1.4 million Q factor Si3N4 micro-ring resonator at 780 nm wavelength for chip-scale atomic systems.

Martin Sinclair,Douglas J Paul,Kevin Gallacher,Euan Mcbrearty,Ross W Millar,Marc Sorel,Joseph C Bayley,Stefan Hild

doi:10.1364/oe.381224

Abstract

A silicon nitride micro-ring resonator with a loaded Q factor of 1.4 × 106 at 780 nm wavelength is demonstrated on silicon substrates. This is due to the low propagation loss waveguides achieved by optimization of waveguide sidewall interactions and top cladding refractive index. Potential applications include laser frequency stabilization allowing for chip-scale atomic systems targeting the 87Rb atomic transition at 780.24 nm. The temperature dependent wavelength shift of the micro-ring was determined to be 13.1 pm/K indicating that a minimum temperature stability of less than ±15 mK is required for such devices for wavelength locking applications. If a polyurethane acrylate top cladding of an optimized thickness is used then the micro-ring could effectively be athermal, resulting in reduced footprint, power consumption, and cost of potential devices.

Highlights

High-Q factor optical micro-ring resonators have a wide range of applications such as serving as filters, delay lines and switches [1], external cavity frequency reference for diode lasers [2], integrated laser cavity coupled to a gain medium [3], source of frequency comb generation [4], source of entangled photon pairs [5], or the sensing element for resonant optical gyroscope [6]
We demonstrate micro-ring resonators with Q factors up to 1.4 × 106 at 780 nm developed in a 200 nm thick Si3N4 photonic platform on 150 mm diameter silicon substrates
Micro-ring resonators have been fabricated in a 200 nm thick Si3N4 photonics platform with Q factors up to 1.4 × 106 at 780 nm wavelength

Summary

Introduction

High-Q factor optical micro-ring resonators have a wide range of applications such as serving as filters, delay lines and switches [1], external cavity frequency reference for diode lasers [2], integrated laser cavity coupled to a gain medium [3], source of frequency comb generation [4], source of entangled photon pairs [5], or the sensing element for resonant optical gyroscope [6]. Higher Q factors have been demonstrated from a range of lower refractive index materials where the losses can be reduced significantly such as silicon nitride where Q factors are 6.7 × 107 [8] for large modal overlapping waveguides and 8.1 × 107 for low modal overlaps with waveguides [9]. As the wavelength is reduced, the scattering losses in waveguides increase significantly as a function of the inverse of the wavelength [14,15] resulting in significantly lower micro-ring Q factors close to 780 nm, see Table 1

Methods

Results

Conclusion