Search

Generation and control of short pulse is desired for ultrafast applications. Here the authors demonstrate ultrafast pulse generation using self-evolving photonic crystal that can transition from high loss to low loss state based on dynamic dispersion compensation.

Short-wavelength lasers based on wide-bandgap GaN photonic crystals are promising for high-brightness illumination and materials processing. Here, the authors develop a nano-fabrication method for GaN/air photonic crystals, achieving high lasing operation performance in terms of output power, beam quality, and low threshold current.

1550 nm wavelength photonic-crystal surface-emitting lasers (PCSELs) are attractive for optical communication and eye-safe sensing applications. In this study, we present InP-based PCSELs featuring a double-lattice photonic-crystal structure designed for high-power single-mode operation at a wavelength of 1550 nm. These PCSELs demonstrate output powers exceeding 300 mW under continuous-wave conditions at 25 °C. Additionally, highly stable single-mode oscillation with a side-mode suppression ratio of over 60 dB is verified at temperatures from 15 °C to 60 °C. Measurement and simulation of photonic band structures reveal the impacts of the threshold gain margin and optical coupling coefficient on the single-mode stability.

Visible-wavelength GaN-based photonic-crystal surface-emitting lasers (PCSELs) have attracted attention for various applications, such as materials processing, high-brightness illuminations, and displays. In this letter, we demonstrate GaN-based PCSELs at green wavelengths. We formed a photonic crystal (PC) in p-GaN and filled holes of the PC with SiO _2 to ensure device stability. Through a current injection test under pulsed conditions and spectral analysis, we confirmed that the fabricated device possessed Γ-point single-mode oscillation at wavelengths above 505 nm. Our results have the potential to further expand the applications of PCSELs and semiconductor lasers in visible region.

Here, the authors analytically derive the general conditions for 100-W-to-1-kW-class single-mode operation in ultra-large-area (3~10 mm) photonic crystal lasers. Such high power single-mode semiconductor lasers will bring innovation to a wide variety of fields.

Beam scanning lasers are required for systems for smart mobility, object recognition, and adaptive illuminations. The authors demonstrate dually modulated photonic crystals, wherein the positions and sizes of the photonic-crystal lattice points are modulated simultaneously, to achieve mechanical-free, 2D beam scanning.

We carry out the structural design of photonic crystals to enhance the optical absorption of thin-film microcrystalline silicon (μc-Si) solar cells using two methods. First, by exhaustive search, we choose a structure with the largest absorption within the investigated patterns. Then we employ a sensitivity analysis to finely modulate the structure for further increase of the optical absorption. The obtained μc-Si solar cell structure with a photonic crystal in this work has more than twice as much optical absorption as that without a photonic crystal.

Photonic-crystal surface-emitting lasers (PCSELs) have attracted considerable attention as a novel semiconductor laser that surpasses traditional semiconductor lasers. In this review article, we review the current progress of PCSELs, including the demonstration of large-area coherent oscillation, the control of beam patterns, the demonstration of beam steering, and the realization of watt-class and high-beam-quality operation. Furthermore, we show very recent progress in the exploration of high brightness of more than 300 MW cm−2 sr−1, obtained with a high output power of about 10 W while maintaining a high beam quality M2 ~ 2. The PCSELs with such high performances are expected to be applied to a variety of fields, such as laser-based material processing, optical sensing (light-detection and ranging (LiDAR)), and lighting, as they retain the benefits of compact and high-efficiency semiconductor lasers.

We experimentally demonstrate the high-speed, on-chip wavelength switching of thermal emission in the mid-infrared region. Our device consists of multiple integrated thermal emitters of different colors, each of which is composed of quantum wells and a photonic crystal. On current injection, the device exhibits narrowband (Q>70) thermal emission with low electric power consumption. By applying a reverse bias to each section of the device, we achieve high-speed (>kHz) switching of multiple thermal emission wavelengths, opening a route towards compact, highly efficient midinfrared light sources for various sensing applications. [ABSTRACT FROM AUTHOR]

Enhancing the absorption of thin-film microcrystalline silicon solar cells at 600–1000 nm wavelengths is very important to the improvement of the energy conversion efficiency. This can be achieved by creating a large number of resonant modes utilizing two-dimensional photonic crystal band edges, which exceeds the Lambertian limit of absorption in random textures. We focus on suppressing the parasitic absorption of back-reflector metal and doped layers in photonic crystal microcrystalline silicon solar cells. We achieve a high active-area current density of 22.6 mA cm−2 for an ultrathin (∼500 nm)-film silicon layer and obtain an active-area efficiency of ∼9.1%, as independently confirmed by the CSMT of AIST. [ABSTRACT FROM AUTHOR]

The fabrication of air/semiconductor two-dimensional photonic crystal structures by air-hole-retained crystal regrowth using tertiary-butyl arsine-based metal–organic vapor-phase epitaxy for GaAs-based photonic crystal lasers is investigated. Photonic crystal air holes with filling factors of 10–13%, depths of ∼280 nm, and widths of 120–150 nm are successfully embedded. The embedded air holes exhibit characteristic shapes due to the anisotropy of crystal growth. Furthermore, a low lasing threshold of ∼0.5 kA/cm2 is achieved with the fabricated structures. [ABSTRACT FROM AUTHOR]