Ultra-low loss visible light waveguides for integrated atomic, molecular, and quantum photonics

Abstract

Atomic, molecular and optical (AMO) visible light systems are the heart of precision applications including quantum, atomic clocks and precision metrology. As these systems scale in terms of number of lasers, wavelengths, and optical components, their reliability, space occupied, and power consumption will push the limits of using traditional laboratory-scale lasers and optics. Visible light photonic integration is critical to advancing AMO based sciences and applications, yet key performance aspects remain to be addressed, most notably waveguide losses and laser phase noise and stability. Additionally, a visible light integrated solution needs to be wafer-scale CMOS compatible and capable of supporting a wide array of photonic components. While the regime of ultra-low loss has been achieved at telecommunication wavelengths, progress at visible wavelengths has been limited. Here, we report the lowest waveguide losses and highest resonator Qs to date in the visible range, to the best of our knowledge. We report waveguide losses at wavelengths associated with strontium transitions in the 461 nm to 802 nm wavelength range, of 0.01 dB/cm to 0.09 dB/cm and associated intrinsic resonator Q of 60 Million to 9.5 Million, a decrease in loss by factors of 6x to 2x and increase in Q by factors of 10x to 1.5x over this visible wavelength range. Additionally, we measure an absorption limited loss and Q of 0.17 dB/m and 340 million at 674 nm. This level of performance is achieved in a wafer-scale foundry compatible Si3N4 platform with a 20 nm thick core and TEOS-PECVD deposited upper cladding oxide, and enables waveguides for different wavelengths to be fabricated on the same wafer with mask-only changes per wavelength. These results represent a significant step forward in waveguide platforms that operate in the visible, opening up a wide range of integrated applications that utilize atoms, ions and molecules including sensing, navigation, metrology and clocks.

Integrating planar photonics for multi-beam generation and atomic clock packaging on chip

“…Importantly, this is not a fundamental limitation of the relatively compact emitter technologies, but a technical limitation of long waveguides. It can be overcome in the future devices by adding dedicated waveguiding layers using materials with low loss in the blue or thin Si 3 N 4 waveguides pushing the mode energy out into the low-loss oxide cladding 35 . Some of our initial tests demonstrate exceptionally reduced propagation losses with 30 nm thick Si 3 N 4 waveguides (see Fig.…”

Integrated stabilized lasers and circuits for atom cooling, trapping, and interrogation

“…Taking inspiration from these systems, we leverage the properties of nonlinear and ultra-low loss resonators fabricated using the silicon nitride (Si3N4) waveguide platform [26] components needed for AMO laser and optical systems. With losses as low as 0.034 dB/m and transparency from 405 nm through the infrared (IR) [16,17], the Si3N4 waveguide platform is a versatile solution for integrating stable lasers. Additionally, the Si3N4 waveguide platform is wafer-scale and CMOS foundry compatible, enabling integration of a wide variety of photonic elements at the chip-scale.…”

“…Today's optics infrastructure presents challenges to scaling the number of atoms, ions or qubits, in order to improve the sensitivity of a quantum sensor or computational complexity of a quantum computer. For visible light AMO systems, waveguide loss is paramount to the preservation of photons [16] and resonator Q plays a critical role in laser linewidth narrowing, phase noise reduction and filtering [17]. Photonic integration can address these requirements [18] and key functions including photon routing, optical filtering [19], free-space beam formation [20,21], and hybrid tunable [22] and ultra-low linewidth lasers [23,24].…”

Ultra-low loss quantum photonic circuits integrated with single quantum emitters

“…The ULLWs consist of a high-aspect ratio Si 3 N 4 core, with a thickness of 40 nm and width of 2 μm, buried under 1 μm SiO 2 upper cladding layer. The top cladding thickness is chosen to ensure a weakly confined single transverse-electric (TE) guided mode with low propagation losses in the 900 nm wavelength band 31 . The on-chip single-photon source consists of a straight GaAs nanowaveguide with embedded InAs self-assembled QDs followed by an adiabatic mode transformer, a geometry that has been shown to allow efficient coupling of QD emission directly into air-clad Si 3 N 4 ridge waveguides 25,32 .…”