In this talk, we present watt-class high-power, high-beam-quality operation of GaN-based photonic crystal lasers (PCSELs) at blue wavelengths, having a low threshold current density. First, we design a device layer structure to enhance the 2D photonic-crystal resonant effect in GaN-based materials, considering their low refractive index contrast. Next, we develop a new nano-fabrication method for realizing GaN/air structures with sufficiently small disorders. Then, we introduce an asymmetric unit cell based on a double-lattice structure in order to enhance the extraction efficiency of light toward the optical facet for high-power operation. Based on these optimizations, we successfully develop GaN PCSELs with high, watt-class (>1 W) output power and circular, single-lobed beam with a very narrow (~0.2°) divergence angle. In addition, we demonstrate CW operation with a high output power (~320 mW) and a high beam quality (M2~1).
We have demonstrated a single-mode lasing with a narrow single-lobe beam emission from InP-based double-lattice photonic-crystal surface-emitting lasers (PCSELs) in a wide temperature range from 25°C to 80°C under CW condition. A high output power of 240 mW is achieved at a temperature of 25°C. The lasing occurs even at a high temperature of 80°C, and the output power is 48 mW. The single-mode lasing and the narrow single-lobe beam with divergence angle below 1.5°, which is a unique feature of PCSELs, are maintained even at a high temperature of 80°C.
We report on photonic crystal lasers (PCSELs) with high power and high beam quality. The PCSELs have been developed with AI-assisted technologies. The developed devices with a 500µm diameter successfully oscillated with a high, 10W-class peak output power and a very narrow divergence angle of 0.1°. This fact indicates that the devices operate in a complete single lateral and longitudinal mode even over the large area of 500µm diameter. The devices have been installed in time-of-flight LiDAR system. Very high-resolution operation has been successfully realized even though a lens system is not utilized, clearly demonstrating the advantage of high-brightness PCSELs.
Recently, W-class photonic-crystal surface-emitting lasers (PCSELs) with both a single spectrum and narrow spot beam pattern are reported. These highly coherent PCSEL properties cause a highly bright laser light that is useful for various applications. To improve the PCSEL output power, it is important to enlarge the emitting area to reduce the heat generation effect. However, multi-mode oscillation occurs in a broad emitting area because the difference in the threshold gain between the fundamental and higher modes becomes narrower as the emitting area is broadened. In this work, we fabricate PCSELs with double-hole lattice points that decrease the optical confinement to prevent multi-mode oscillation. The fabricated device, consisting of an AlGaAs/InGaAs material system designed to be oscillated at a wavelength of 940nm, has an emitting area of 300 × 300 μm2. In a square lattice photonic crystal whose lattice period equals the lasing wavelength embedded in PCSELs, the distance between the centers of the double hole is set to one quarter of the lasing wavelength to decrease in-plane coupling caused by interference. We confirm that this device is oscillated at the Γ point of band edge A in the photonic band structure. The peak power is more than 5 W under pulse operation at 10 A. The device has a narrow beam divergence of less than 1° and single lobe spectrum in spite of the broad emitting area, so these double-hole lattice points are an effective structure to improve the PCSEL output power.
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