vP high

Starter Kit Instruction Manual

Description

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4.6QCL pulse switching measuring unit

4.6.1Generalities

The measuring circuit contained in the LDD100 provides information about various laser pulse pa- rameters (peak voltages, supply voltages, duty cy- cle, frequency). They are only estimated values, since exact measurement of short and strong pulses with diodes and averaging circuitry is difficult.

Keep in mind that you should always measure the voltages on the LLH100 if you need accurate time and voltage data (see final paragraph). How- ever, these data are useful for monitoring and surveil- lance purposes, and to give a rough estimation of the current parameters.

4.6.2Measured voltages

UHV: 1/2 of the average voltage, respective to VHT (user supplied high voltage)

ULH: 1/2 of the average laser anode voltage, respective to VHT

ULL: duty cycle dependent peak laser cathode voltage, respective to VHT

UD: duty cycle dependent peak transistor drain voltage, respective to VHT

UPI: 1/2 average internally reshaped drive volt- age, respective to ground

UPT: 1/2 average of a 37ns fixed length pulse, respective to ground

4.6.3Timing data

Pulse frequency calculation

UPT can be used to calculate the pulse frequency as follows:

f= f 2U P T −νP low

0 νP high −νP low

Where f0 is a frequency constant, vP low and are the TTL pulser voltage limits.

Actual values: f0 = 371 ns , vP low =0.01V, vP high =5V

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Quantum Instruments Cascade Laser Starter Kit manual QCL pulse switching measuring unit, Generalities, Measured voltages