Fast Frequency Shift of Laser Diode by Optical Short Pulse Irradiation
It is possible to modulate frequency of a laser diode (LD) applying an irradiation on its active layer.1 There have been considered several causes for the modulation phenomena. We have already confirmed optical modulation of a LD up to 200 kHz applying sinusoidal power modulated optical beam on the active layer of the LD.2,3 The frequency modulation depth depends on the power of the irradiated optical pulse although it is quite small (- 4.3 × 10-4/ W). The reason of the modulation is reduced to the photo-thermal effect. The upper bound of the modulation frequency is expected, however, higher than 200 kHz due to certain causes other than the photo-thermal effect. In order to explore the upper bound, we carry out an experiment to modulate frequency of a LD, whose wavelength is 780 nm, by irradiating its active layer with a very short laser pulse. Oscillation frequency of the LD may shift due to the fast change of refractive index of the laser material.
KeywordsLaser Diode Active Layer Autocorrelation Function Optical Pulse Spectrum Analyzer
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