Tunable single-mode coupled-cavity laser in a standard InP photonics platform

Area of Science:

• Photonics and Laser Technology
• Semiconductor Device Engineering

Background:

• Standard indium phosphide multiproject wafer (MPW) shuttles typically lack integrated distributed feedback (DFB) gratings, limiting single-mode laser fabrication.
• Achieving tunable, single-mode laser operation is crucial for applications in optical communications and spectroscopy.

Purpose of the Study:

• To demonstrate a wavelength-tunable, single-mode laser fabricated on an indium phosphide MPW without DFB gratings.
• To investigate the performance characteristics, including tunability, side-mode suppression, and optical linewidth, of the proposed laser design.

Main Methods:

• Fabrication of a coupled-cavity laser utilizing reflections from engineered slots within the laser cavity on a standard indium phosphide MPW.
• Characterization of the laser's wavelength tunability by adjusting applied currents to different laser sections.
• Measurement of side-mode suppression ratio (SMSR) and optical linewidth using delayed self-heterodyne spectroscopy.

Main Results:

• Successful implementation of single-mode operation enabled by cavity slot reflections, overcoming the absence of DFB gratings.
• Demonstrated wavelength tunability of 20 nm around 1560 nm by current modulation.
• Achieved a maximum side-mode suppression ratio of 46 dB.
• Observed a Voigt line shape in the delayed self-heterodyne spectrum, indicating optical linewidths of 3.7 MHz (Lorentzian) and 88 MHz (Gaussian).

Conclusions:

• The presented coupled-cavity laser design effectively achieves tunable, single-mode operation on standard indium phosphide MPWs.
• The use of cavity slots provides a viable alternative to DFB gratings for single-mode selection.
• The laser's performance metrics, including tunability and narrow linewidth, make it suitable for various photonic applications.