Datasheet

CHAPTER 3. STARTER KIT (PULSER, TEMPERATURE CONTROLLER, ETC...) 14
the pulse current must always result in increased optical power output, otherwise
the DC bias current is already too high.
• As a rule of thumb, the overall dissipated power (sum of DC bias current dissi-
pation and pulse current dissipation) must never be higher than the average dis-
sipated power given by the highest current / voltage / temperature combination
specified in the datasheet. Take into account that the average dissipated power
for a given pulse current I, pulse voltage U, and duty cycle d is given by d × I × U,
whereas the dissipated power due to a bias current IB is given by IB × U. (U is
the voltage on the laser, but it is safe for this calculation of bias current dissipation
to use the voltage on the LDD pulser input.)
3.4.5 What are the current and voltage ranges of the bias-T circuit?
Since the input stage of the bias-T is a bipolar transistor, applied voltage must be
higher than about 0.6V to start bias current. The input stage has maximum voltage
limit of 2.6V, but the laser itself may be destroyed at lower bias-T control voltage al-
ready, therefore the maximum rating has to be checked with the abovementioned rules
and together with Alpes Lasers SA.
The monitor output (if available) allows measurement of applied DC bias current: Its
voltage divided by 10 Ω gives bias current. In general, bias current can be in the range
of 0.1A, but this must be checked with Alpes Lasers SA before.
Avoid reverse polarity on the input!
3.5 Laser Laboratory Housing (LLH)
3.5.1 What is the distance of the laser die output facet from the window external
facet?
This distance is approx. 4.5 mm.
3.5.2 What is the reflectivity of the LLH window?
For complete data and information about the LLH window, please refer to the website
of Janos (www.janostech.com) and see the characteristics of ZnSe3-12 IR coating.