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Tristability of a semiconductor laser due to time-delayed optical feedback
A Loose1, B K Goswami, H-J Wünsche
1AG Photonik, Humboldt-Universität zu Berlin, Newtonstrasse 15, 12485 Berlin, Germany.
Summary
Researchers studied multistability in single-mode lasers with integrated feedback. They discovered tristability of continuous-wave states, relevant for optical communication and ternary logic applications.
Area of Science:
- Optics and Photonics
- Semiconductor Lasers
- Nonlinear Dynamics
Background:
- Multistability in lasers is crucial for advanced optical signal processing.
- Integrated photonic devices offer compact solutions for complex functionalities.
- Understanding laser dynamics under feedback is key to controlling output states.
Purpose of the Study:
- To experimentally and theoretically investigate multistability in a single-mode laser with integrated feedback.
- To explore the regime of tristability of continuous-wave (CW) states.
- To assess the potential of such devices for ternary logic applications.
Main Methods:
- Experimental characterization of a single-mode laser with integrated phase tuning and amplifier sections.
- Theoretical modeling using the Lang-Kobayashi equations.
- Analysis of multistability as a function of amplifier and phase currents.
Main Results:
- Observed tristability of CW states for specific ranges of amplifier and phase currents.
- Wavelength separation of tristable states matches dense wavelength multiplexing (DWDM) channel spacing in the C-band.
- Derived an analytic formula relating the maximum number of coexisting CW states to the linewidth-enhancement factor (α).
Conclusions:
- The studied single-mode laser exhibits tristability, a phenomenon tunable via integrated feedback.
- The device's characteristics are promising for ternary logic and DWDM applications.
- The linewidth-enhancement factor (α) is a critical parameter determining the number of coexisting stable CW states, with values between 5 and 8 found to support tristability.
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