Ultrahigh polarization-stable narrow-linewidth grating coupled-cavity vertical-cavity surface-emitting laser for...

Area of Science:

• Optoelectronics
• Atomic Physics
• Laser Technology

Background:

• Vertical-cavity surface-emitting lasers (VCSELs) are promising for all-optical coherent population trapping (CPT) atomic clocks.
• VCSEL polarization instability and broad linewidths limit atomic clock performance.
• Mode competition in VCSELs causes phase noise, polarization instability, and limits linewidth reduction.

Purpose of the Study:

• To address fundamental constraints of polarization instability and broad linewidth in VCSELs for atomic clocks.
• To propose and experimentally verify a novel GC-VCSEL design for enhanced stability and narrow linewidth.
• To enable high-performance chip-scale atomic clocks (CSACs).

Main Methods:

• Design of a guide-mode resonant subwavelength grating coupling cavity VCSEL (GC-VCSEL).
• Utilized a grating waveguide-coupled cavity to favor transverse electric (TE) modes over transverse magnetic (TM) modes.
• Implemented a dual-cavity optical feedback system for linewidth compression.

Main Results:

• Achieved a polarization suppression ratio of nearly 30 dB, even in high-temperature environments.
• Demonstrated stable single-mode performance across variations in temperature and current.
• Maintained an excellent current wavelength coefficient of 0.33 nm/mA at 80 °C.

Conclusions:

• The GC-VCSEL design effectively suppresses polarization instability and reduces linewidth.
• The device exhibits robust performance suitable for demanding applications like CSACs.
• GC-VCSELs represent a significant advancement for next-generation atomic clock technology.