Second-harmonic generation using 4-quasi-phasematching in a GaAs whispering-gallery-mode microcavity.

Area of Science:

• Solid State Physics
• Nonlinear Optics
• Materials Science

Background:

• Quasi-phasematching is crucial for efficient optical frequency conversion.
• Traditional methods like poling or domain inversion are complex and costly.
• Materials with specific crystal symmetries offer an alternative route to quasi-phasematching.

Purpose of the Study:

• To demonstrate quasi-phasematching in a whispering-gallery-mode microcavity using inherent crystal symmetry.
• To achieve efficient second-harmonic generation in a micro-scale device.
• To explore the potential of such devices for integrated photonics.

Main Methods:

• Utilized the 4 crystal symmetry of Gallium Arsenide (GaAs) microdisks.
• Employed whispering-gallery-mode microdisk resonators for resonant field enhancement.
• Coupled light into a 5-μm diameter microdisk using a tapered fiber.

Main Results:

• First experimental observation of second-harmonic generation via 4-quasi-phasematching in a microcavity.
• Achieved a normalized conversion efficiency of approximately 5 × 10⁻⁵ mW⁻¹.
• Simulations predicted a normalized conversion efficiency of approximately 3 × 10⁻³ mW⁻¹ when accounting for scattering losses.

Conclusions:

• The 4 crystal symmetry of GaAs enables efficient quasi-phasematching for optical frequency conversion.
• Whispering-gallery-mode microdisks offer a compact and efficient platform for nonlinear optics.
• These findings open possibilities for integrated photonic circuits, compact frequency converters, and novel light sources.