Research On Reducing Coherence Of Laser Diode

The light source which is high beam quality, low coherence, high brightness is useful for biological medical imaging, optical fiber sensing measurement and other fields. This paper puts forward the method of reducing laser diode’s temporal coherence length by radio frequency modulation, so the low coherence laser diode is widely used in these fields.We change radio frequency modulation frequency and modulation depth in order to find out the best radio frequency modulation parameters where laser diode’s temporal coherence length is lowest. And based on this, we design depolarizer for the low temporal coherence laser diode and set up the system to verify the performance of depolarization.By this method, laser diode’s temporal coherence length is reduced to130um, which is38mm without radio frequency modulation.what’s more, Degree of polarization (DoP) is reduced to0.85%by the depolarizer which we design according to the low temporal coherence.