Optical Feedback Dynamics in Semiconductor Lasers
Summary
Semiconductor lasers exhibit a rich array of dynamical behaviours when subject to optical feedback. Reflected light from an external cavity re-enters the gain region, altering carrier and photon populations. Depending on feedback strength, phase and delay, the system may settle into stable continuous-wave emission, self-pulsations, square-wave oscillations or coherence collapse characterised by broadband noise and irregular intensity fluctuations. The underlying mechanisms are well described by delay-differential rate equations, often based on the Lang–Kobayashi formalism, which predict multiple external cavity modes and bifurcation scenarios including Hopf instabilities and saddle-node collisions. Practical implications range from coherence degradation in optical communications and coherence tomography to deliberate exploitation of feedback for sensing, distance measurement and neuromorphic photonic computing. Advances in photonic integration have further enabled on-chip control of feedback parameters through passive and active elements, enhancing laser stability, directionality and single-frequency operation in complex photonic circuits.
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Optical Feedback Dynamics in Semiconductor Lasers publication trend
The graph below shows the total number of articles in optical feedback dynamics in semiconductor lasers across all publications each year (not limited to Nature Index journals).
Technical terms
Optical feedback: Light reflected back into a laser cavity from external components, influencing its dynamics.
External cavity mode: A resonant state formed by the interplay of the laser cavity and an external feedback path.
Lang–Kobayashi model: A set of delay-differential rate equations describing carrier and photon dynamics in a laser under feedback.
Coherence collapse: A regime of irregular, broadband output induced by strong feedback disrupting stable lasing.
Bistability: The coexistence of two distinct stable lasing states under identical operating conditions.
Ring laser: A laser architecture in which light circulates in a closed loop, often used to study directional mode competition.
References
- Distance measurement by delayed optical feedback in a ring laser. Optical and Quantum Electronics (2022).
- Directional power distribution and mode selection in micro ring lasers by controlling the phase and strength of filtered optical feedback.. Optics Express (2018).
- Semiconductor racetrack resonator coupled to an S‐bent waveguide: Influence of the coupling coefficients on the unidirectional operation. IET Optoelectronics (2021).
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