分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： On-chip efficient nonlinear functions are instrumental in escalating the utilities and performance of photonic integrated circuits (PICs), especially for a wide range of classical and quantum applications, such as tunable coherent radiation, optical frequency conversion, spectroscopy, quantum science, etc. Lithium tantalate (LT) has been widely used in nonlinear wavelength converters, surface acoustic wave resonators, and electro-optic, acoustic-optic devices owing to its excellent optical properties. Here, we fabricated a Z-cut lithium tantalate on insulator (LTOI) microdisk with high quality(Q) factors in both telecom (10$^{6}$) and visible (10$^{5}$) bands by optimizing the fabrication. With the Q factor of the LTOI microdisk increasing, we can obtain higher pump light intensity in the cavity which is beneficial to get more optical nonlinear effect easily. By making use of the mode phase matching of interacting waves and inputting high pump power, we experimentally observed on-chip near-infrared light, visible (red, green), and ultraviolet (UV) from microresonator-based $ \chi^{(2)}-\chi^{(2)}$, $ \chi^{(2)}-\chi^{(3)}$, and $\chi^{(2)}$ nonlinear processes such as cascaded four-wave mixing (cFWM), cascaded sum-frequency generation (cSFG), third harmonic generation (THG), second harmonic generation (SHG). It is believed that the LTOI can support a variety of on-chip optical nonlinear processes, which heralds its new application potential in integrated nonlinear photonics.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Integrated optical amplifiers and light sources are of great significance for photonic integrated circuits (PICs) and have attracted many research interests. Doping rare-earth ions in materials as a solution to realize efficient optical amplifiers and lasing has been investigated a lot. We investigate the erbium-doped lithium niobate on insulator (LNOI). Here, spiral waveguide amplifiers were fabricated on a 1-mol\% erbium-doped LNOI by CMOS-compatible technique. We demonstrated a maximum internal net gain of 8.3 dB at 1530 nm indicating a net gain per unit length of 15.6 dB/cm with a compact spiral waveguide of 5.3 mm length and $ \sim $0.06 mm$ ^{2} $ footprint. The erbium-doped integrated lithium niobate spiral waveguide amplifiers would pave the way in the PICs of the lithium niobate platform, especially in achieving efficient integration of active and passive devices on a lithium niobate thin film, which will make full use of its excellent physical properties such as remarkable photoacoustic, electro-optic, and piezoelectric characteristics.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： In this work, a doubly resonant photonic crystal (PhC) cavity using the merged bound states in the continuum (BICs) is proposed to obtain a higher second harmonic generation (SHG) efficiency. Firstly by scanning geometry parameters the accidental BICs and a band-edge mode outside the light cone can be obtained. Then as the lattice constant or the thickness of the slab is adjusted the accidental BICs will merge. A supercell with large and small holes is constructed and the band-edge mode outside the light cone can be mode-matched with the merged BICs mode. Finally the heterostructure PhC cavity is designed. The merged BICs show a high quality factor for the photonic crystal with finite size. Consequently, the SHG efficiency of the lattice constant near merged BICs of ~6000% W-1 is higher than the one of the isolated BIC.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Erbium-doped lithium niobate on insulator (LNOI) laser plays an important role in the complete photonic integrated circuits (PICs). Here, we demonstrate an integrated tunable whisper galley single mode laser (WGSML) by making use of a pair of coupled microdisk and microring on LNOI. A 974 nm single-mode pump light can have an excellent resonance in the designed microdisk, which is beneficial to the whisper gallery mode (WGM) laser generation. The WGSML at 1560.40 nm with a maximum 31.4 dB side mode suppression ratio (SMSR) has been achieved. By regulating the temperature, WGSMLs output power increased and the central wavelength can be changed from 1560.30 nm to 1560.40 nm. What's more, 1560.60 nm and 1565.00 nm WGSMLs have been achieved by changing the coupling gap width between microdisk and microring. We can also use the electro-optic effect of LNOI to obtain more accurate adjustable WGSMLs in further research.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Due to their capacity for non-classical light generation, high-efficiency second-order nonlinear parametric processes play an important role in quantum photonic technology, and chip-scale realization of these processes is recognized as the key to building efficient light sources for integrated quantum photonic circuits. To achieve ultra-high nonlinear conversion efficiency, traditional method uses quasi-phase matching (QPM) technology. However, QPM requires electric field poling, which is incompatible with the CMOS fabrication process, and this hinders the wafer-scale production of integrated photonic circuits. In this paper, we demonstrate efficient spontaneous quasi-phase matched (SQPM) frequency conversion in a micro-racetrack resonator. Our approach does not involve poling, but exploits the anisotropy of the ferroelectric crystals to allow the phase-matching condition to be fulfilled spontaneously as the TE-polarized light circulates in a specifically designed racetrack resonator. SQPM second harmonic generation is observed with a normalized intracavity conversion efficiency of 0.85%/W, corresponding to the 111st-order QPM. This could theoretically reach 186,000%/W by first-order QPM. In this case such high intracavity conversion efficiency can be implemented in practice with an optimized outward coupling. Our configurable SQPM approach will benefit the application of nonlinear frequency conversion in chip-scale integrated photonics with CMOS-compatible fabrication processes, and is applicable to other on-chip nonlinear processes such as quantum frequency conversion or frequency-comb generation.
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