[Laser] Ramsey laser communications kit

[John Schnurer]

	Dear Group,

	Some Brief notes:

	These notes are about solid state lasers in metal packages, the
"raw" laser, used for laser pointers and many other low power
applications:

	A)	The package OFTEN has 3 leads:

		1]	A "common"
		2]	The lead to the LASER (abbreviated LS) 
		3]	A lead to a photodetector (abbreviated PD)
				of some kind

	B)	The idea is the the PD is used to close a servo loop or
error correction around the LS to stabilize the operating parameters, ie
optical output of LS creates a signal in the PD ... and these electrical
connections are coveyed to an IC (integrated circuit) Designed to take the
signals and make all work together.... there are also discrete and mixed
circuits.

	C)	There is NO standardization of polarity of LS or PD
with respect to common.......

	D)	IF you have an operational device you can, in some
cases, emprically determine the relationships of PD:  Measure
current, if will not be much compared to LS, a BUNCH of current and all
measures should use at least:

	1]	common
	2]	the two battery or power supply leads
	2]	the unknown LS and PD

	E)	SOME laser pointers and so on have a 3 lead LS package and
while it DOES have a PD, the OD is not Used.


	If at all possible, find the manufacturer, and ask for pin out and
applications schematics.  One can often set up the suggested
manufacturer's circuit, often with one of their IC drivers and then simply
summ in of add a TINY signal to the PD pin or some location in
the correction circuit and so thereby simply modulate the laser.

								JH