Can I Use the Pickup from a CD Player or CDROM Drive for Interferometry?
), the comments below are the first I have seen to suggest that performance using some common laser diodes may be at least on par with that of a system based on a typical HeNe laser (though not a high quality and expensive frequency stabilized single mode HeNe laser). While I don’t know how to select a laser diode to guarantee an adequate coherence length, it certainly must be a single spatial (transverse) mode type which is usually the case for lower power diodes but those above 50 to 100 mW are generally multimode. So, forget about trying to using a 1 W laser diode of any wavelength for interferometry or holography. However, single spatial mode doesn’t guarantee that the diode operates with a single longitudinal mode or has the needed stability for these applications. And, any particular diode may operate with the desired mode structure only over a range of current/output power and/or when maintained within a particular temperature range. (From: Steve Rogers (scrogers@pacbell.net).)
