Energy attenuations in single microfiber and double-loop cavity supported by optical substrate.

Area of Science:

• Photonics
• Materials Science
• Optical Engineering

Background:

• Silica microfibers and microcavities are key components in integrated photonic circuits.
• Understanding energy loss mechanisms is crucial for device performance and miniaturization.

Purpose of the Study:

• To characterize energy losses in single-silica microfibers and double-loop microcavities.
• To investigate the impact of bending radius on microfiber energy loss.
• To analyze transmission losses in double-loop cavities and their dependence on cavity shape.

Main Methods:

• Experimental characterization of energy losses in silica microfibers and MgF2-deposited double-loop microcavities.
• Measurement of bending loss rates and propagation loss for microfibers.
• Analysis of transmission losses during the assembly of double-loop cavities.
• Comparative study of bending losses between curved microfibers and microcavities.

Main Results:

• For microfibers with a 1.4 μm diameter, bending loss exceeds propagation loss (approx. 0.039 dB/μm) when the bending radius is below approximately 37 μm.
• Transmission loss in double-loop cavities is tunable by altering cavity shape.
• A cavity with a 30 μm radius exhibits bending loss comparable to a microfiber with 60 μm bending radii.
• Excessive bending of the input end of a cavity leads to significant output energy attenuation, deeming it unsuitable for integration.

Conclusions:

• Bending radius is a critical factor determining energy loss in silica microfibers.
• Double-loop microcavities offer a more compact structural alternative to curved microfibers for photonic circuits.
• The sensitivity of double-loop cavities to input end bending limits their applicability in certain integrated photonic applications.