1.3 μm wavelength tunable single-mode laser arrays based on slots

Area of Science:

• Optoelectronics
• Semiconductor Lasers
• Nanophotonics

Background:

• O-band lasers are crucial for optical communications.
• Slot gratings offer a method for wavelength control in lasers.
• Mode-hopping and side-mode suppression are key challenges in laser design.

Purpose of the Study:

• To investigate the performance of two twelve-channel arrays based on surface-etched slot gratings for O-band laser operation.
• To compare the wavelength tuning range, side-mode suppression ratio (SMSR), and output power of non-uniformly versus uniformly spaced slot gratings.
• To analyze the impact of slot spacing on laser mode stability and spectral linewidth.

Main Methods:

• Fabrication of two twelve-channel laser arrays utilizing surface-etched slot gratings.
• One array featured non-uniformly spaced slots, while the other had uniformly spaced slots.
• Characterization of laser performance including wavelength tuning range, SMSR, output power, and spectral linewidth across a temperature range of 15 °C - 60 °C.

Main Results:

• The non-uniformly spaced slot array demonstrated a wavelength tuning range exceeding 40 nm.
• This array achieved an SMSR > 40 dB and output power > 20 mW over the tested temperature range.
• The uniformly spaced array exhibited discontinuous tuning due to inadequate suppression of modes one free spectral range (FSR) away.
• Lowest measured spectral linewidths were between 2 MHz and 4 MHz.

Conclusions:

• Non-uniform slot spacing in gratings effectively suppresses unwanted modes, enabling broader and more stable wavelength tuning in O-band lasers.
• Uniform slot spacing leads to mode-hopping and limited tuning range.
• The developed non-uniform slot grating design is promising for high-performance O-band laser applications.