Lithium niobate is a material that exhibits outstanding electro-optic, nonlinear optical, acousto-optic, piezoelectric, photorefractive, and pyroelectric properties. A thin-film lithium niobate photonic crystal can confine light in the sub-wavelength scale, which is beneficial to the integration of the lithium niobate on-chip device. The commercialization of the lithium niobate on insulator gives birth to the emergence of high-quality lithium niobate photonic crystals. In order to provide guidance to the research of lithium niobate photonic crystal devices, recent progress about fabrication, characterization, and applications of the thin-film lithium niobate photonic crystal is reviewed. The performance parameters of the different devices are compared.
We propose a scheme that utilizes weak-field-induced quantum beats to investigate the electronic coherences of atoms driven by a strong attosecond extreme ultraviolet (XUV) pulse. The technique involves using a strong XUV pump pulse to excite and ionize atoms and a time-delayed weak short pulse to probe the photoelectron signal. Our theoretical analysis demonstrates that the information regarding the bound states, initiated by the strong pump pulse, can be precisely reconstructed from the weak-field-induced quantum beat spectrum. To examine this scheme, we apply it to the attosecond XUV laser-induced ionization of hydrogen atoms by solving a three-dimensional time-dependent Schrödinger equation. This work provides an essential reference for reconstructing the ultrafast dynamics of bound states induced by strong XUV attosecond pulses.
In this work, we compare different methods for implementing a triplicator, a phase grating that generates three equi-intense diffraction orders. The design with optimal efficiency features a continuous phase profile, which cannot be easily reproduced, and is typically affected by quantization. We compare its performance with binary and sinusoidal phase profiles. We also analyze the effect of quantizing the phase levels. Finally, a random approach is adopted to eliminate the additional harmonic orders. In all cases, a liquid-crystal-on-silicon spatial light modulator is employed to experimentally verify and compare the different approaches.
We introduce an all-optical approach, optical parametric amplification (OPA) processor to suppress the impact of Sun outage in laser satellite communication systems, which is implemented by only one nonlinear semiconductor optical amplifier driven by both electrical and optical pumps. The optimized OPA processor, with a current of 539 mA and a pump-to-signal ratio of 16 dB, could significantly improve the signal quality by 3.5 dB in experiments for the elevation angle of Sun radiation of 0 rad. The signal quality improvement is observed in the whole range of the elevation angle, confirming the effectiveness of the proposed OPA processor in the field of Sun radiation mitigation.
Lens-free on-chip microscopy with RGB LEDs (LFOCM-RGB) provides a portable, cost-effective, and high-throughput imaging tool for resource-limited environments. However, the weak coherence of LEDs limits the high-resolution imaging, and the luminous surfaces of the LED chips on the RGB LED do not overlap, making the coherence-enhanced executions tend to undermine the portable and cost-effective implementation. Here, we propose a specially designed pinhole array to enhance coherence in a portable and cost-effective implementation. It modulates the three-color beams from the RGB LED separately so that the three-color beams effectively overlap on the sample plane while reducing the effective light-emitting area for better spatial coherence. The separate modulation of the spatial coherence allows the temporal coherence to be modulated separately by single spectral filters rather than by expensive triple spectral filters. Based on the pinhole array, the LFOCM-RGB simply and effectively realizes the high-resolution imaging in a portable and cost-effective implementation, offering much flexibility for various applications in resource-limited environments.
The compact, sensitive, and multidimensional displacement measurement device plays a crucial role in semiconductor manufacture and high-resolution optical imaging. The metasurface offers a promising solution to develop high-precision displacement metrology. In this work, we proposed and experimentally demonstrated a two-dimensional displacement (XZ) measurement device by a dielectric metasurface. Both transversal and longitudinal displacements of the metasurface can be obtained by the analysis of the interference optical intensity that is generated by the deflected light beams while the metasurface is under linearly polarized incidence. We experimentally demonstrated that displacements down to 5.4 nm along the x-axis and 0.12 µm along the z-axis can be resolved with a 900 µm × 900 µm metasurface. Our work opens up new possibilities to develop a compact high-precision multidimensional displacement sensor.
We demonstrate a high power, Er:LuAG single-longitudinal-mode laser in an anti-misaligned resonator. Based on the Faraday effect, a 1.61 W single-longitudinal-mode (SLM) laser is obtained with the double corner-cube-retroreflector (CCR) structure, and the tunable wavelength is 1649.2–1650.3 nm. Additionally, we investigate the anti-misalignment characteristics when the CCR moves and rotates along the optical axis. Furthermore, by utilizing the Er:LuAG amplifier, the maximum 2.32 W single-longitudinal-mode laser at 1649.6 nm is achieved. The beam quality factors M2 of the 2.32 W Er:LuAG single-longitudinal-mode laser are 1.23 and 1.25 along the horizontal (x) and vertical (y) directions, respectively.
Entangled photon pairs are crucial resources for quantum information processing protocols. Via the process of spontaneous parametric downconversion (SPDC), we can generate these photon pairs using bulk nonlinear crystals. Traditionally, the crystal is designed to satisfy a specific type of phase-matching condition. Here, we report controllable transitions among different types of phase matching in a single periodically poled potassium titanyl phosphate crystal. By carefully selecting pump conditions, we can satisfy different phase-matching conditions. This allows us to observe first-order Type-II, fifth-order Type-I, third-order Type-0, and fifth-order Type-II SPDCs. The temperature-dependent spectra of our source were also analyzed in detail. Finally, we discussed the possibility of observing more than nine SPDCs in this crystal. Our work not only deepens the understanding of the physics behind phase-matching conditions, but also offers the potential for a highly versatile entangled biphoton source for quantum information research.