Multi-mode microcavity frequency engineering through a shifted grating in a photonic crystal ring

Area of Science:

• Photonics
• Nonlinear Optics
• Microcavity Devices

Background:

• Frequency engineering of whispering-gallery resonances is critical for microcavity nonlinear optics.
• Controlling cavity mode frequencies is essential for nonlinear optical processes.
• Conventional methods like altering cross-sectional geometry impact all modes, while grating-assisted microrings offer mode-selective control.

Purpose of the Study:

• To introduce a simple and effective approach for multi-frequency engineering in microring cavities.
• To demonstrate a method that overcomes the fabrication complexity of multi-period gratings.
• To enable nonlinear optical processes in devices not typically suited for them.

Main Methods:

• Developed a technique termed shifted grating multiple mode splitting (SGMMS).
• Introduced spatial displacement of a single-period grating on the microring's inner boundary.
• Created rotational asymmetry to frequency split multiple adjacent cavity modes.

Main Results:

• SGMMS provides multi-frequency engineering with simple implementation and no added fabrication complexity.
• Demonstrated the ability to engineer frequencies of multiple adjacent cavity modes.
• Enabled optical parametric oscillation (OPO) across a wide range of pump wavelengths in a normal-dispersion device.

Conclusions:

• SGMMS is a powerful and easily implementable technique for multi-frequency engineering in nonlinear optics.
• This method simplifies the complex grating profiles previously required for multi-frequency control.
• SGMMS expands the applicability of microcavity devices for nonlinear optical applications, such as OPO in normal-dispersion regimes.