Articles written in Pramana – Journal of Physics

    • Modelling and characterisation of the noise characteristics of the vertical cavity surface-emitting lasers subject to slow light feedback


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      This paper introduces the modelling and characterisation of the noise properties of the vertical cavity surface-emitting laser (VCSEL) coupled in lateral direction with a passive cavity. This design of VCSEL with this transverse coupled cavity (TCC) is proposed for high-speed photonics. We introduce comprehensive simulationson the influence of the induced lateral slow light feedback on the relative intensity noise (RIN) and carrier-to-noise ratio (CNR). The proposed model incorporates multiple round trips of slow light in the TCC as time delay light in the rate equations of the VCSEL. The obtained results are compared with those of the conventional VCSEL.We show that the noise performance of the TCC-VCSEL is optimised when the VCSEL exhibits stable continuous wave (CW) operation under strong slow light feedback and the TCC length is smaller than 8 $\mu$m and between 11 and 13 $\mu$m. When strong slow light induces unstable regular and/or irregular oscillations, RIN is enhanced and CNR is lowered.

    • Modelling of semiconductor laser with double external cavities for use in ultrahigh speed photonics


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      We model and investigate the dynamics and modulation performance of semiconductor laser integrated with two short external cavities facing the front and back facets with the aim to enhance the modulation bandwidth of the laser for use in high-speed photonics. The coupled cavities provide double optical feedback (DOFB) to the laser cavity through the partially reflecting facets of the laser cavity. The study is based on modifying the rate equations of the laser to include multiple reflections of laser radiations in the external cavities. Therefore, it accounts for the regime of strong OFB that causes bandwidth enhancement. We introduce correspondence between the laser stability under DOFB and the modulation response characteristics. Also, we allocate the ranges of the DOFB that induce photon–photon resonance (PPR) effect as the main contributor to the bandwidth enhancement. We show that the intensity modulation (IM) response can be tailored by varying the reflectivity of the external mirrors when the external cavities are too short to stabilise the laser output. Modulation bandwidth better than 55 GHz is predicted under strong double OFB when the external cavities are as short as 2 mm. Stronger DOFB is found to enhance the PPR effect and induce resonant modulation over a narrow frequency range around frequencies reaching 45 GHz.

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