Abstract

The anticorrelation or competition dynamics of two-mode semiconductor lasers has formed as an attractive field of both experimental and theoretical interest [1]. Quantum dot (QD) lasers emitting on ground-state (GS) and excited state (ES) have shown to exhibit temporal GS and ES output power fluctuations [2]. Recently, coupled two-state QD laser emission was reported where the carrier coupling between GS and ES could be identified as its origin [3]. In this work, we comprehensively study the spectrally-resolved amplitude stability of an InAs/InGaAs QD laser emitting at GS and ES wavelengths of 1250 nm and 1180 nm in dependence on laser biasing conditions. The investigated laser has a cavity length of 2 mm, is temperature stabilized at 14 °C and the emission facet is as cleaved. The experimental setup is depicted in the inset of Fig. 2. The laser is driven by a low-noise current source, the emitted light is collimated, passed through an optical isolator (60 dB isolation) and is then spectrally and spatially separated by a diffraction grating. The two GS and ES beams are then filtered by a slit and focused onto the direct-detection setup (dashed box, inset of Fig. 2). Amplitude stability is quantified by measuring the relative intensity noise (RIN). The measured spectrally-resolved output power is depicted in Fig. 1. The colored dashed lines in Fig. 1 and 2 should serve as a guide to the eye for the GS, ES thresholds and an equal-power-point. The laser starts emitting on GS and above 162 mA, simultaneous GS and ES emission evolves. At an injection current of 247 mA an equal power point is reached. The RIN measured at 25–30 MHz is shown in Fig. 2.

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