Abstract
Single-crystal aluminum nitride (AlN) possessing both strong Pockels and Kerr nonlinear optical effects as well as a very large band gap is a fascinating optical platform for integrated nonlinear optics. In this work, fully etched AlN-on-sapphire microresonators with a high-Q of 2.1 × 106 for the TE00 mode are firstly demonstrated with the standard photolithography technique. A near octave-spanning Kerr frequency comb ranging from 1100 to 2150 nm is generated at an on-chip power of 406 mW for the TM00 mode. Due to the high confinement, the TE10 mode also excites a Kerr comb from 1270 to 1850nm at 316 mW. In addition, frequency conversion to visible light is observed during the frequency comb generation. Our work will lead to a large-scale, low-cost, integrated nonlinear platform based on AlN.
Highlights
Integrated and miniaturized optical microresonators have a wide range of applications such as nonlinear optics, quantum electrodynamics, biochemical sensing and all-optical signal processing due to their small mode volume, high intra-cavity optical power density and strong interaction between the light field and the material [1,2,3,4]
Since the first demonstration in a silica microtoroid [5], the field of optical frequency comb (OFC) generated by cascaded four-wave mixing (FWM) in high-Q microcavities has made great progress and significantly impacted applications ranging from telecommunications and spectroscopy calibration to optical ranging and astronomy [6,7,8,9]
aluminum nitride (AlN) featuring both strong Pockels ( χ2) and Kerr ( χ3) nonlinear effects [19] has been successfully used for second-harmonic generation (SHG) [20,21], third-harmonic generation (THG) [22] and electro-optic devices [23]
Summary
Integrated and miniaturized optical microresonators have a wide range of applications such as nonlinear optics, quantum electrodynamics, biochemical sensing and all-optical signal processing due to their small mode volume, high intra-cavity optical power density and strong interaction between the light field and the material [1,2,3,4]. Various material platforms for OFC generation have been demonstrated, such as MgF2 crystal cavities [10], high index silica glass (Hydex) [11], diamond [12] and silicon [13]. Silicon based materials such as silicon nitride [14,15,16] and silicon dioxide (SiO2) [17,18] have attracted more attention due to the low propagation loss and mature manufacturing processes, in conjunction with the merits of CMOS compatibility and chip-scale integration. Red and green emissions are observed with a visible CCD camera due to the harmonic generation and sum frequency generation
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