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： A dynamically-modulated ring system with frequency as a synthetic dimension has been shown to be a powerful platform to do quantum simulation and explore novel optical phenomena. Here we propose synthetic honeycomb lattice in a one-dimensional ring array under dynamic modulations, with the extra dimension being the frequency of light. Such system is highly re-configurable with modulation. Various physical phenomena associated with graphene including Klein tunneling, valley-dependent edge states, effective magnetic field, as well as valley-dependent Lorentz force can be simulated in this lattice, which exhibits important potentials for manipulating photons in different ways. Our work unveils a new platform for constructing the honeycomb lattice in a synthetic space, which holds complex functionalities and could be important for optical signal processing as well as quantum computing.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Constructions of synthetic lattices in photonics attract growingly attentions for exploring interesting physics beyond the geometric dimensionality, among which modulated ring resonator system has been proved as a powerful platform to create different kinds of connectivities between resonant modes along the synthetic frequency dimension with many theoretical proposals. Various experimental realizations are investigated in a single ring resonator, while building beyond simple synthetic lattices in multiple rings with different types remains lacking, which desires to be accomplished as an important step further. Here, we implement the experimental demonstration of generating the one-dimensional Lieb lattice along the frequency axis of light, realized in two coupled ring resonators while the larger ring undergoing dynamic modulation. Such synthetic photonic structure naturally exhibits the physics of flat band. We show that the time-resolved band structure read out from the drop-port output of the excited ring is the intensity projection of the band structure onto specific resonant mode in the synthetic momentum space, where gapless flat band, mode localization effect, and flat to non-flat band transition are observed in experiments and verified by simulations. Our work gives a direct evidence for the constructing synthetic Lieb lattice with two rings, which hence makes a solid step towards experimentally constructing more complicated lattices in multiple rings associated with synthetic frequency dimension.
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