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Hi, I am sure galvonometer could be the problem. For a more detailed answer you have to provide a more detailed question. Singlemode

As far as I understand the OP wants to detect the doppler shift of a vibrating surface to reconstruct the audio spectrum. This shift can be detected by an unmodulated beam or a modulated one. Since the OP stated that his detector has a high dc level already from stray light, he needs to improve...

This will only work if your DAC has a higher bandwidth than your modulation frequency. There is a reason why radio and optical telecommunication use modulation techniques at high frequencies. This noise is at low frequencies and you could get rid of it by using a FM or AM scheme. If you...

Hi, this is an interesting project and I think there is space for improvement. First the general scheme: Measuring something at DC is in general a bad idea if the signal to noise ratio is bad. Moving to a high frequency by modulating your laser removes low frequency noise from your system. To...

This is pretty cool! The use of a fiber eliminates beam mismatch and allows for a true rgb laser beam. Singlemode

Moisture is a problem for shure, along with dirt. At least for GaN laser diodes oxygen seems to be needed for preventing a reaction of nitrogen and the facet. Singlemode

Great beam pics and a great laser too! Singlemode

The OP don't gave us more information about his project and not a lot other informations either. If lag is important (active feedback scheme o s.e.) than other laser types than dpss are a suitable choice. If not, every led will do the job, kHz modulation was perfected decades ago. Singlemode

Welcome and be safe. Singlemode

I modulate laser diodes with frequencies up to the GHz range without any problems. If your current driver doesn't have a wideband modulation port, use can use a simple bias-tee to couple your AC signal in. Singlemode

The main reason for the diode can is the protect the diode from water and dust particles that would stick on the diode facet and destroy the diode in the longterm. This is even worse for high power diodes because the beam creates an optical tweezer that pulls small particles to the point of the...

I think that only looking at the beam. div. specs without knowing if it is a single or multi mode diode is not useful at all. Because the raw divergence of the diode has no relation to the final divergence when collimated with a lens. Singlemode

These diodes seem to have good specs and I am looking to see some beam pics and measurements. Still waiting for the single mode 1W 450nm diodes that OSRAM is developing for the car industry! Singlemode

Sharps datasheets for the 485nm shows the pins from the top (their outlines are broken lines) and not looked from the pin side. So you have to flip them, but the pin numbers on the right are flipped too. Some how confusing.... Singlemode

Regardless of collimated or not, Watts of power hitting your eyeball are enough to boil the water inside them. While you want get this from diffuse reflections, metalic surfaces or mirrors are common in the typical household. Laser safety first! Singlemode

Exactly, the lenses in your eyes are designed to focus a collimated beam on a tiny spot at your retina (it appeared to be a huge evolutionary advantage for our ancestors to see things far away, like predators or something to eat) like a camera lens does. So even some mW can be dangerous if...

Looks awsome, You got your own rainbow here! Singlemode

Now your question is clear to me: Only when your fiber is perfectly straight. Any deviation from that will change the incident (and then the reflected angle) until the angle is redistributed over all possible angles and then leaves the fibre with an NA of 0.5 in your case. Like described...

Hi, your question makes no sense at all. The aperture of your multi mode fibre and its core diameter are two independent things and are listed with the fiber datasheet. How can we help you? Singlemode Ps: Please introduce yourself in the appropriate thread.

I could do a CAD drawing for you but not the actual machining. Singlemode