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A laser peen forming is a sheet metal forming method using laser induced shock waves. The laser peen forming with an ultra-short-pulse laser is a kind of non-thermal and die-less forming process, and is favorable for micro forming. The authors applied the laser peen forming to the bending of pure titanium thin sheet with a picosecond laser and a femtosecond laser. The changes of bending properties with atmosphere and pulse duration were investigated. The femtosecond laser irradiation in air showed the best bending efficiency. The femtosecond laser is applicable to laser cutting, also. Some thin sheets were cut into complicated shapes and bent by laser peen forming with femtosecond laser. The combined process allowed the production of various complicated small parts.

We discuss the effect of ArF (λ laser =193 nm) and KrF (λ laser =248 nm) excimer laser irradiation of InP/InGaAs/InGaAsP quantum well (QW) microstructures on surface morphology of the top InP layer. The irradiation was carried out in air with lasers delivering up to 700 pulses of fluence from 82 to 142 mJ/cm 2 . We observe the formation of nano-cone structures having their period increasing from 450 to 1080 nm for KrF laser, and from 675 to 875 nm for ArF laser, in proportion to the laser fluence and pulse number. The chemical and structural modification of the laser irradiated surface has resulted in the enhancement of the QW photoluminescence emission up to 1.4 times when compared to the non-processed material. Thus, the excimer laser processing of the surface of InP capped InGaAs/InGaAsP QW microstructures using relatively low pulse fluence, has been found attractive for the fabrication of enhanced optical emission semiconductor devices.Keywords: InP/InGaAs/InGaAsP quantum well microstructures, excimer laser irradiation, surface morphology, nano-structure formation, atomic force microscopy, photoluminescence IntroductionLaser processing of semiconductor materials has attracted continuous interest due to its potential in delivering microfabrication solutions of interest for advanced photonic and electronic devices. Due to the relatively low thermal and chemical stability of III-V compound semiconductors, laser irradiation at a relatively moderate pulse fluence can alter the surface morphological, chemical and physical properties of these materials [1]. For instance, the formation of nano-cone arrays was observed on the surface of InGaAs cap of the InGaAs/InGaAsP/InP quantum well (QW) microstructure irradiated with an excimer laser [2]. Following the annealing in a rapid thermal annealing (RTA) furnace, the laser irradiated sites exhibited an enhanced photoluminescence (PL) emission from InGaAs QWs. The sub-micrometer surface features have also been observed on the surface of bulk InP [3] and diamond-like films [4] irradiated with femtosecond (fs) lasers, which illustrates that the formation of surface nanostructures does not require a strong thermal component typical of nanosecond lasers [5]. It has also been reported that the irradiation of bulk InP with a low fluence (F ≈ 80 mJ/cm 2 ) of a nanosecond UV laser (λ = 337 nm) leads to the formation of mounds and increased surface roughness of this material in proportion to the number of irradiating laser pulses [6].Excimer lasers offer wafer level processing and these tools have been successfully applied by the microelectronics industry for sub-micrometer resolution photolithography. We have been investigating the application of 308 [2], 248 [7] and 193 nm [8] excimers for surface modification and bandgap engineering of III-V quantum semiconductors. This approach is attractive for

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A femtosecond laser is a type of ultrashort-pulse laser. Femtosecond laser irradiation induces high-pressure plasma and shock waves at the surface of a target. Under some irradiation conditions, such shock waves are enough to deform the target plastically. Laser peen forming is a type of sheet metal forming using this deformation by shock waves. The author adopted laser peen forming using femtosecond laser for thin-sheet-metal bending. Generally, shock waves induced in air are much smaller than those induced in water, and thus; are unfavorable for plastic deformation. However, the shock waves induced by a femtosecond laser were enough to bend a thin sheet metal even in air. Elastic prebending was adopted during the process. Bending angle was increased by applying prebending. The effects of laser irradiation conditions on bending efficiency were investigated. The large spot diameter and high fluence improved bending efficiency.