Alpes Lasers . TC-3 Datasheet download pdf (Page 121)

B.3 Bias-T circuit for pulsed lasers

Procedure

1. set the temperature to 15

C so that any moisture inside the package does not

condense on the laser chip

2. Use current settings as indicated in the ALPES LASERS datasheet

3. start the laser: the powermeter (if installed) should indicate some power dissi-

pation

4. set the temperature to allow the highest frequency (shortest wavelength) of in-

terest to be emitted

5. Reset the current to settings appropriate for that temperature and wavelength,

then reduce it a little bit further - but not below threshold (so you still see energy

on the detector)

6. put a gas cell between laser and detector and verify that you can still see the

laser energy on the detector; take note of the amplitude of the detector signal.

7. Turn on the bias T current to a low value (typically 0.001A) and record the de-

tector signal

8. repeat at 0.001A increments of bias-T current recording values for each incre-

ment until 0.060 A is reached (or some other value that has been discussed/agreed

with ALPES LASERS) If the temperature and pulse current starting points were

right, the line of interest should be visible in the data when plotted. If not, per-

form the same procedure with new temperature and pulse current settings.

9. Continue to optimize the temperature and drive parameters

a) Adjust the pulse length lower and higher and repeat the scan; thus learn

about the effect of these parameters on power and laser linewidth

b) If possible, repeat the measurement with a gas cell with the target gas at

low pressure (1 Torr). This will narrow the line greatly and allow to consider

the apparent spectral resolution of the laser itself under the drive conditions

and to learn whether the driver has any ringing or double pulsing (which

will make the line width seem higher).

2014 SA 111

1 2 ... 116 117 118 119 120 121 122 123 124 125 126

No comments

Alpes Lasers . TC-3 Datasheet Page 121