Near-field characterization of 2D disk resonator on Bloch surface wave platform R.Dubey, B. Vosoughi Lahijani, E. Barakat M.-S. Kim and H. P. Herzig Optics &Photonics Technology Laboratory (OPT), École Polytechnique FÊdÊrale de Lausanne (EPFL), Rue de la Maladière 71b, Neuchâtel, Switzerland
email: richa.dubey@epfl.ch
Abstract We present the first experimental investigation of a two-dimensional (2D) disk resonator, which is fabricated on the top of Bloch surface wave (BSW) based dielectric platform. The 2D resonator has been patterned into few tens of nanometer thin layer of TiO2 deposited on the top. With the aid of multi-heterodyne scanning near field optical microscopy (MH-SNOM), we characterize the disk resonator.
Concept behind multilayer platform and BSW excitation
2D Disk resonator on BSW platform
Dispersion band diagram of multilayer (ML) platform
Advantages
2D disk resonator patterned on top of ML platform. MH-SNOM to observe the interaction of surface waves.
ďƒź Broad range of wavelength from IR to near-UV ďƒź Low Losses ďƒź Wide material choice ďƒź Narrow Resonance Dip ďƒź Works in TE and TM polarization ďƒź Simple Fabrication (PECVD)
Total Internal Reflection configuration
Near field image of wavelength scan taken by MH-SNOM Wavelength scan at through port
Wavelength scan at periphery of the disk
Full Scan at On- resonance condition Field amplitude distribution over the complete disk at On resonance (1555.4 nm)
On resonance Condition 2đ?œ‹đ?‘… ∗ đ?‘›đ?‘’đ?‘“đ?‘“ = đ?‘šđ?œ† Îť - BSWwavelength, neff - effective index of the mode propagating inside the cavity m- azimuthal mode number.
Wavelength scan were performed using tunable external cavity laser (1460 -1580 nm)
Normalized transmission spectrum at the through port and the periphery of the disk as a function of the wavelength. The field amplitude is normalized with respect to the amplitude at the input port.
The measured Q factor at through port Q = Ν0/ΔΝ 3 =2 x 10
The near field distribution around the coupling area between the waveguide and the disk for Off-resonance condition (1554.5 nm) and at On-resonance
Conclusion For the first time a 2D disk resonator has been demonstrated experimentally on BSW dielectric multilayer platform. A thin layer of TiO2 has been used as a high refractive index additional layer on the top of a dielectric periodic stack to form the 2D disk resonator. For a disk radius of 100 Âľm, measured quality factor of 2x103 can be achieved, thanks to The low loss characteristics of BSW. BSW based 2D disk resonator can find application in sensing or integrated optics. References
Acknowledgement
[1] P. Yeh, , et al., Appl. Phys. Lett. 32, 104–105, 1978 [2] T. Sfez, et al., JOSAB, vol. 27, pp. 1617-1625, 2010. [3] T. Holmgaard, et al., Opt. Express, vol. 17, p. 2968,2009. [4] A. Sinibaldi, et al., Sens. Actuators B Chem.,vol. 174, pp. 292–298, 2012.
- We acknowledge Institute of Photonics, University of Eastern Finland for the TiO2 deposition. - This project is funded by the Swiss National Science Foundation under the project number 200020_135455.