Ultra-efficient frequency comb generation in AlGaAs-on-insulator microresonators

Abstract

†All three authors contributed equally to this work pg. 2 Recent advances in nonlinear optics have revolutionized the area of integrated photonics, providing on-chip solutions to a wide range of new applications. Currently, the state of the art integrated nonlinear photonic devices are mainly based on dielectric material platforms, such as Si3N4 and SiO2. While semiconductor materials hold much higher nonlinear coefficients and convenience in active integration, they suffered in the past from high waveguide losses that prevented the realization of highly efficient nonlinear processes on-chip. Here we challenge this status quo and demonstrate an ultra-low loss AlGaAs-on-insulator (AlGaAsOI) platform with anomalous dispersion and quality (Q) factors beyond 1.5 × 10 6 . Such a high quality factor, combined with the high nonlinear coefficient and the small mode volume, enabled us to demonstrate a record low Kerr frequency comb generation threshold of ~36 µW for a resonator with a 1 THz free spectral range (FSR), ~100 times lower compared to that in previous semiconductor platform. Combs with >250 nm broad span have been generated under a pump power lower than the threshold power of state of the art dielectric micro combs. A soliton-step transition has also been observed for the first time from an AlGaAs resonator. This work is an important step towards ultra-efficient semiconductor-based nonlinear photonics and will lead to fully integrated nonlinear photonic integrated circuits (PICs) in near future. pg. 3 The extensive research on integrated nonlinear photonics in the last few years, driven by the breakthrough of the microcomb and other on-chip nonlinear devices, has opened up many new opportunities for on-chip integrated photonics, ranging from spectroscopy to atomic clock applications [1-3]. The demand to construct efficient nonlinear devices has motivated the development of different material platforms in nonlinear photonics. A common endeavor of those efforts is the reduction of the waveguide propagation loss, which is essential to enable high Q cavities so as to enhance the build-up power in the resonators and therefore increase the efficiency of the nonlinear optical processes [4]. In this regard, silica on silicon resonators [5-7] have long been dominant offering Q factors as high as 1 billion [6]. These devices can access a wide range of nonlinear effects including microwave rate soliton microcombs [8].However, over the last 5 years, there has been remarkable progress to significantly improve the Q factors of resonators in many other nonlinear integrated optical material platforms. One example is the Si3N4 platform, which delivers high performance in Kerr comb generation on chip [9][10][11]. The Si3N4 micro-resonators have enabled the generation of efficient frequency combs with repetition rates from microwave to THz frequencies [12] and improved Q factor of beyond 30 million [13,14]. Another material, which recently attracted attention, is LiNbO3. It offers additional opportunities for integrated nonlinear...

Efficient second harmonic generation in nanophotonic GaAs-on-insulator waveguides

“…Therefore, relevant SHG technologies should either support versatile and low-loss coupling techniques or be compatible with heterogeneous integration [15,29]. For example, to add SHG functionality to photonic integrated circuit (PIC) based on mature and scalable Si photonics, it is advantageous to either deposit, grow, or bond the nonlinear material to the Si substrate [29,30].…”

Topological phases in ring resonators: recent progress and future prospects

“…The differing characteristic time scales of these nonlinear effects can lead to complex pulsating dynamics [47]. Ultrafast Kerr nonlinearities are also employed for frequency mixing applications, where the relatively uniform spacing of the ring resonances is ideal for frequency comb generation [48][49][50][51][52].…”

Research advances of ultrahigh-<italic>Q</italic> on-chip microcavity photonics

“…这主要得益于光学材 料微纳加工和半导体芯片制备工艺的进一步发展、锥 形光纤高效耦合器件的广泛应用等实验仪器和技术的 提升. 在这期间, 研究人员已经能够成功制备某些片上 超高品质因子光学微腔并用于非线性光学中的实验研 究, 例如在二氧化硅微芯圆环腔和氮化硅微环腔中实 现了受激拉曼散射 [39] 、受激布里渊散射 [40] 、三次谐 波 [41,42] [46,47] (Q>10 8 )、氮化硅微环腔 [48] (Q>10 7 )、III-V族半导体微 环腔 [49] (Q>10 6 )、铌酸锂微盘腔 [50] (Q~10 7 )、氮化铝微 环腔 [51] (Q>10 6 )等. 主要的非线性光学应用包括利用微 腔受激布里渊散射或克尔光频梳产生低噪声相干微波 信号源 [40,52] ; 利用微腔受激散射拉曼散射实现纳米尺 度单颗粒检测 [53,54] ; 利用受激布里渊散射结合Sagnac 效应精确测量地球自转 [55] ; 利用普克尔效应等实现高 速光调制器 [56] ; 利用热光效应、二次合频、四波混频 等效应实现光学隔离器 [57~59] .…”