Distributed feedback lasers using surface gratings in Bragg waveguides.

Area of Science:

• Semiconductor lasers
• Photonics
• Integrated optics

Background:

• Narrow-linewidth lasers are crucial for applications like spectroscopy and optical communications.
• Existing semiconductor laser technologies face challenges in achieving both narrow linewidths and stable single-mode operation.

Purpose of the Study:

• To report the first narrow-linewidth edge-emitting semiconductor distributed feedback Bragg reflection waveguide diode laser (DFB²RL) operating around 790-800 nm.
• To characterize the performance of these novel DFB²RL devices.

Main Methods:

• Fabrication of DFB²RLs using a ridge waveguide structure.
• Incorporation of a 5th order, surface-etched grating as the wavelength-selective element.
• Testing of unbonded devices with a 500 µm cavity length.

Main Results:

• Continuous wave threshold currents around 25 mA.
• Output power of 2.5 mW per facet at 100 mA drive current.
• Single longitudinal mode operation with side-mode suppression ratio (SMSR) up to 49 dB and linewidths as low as 207 kHz.
• Stable single-mode operation maintained over a 9 nm wavelength range with temperature variations from 15°C to 50°C.

Conclusions:

• The developed DFB²RL is the first of its kind in the 790-800 nm range, demonstrating excellent performance.
• The device exhibits high SMSR and narrow linewidths, suitable for demanding applications.
• The laser shows robust single-mode stability across a practical temperature range.