Hybrid integrated narrow linewidth laser based on high-order SiO₂ planar waveguide grating.

Area of Science:

• Photonics and Optical Engineering
• Materials Science

Background:

• External cavity diode lasers are crucial for applications requiring narrow linewidth and high power.
• Traditional designs often face a trade-off between output power and spectral linewidth.
• Integrated photonic platforms offer miniaturization and scalability for laser devices.

Purpose of the Study:

• To propose and demonstrate a hybrid integrated external cavity laser.
• To achieve high output power and narrow linewidth simultaneously.
• To resolve the conventional linewidth-power trade-off in laser design.

Main Methods:

• Integration of a reflective semiconductor optical amplifier (ROA) chip.
• Utilizing a high-order silicon dioxide (SiO2)-based planar waveguide grating (SPWG).
• Fabrication on a low-loss commercial SiO2 platform.

Main Results:

• Demonstrated a single longitudinal mode laser.
• Achieved 55 mW output power at 300 mA pump current.
• Measured a Lorentzian linewidth of 614 Hz.
• Recorded relative intensity noise (RIN) of -165 dBc/Hz from 100 MHz to 250 MHz.

Conclusions:

• The hybrid laser design overcomes the traditional linewidth-power trade-off.
• The use of a simple high-order SPWG structure on a SiO2 platform enables high-performance lasers.
• This approach is suitable for mass production, offering a practical solution for advanced laser applications.