RESUMEN
In this paper, we demonstrated a miniaturized diffractive/refractive hybrid system based on a diffractive optical element and three refractive lenses to achieve solar-blind ultraviolet imaging within a range of 240-280â nm. We experimentally demonstrate the optical system has both outstanding resolution and excellent imaging capability. The experiments demonstrate that the system could distinguish the smallest line pair with a width of 16.7â µm. The modulation transfer function (MTF) at the target maximum frequency (77 lines pair/mm) is great than 0.76. The strategy provides significant guidance for the mass production of solar-blind ultraviolet imaging systems towards miniaturization and lightweight.
RESUMEN
Graphene is a promising candidate for the next-generation infrared array image sensors at room temperature due to its high mobility, tunable energy band, wide band absorption, and compatibility with complementary metal oxide semiconductor process. However, it is difficult to simultaneously obtain ultrafast response time and ultrahigh responsivity, which limits the further improvement of graphene photoconductive devices. Here, a novel graphene/C60 /bismuth telluride/C60 /graphene vertical heterojunction phototransistor is proposed. The response spectral range covers 400-1800 nm; the responsivity peak is 106 A W-1 ; and the peak detection rate and peak response speed reach 1014 Jones and 250 µs, respectively. In addition, the regulation of positive and negative photocurrents at a gate voltage is characterized and the ionization process in impurities of the designed phototransistor at a low temperature is analyzed. Tunable bidirectional response provides a new degree of freedom for phototransistors' signal resolution. The analysis of the dynamic change process of impurity energy level is conducted to improve the device's performance. From the perspective of manufacturing process, the ultrathin phototransistor (20-30 nm) is compatible with functional metasurface to realize wavelength or polarization selection, making it possible to achieve large-scale production of integrated spectrometer or polarization imaging sensor by nanoimprinting process.
RESUMEN
Monolithic integrated mode converters with high integration are essential to photonic integrated circuits (PICs), and they are widely used in next-generation optical communications and complex quantum systems. It is expected that PICs will become more miniaturized, multifunctional, and intelligent with the development of micro/nano-technology. The increase in design space makes it difficult to realize high-performance device design based on traditional parameter sweeping or heuristic design, especially in the optimal design of reconfigurable PIC devices. Combining the mode coupling theory and adjoint calculation method, we proposed a design method for a switchable mode converter. The device could realize the transmission of TE0 mode and the conversion from TE0 to TE1 mode with a footprint of 0.9 × 7.5 µm2 based on the phase change materials (PCMs). We also found that the mode purity could reach 78.2% in both states at the working wavelength of 1.55 µm. The designed method will provide a new impetus for programmable photonic integrated devices and find broad application prospects in communication, optical neural networks, and sensing.
RESUMEN
Integration of optical waveguide and subwavelength structure may help address the problems of large footprint, low robustness, and small operation bandwidth, those of that are typically inborn in traditional integrated optical devices. Here, a design method of an ultra-compact small footprint lens is proposed. Combing particle swarm optimization (PSO) algorithm with spatial multiplexing technology, we successfully integrated two- and four-step varifocal lenses on SOIs chips with small footprint of 35×35 µm2, non-mechanically leading to 2.5× and 3.4× zoom capacity, respectively. The proposed designed method may shed a new light on compact on-chip display devices and offer an alternative approach to design integrated optical communication with high information storage capacity.
RESUMEN
A metasurface combined with phase-change material Ge2Sb2Te5 (GST) is proposed to act as a switchable wave plate to adjust spin-orbit interactions (SOIs), so that the polarization and phase of the reflected light are simultaneously manipulated. A converter, which could act as a quarter-wave plate or three-quarter-wave plate when the GST layer is in the amorphous or crystalline state, and a switch, which could act as a mirror (corresponding to the "OFF" state of SOIs) or half-wave plate (corresponding to the "ON" state of SOIs) when the GST layer is in the amorphous or crystalline state, are designed, respectively. Consequently, a convertible vectorial beams converter, which could generate radial or azimuthal polarization, is designed when the GST layer is in the amorphous or crystalline state. In addition, a switchable vortex beam generator could realize orbital angular momentum with topological charge l=±2 when the GST layer changes from amorphous to the crystalline state. The designed metasurface could offer a promising route for high-efficiency reconfigurable devices and encrypted optical communications.
