplate

Not the air. Twenty to thirty minutes to steady state, not two. Take energy and temperature at the same time, so a stable temperature with falling output points you elsewhere.

Four things worth recognising: output dropping after warm-up, shot-to-shot scatter at high duty, life short of the datasheet, condensation on the optics after a cold start.

If the baseplate sits 15 °C above ambient at steady state, look at the mount before you blame the laser.

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