Datasheet

Chapter 5: Starter Kit Operation

5.2.3. Maximum duty cycle

The TPG is capable of operating with pulses as long as 200 ns; however for short

periods (high duty cycle) the following limitations apply:

T=400ns: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . t max = 200ns

T=300ns: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . t max = 200ns

T=250ns: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . t max = 150ns

T=200ns: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . t max = 100ns

where T is the period and t

max

is maximum pulse length.

CAUTION:

The laser shall only be operated under conditions as speciﬁed in

the datasheet or by ALPES LASERS directly: all other operation may

result in the destruction of the laser and loss of warranty.

While the TPG alone is capable of exceeding a duty cycle of 50% in some con-

ditions, the maximum duty cycle of the pulser system is of 50%; a fuse protects the

TPG from operating at larger cycles when under load. If larger cycles are needed,

the LDD must be powered by an external 12V power supply. To operate a laser with a

duty cycle higher than speciﬁed, it is mandatory to monitor its average output power

and comply to the following guidelines:

• do not increase the duty cycle further when the power saturates, but rather

reduce it.

• it is advisable to increase the duty cycle by reducing the pulse period, rather

than increasing the pulse length, since the latter is more likely to damage the

laser: increasing the pulse length increases the short time heat load on the

laser, as reducing the pulse period increases the average heat load.

• the exact percentage of maximum duty cycle depends on the laser

64 QCL user’s manual v3.0