Abstract
Langevin noise leads to inhibition of the temporal synchronization of the pulse oscillations from a gain-switched multimode semiconductor laser, resulting in the power reduction in optical beat detection. In this paper, the degree of the temporal synchronization of the pulse oscillations was examined by numerically estimating the output energy in THz time-domain spectroscopy (THz-TDS) using multimode semiconductor laser rate equations that include Langevin noise. The degree was estimated to be 95.5% from the ratio of the averaged THz-TDS output energy for the case where Langevin noise was included to that for when Langevin noise was excluded. Therefore, a gain-switched multimode semiconductor laser can be regarded as equivalent to optical pulses oscillating simultaneously in all modes in actual applications including optical beat detection.
Highlights
Gain-switched semiconductor lasers have been used as compact picosecond optical sources in many applications, such as distance measurements [1,2,3], nonlinear microscope imaging [4,5], and optical communications [6,7]
We have reported that the suppression of the timing jitter in gain-switched FP lasers is caused by a decrease in the coherence time of the amplified spontaneous emission (ASE) based on the broad bandwidth of multimode oscillation
Estimating the degree of temporal synchronization of the pulse oscillations from a gain-switched multimode semiconductor laser is an interesting subject of study
Summary
Gain-switched semiconductor lasers have been used as compact picosecond optical sources in many applications, such as distance measurements [1,2,3], nonlinear microscope imaging [4,5], and optical communications [6,7]. Estimating the degree of temporal synchronization of the pulse oscillations from a gain-switched multimode semiconductor laser is an interesting subject of study. A typical example is THz time-domain spectroscopy (THz-TDS) with a multimode laser as an input light source [16,17,18,19]. In this case, the THz-TDS output strongly depends on the degree of temporal synchronization of the light components among the multiple modes. Materials 2017, 10, 950 synchronization of the pulse oscillations from a gain-switched multimode semiconductor laser by simulating the THz-TDS output
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