Optical coupling of two diode lasers

Abstract

Two laser diodes of about equal length have been coupled by conventional optics. Threshold reduction of the coupled system compared to the thresholds of the isolated diodes have been observed. From these measurements the coupling coefficient has been calculated. The cooperative behaviour of the coupled diodes is confirmed by an increase in light intensities and a decrease of the halfwidth of the light pulses observed on both diodes if they are simultaneously excited. The spectral measurements have shown that in the coupled mode both diodes emit the same spectrum.Zwei Laserdioden wurden gekoppelt, indem mittels konventioneller Optik die beiden aktiven Zonen aufeinander abgebildet wurden. Der Kopplungskoeffizient des Systems wurde abgeschiitzt aus der bei simultaner Anregung der gekoppelten Dioden aufgetretenen Schwellstromerniedrigung. Neben der Erniedrigung der Schwelle wurde in beiden Dioden eine Zunahme der ausgekoppelten Lichtleistung sowie eine Abnahme der Halbwertsbreite der Lichtpulse beobachtet. Spektrale Messungen zeigten, daB die Emission der beiden gekoppelten Dioden identisch ist.

Rate equation approach for diode lasers

“…Experiments on Q-switching [1,2] and self modulation [3,4] as well as on mode selection [5,6] and on mode synchronization [7][8][9] have confirmed these properties. Compound systems are of interest because they can be used to influence the dynamic and spectral behaviour of the laser emission.…”

“…Since the two coupled diodes were selected to have about the same properties (length, spectrum) [8], no quenching effects or bistable operation could be observed. It is seen from these equations that the photon numbers in both diodes increase with increasing coupling coefficient at any pumping level.…”