Side bands on diode laser (unexpected wavlength shift.)

Is the diode self-tuned or does it depend on the external F-P resonator for tuning?

Did the wavelength shift up or down, and did it shift smoothly or are you looking at mode hopping? If it's internally tuned I'd expect heating to lengthen the diode's resonator so that you can hop from fa to fb then back to fa as the resonator length changes by increments of a half-wavelength.

If it's externally stabilized the front face of the diode's internal resonator may be forming another resonator with the F-P's input side which changes length as the diode expands with heating.

Can you monitor the diode's temperature change with wavelength change to any precision?

(caveat- I'm still on my first cup of coffee)

Mark L. Fergerson

Well self tuned I guess. It's got an external grating that does feedback into the diode

Smooth... (Hmm up or down, I forgot.) So I had to increase the DC current to get back to the original wavelength.. Increasing the (DC) current is much the same as increasing the temperature. Both tend to make the diode go to shorter wavlengths.

Well not to *any* precision :^) But I've got 'typical' graphs of how the wavelength changes with temperature.

At 3:00 PM? An all-nighter?

I've not done a lot of measurements with RF injected currents. Next time I look at this I'll see what happens for lower frequencies. (Say

George H.

At a guess, the RF is confusing the DC bias supply.

Cheers

Phil Hobbs

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Hmm, That's an interesting idea. So the RF goes in via an sma right on the laser head, and the 'DC' current drive is in a separate box, connected by a 6 foot computer cable with DB9 connectors on the ends. The current drive is mostly copied from Jan Hall, RSI '93. There's a big inductor before the real DC part. But there's this opamp ~1MHz current modulation circuit that's on the laser side of the inductor. I've no idea how that behaves with 100 MHz leaking in from the back end.

Oh! I've also got these ESD protection diodes across the laser diode in the laser head. One Schottky in reverse, and three pn's in series in the forward direction.... (?)

Thanks, I've got a few things to look at.

George H.

George H.