Re: Q: average power measurement with photodiode

Thank you for your feedback.

I have been thinking about power and energy meter. It looks complicate.

There are two well-known detectors to measure power and/or energy of
output from laser. The one is semiconductor-based and the other is
called thermal detector based on pyroelectric material.

What I am wondering is if there is any fundamental limit of each
detector to measure average power or/and energy per pulse of pulsed
laser (fs to us pulse duration, single shot to high repetition rate).

It seems that semiconductor head could measure average power down to
~100Hz. But it cannot measure single shot energy per pulse. Some
thermal detectors can measure the average power of high rep rate pulse
train. But cannot measure single shot energy per pulse. Some thermal
detectors can measure single shot energy per pulse but rep rate is
limited to tens of kHz not MHz. Wondering if there is any fundamental
limit or electrical circuit limit? I will appreciate if someone can
recommend any reference on this matter.

Thank you for reading.


Sam Goldwasser wrote:
"KK" <gcsel@xxxxxxxxx> writes:

Following up my question, it seems that photodiode can measure the
average power at low rep. rate based on Ophir website. In that case, I
am just wondering if the photodiode needs a special circuitary board.

The photodiode will have a maximum or "saturation" current beyond which
the output is not linear. If your laser's peak power is results in
something higher than this, it won't be accurate.

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KK wrote:
Currently I am having a difficulty to get a consistent result from
average power measurement. I have pulsed laser source running at 20kHz
to 500kHz. Pulse duration is ~ns.

I tried to use a cheap photodiode and the reading is converted into
power. It seems that power readings at low and high rep rates are
different.

I am just wondering if there is any limit to measure the average power
at low rep rate with typical photodiode.

Thank for looking.

.

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