optical fibers and integrated optics

UEF // University of Eastern Finland

Characterization of a ring resonatorAdvanced Laboratory Practices, 26th May 2016

Atri Halder

Optical fibers and Integrated optics

Resonance

2Guiding in optical fibers / Atri Halder, 26.05.2016

If the frequency of the applied force matches with the natural frequency of any structure, then the amplitude of the field increases after each oscillation. This phenomena is known as resonance.

Y(λ) =

Resonator


A B

Ring Resonator


Resonance condition: = N. where, L = 2πR

R is the radius of the ring resonator. is the wavelength of light coupled to the input. is the effective refractive index of the waveguide.

Full width at half maxima (FWHM)


where is the group index of the medium, r is the self coupling coefficient, a is the resonator round trip loss coefficient and is the resonance wavelength.

FWHM =

Free Spectral Range (FSR)


FSR =

Finesse


Finesse =

Quality Factor (Q-factor)


It represents the number of oscillations required by the confined optical field to get its energy reduced to 1/e of the initial energy.

Q =

Micro ring resonator


10

Specification of the ring resonator

Guiding in optical fibers / Atri Halder, 26.05.2016

Experimental setup


Result: Reference



Transmission spectrum of through port for a gap 300 nm.


Enhanced resonance for a gap of 300 nm.


Transmission spectrum of through port for a gap 400 nm.


Enhanced resonance for a gap of 400 nm.


Transmission spectrum of drop port for a gap 400 nm.


Transmission spectrum of through and drop port for a gap 400 nm.

Comparison


Comparison


Characteristics Gap of 300 nm Gap of 400 nm

FWHM 0.55 nm 0.475 nm

FSR 1.507 nm 1.526 nm

Finesse 2.74 3.21

Q-factor 3005.7 3291.25

Loss 18.40 dB/cm 15.84 dB/cm

Conclusion


• There was a high loss in between the bus and the ring.• The structure was so small that there was always a problem of coupling.

• As the gap between the bus and the ring was increased, the resonance varied a lot and we can conclude that for a gap of 400 nm the resonance was best.

• The whole experimental work was quite challenging.• Though we got a good result for different parameters of the ring resonator, we failed to generate good data for the drop port. It was due to imperfections of the structure and lot of dust particles on the sample.

Thank you!

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