We have Diode tunable laser for 780nm. Recently, laser wavelength is not changing with temperature or current or the wavelength adjustment screw. Anyone has encountered similar problem?
The first assumption is that the diode "burned out".
With more information about the laser diode, or its characteristics, as well as a measuring instrument, I could answer more accurately.
Pavel Petrov But, laser is giving sufficient power and it has remained the same from past one year. Power has not degraded and lasing is happening.
Dixith Manchaiah The modes of a semiconductor laser depend on the physical dimensions of the emitting crystal. Therefore, a change in the temperature (expansion/contraction) of the crystal or the current flowing leads to a tuning of the laser wavelength. Perhaps an automatic wavelength stabilization system compensates for this tuning with a Bragg grating, for example?..
How do you control the wavelength of your laser? Do you have a wavelength meter of sufficient resolution?
Pavel Petrov We have wavelength meter highfinesse ws6. Previously, we had three ways for attaining required wavelength. LD current, LD temp control and wavelength adjustment screw in the laser. Now, adjustment screw is not providing any changes, with current and temp control some changes are happening but not in the required way.
During my research work at ITMO with Toptica DL100 ECDL, I encountered a failure of the piezo drive of the diffraction grating. The problem was solved by replacing it. Try to check the function of the piezo actuator.
Please satisfy my curiosity. I didn't have a wavelength meter like the WS6, I was tuning lasers by absorption in the spectroscopic cell. So I have no experience with a wavelength meter. The WS6-200, for example, has the best resolution of 200 MHz. At the same time, the ECDL Toptica line width allows the resolution of an hyperfine 5P Rb85 level structure. That is, the laser line width is on the order of units of MHz. Does WS6 allow you to see such a narrow line, or only roughly adjust the laser by hitting the Doppler broadening of the Rb vapor in the reference cell?
With current and temperature you can only change few tens of GHz, which may not be visible change in the wavemeter. You can see the change in the SAS spectrum more clearly when you change current or temperature. As you are saying you do not see any changes in wavelength with adjustment screw, I suspect that the optical feedback is not working properly. The wavelength change with adjustment screw should be over 15 nm.