Laser induced periodic surface structures(LIPSS)represent a kind of top down approach to produce highly reproducible nano/microstructures without going for any sophisticated process of lithography.This method is much ...Laser induced periodic surface structures(LIPSS)represent a kind of top down approach to produce highly reproducible nano/microstructures without going for any sophisticated process of lithography.This method is much simpler and cost effective.In this work,LIPSS on Si surfaces were generated using femtosecond laser pulses of 800 nm wavelength.Photocatalytic substrates were prepared by depositing TiO2 thin films on top of the structured and unstructured Si wafer.The coatings were produced by sputtering from a Ti target in two different types of oxygen atmospheres.In first case,the oxygen pressure within the sputtering chamber was chosen to be high(3×10^–2 mbar)whereas it was one order of magnitude lower in second case(2.1×10^–3 mbar).In photocatalytic dye decomposition study of Methylene blue dye it was found that in the presence of LIPSS the activity can be enhanced by 2.1 and 3.3 times with high pressure and low pressure grown TiO2 thin films,respectively.The increase in photocatalytic activity is attributed to the enlargement of effective surface area.In comparative study,the dye decomposition rates of TiO2 thin films grown on LIPSS are found to be much higher than the value for standard reference thin film material Pilkington Activ^TM.展开更多
Silicon-based photodetectors are experiencing significant demand for realizing infrared photodetection,night vision imaging,and ultraviolet-enhanced monitoring and communication.Recently,femtosecond-laser(fs-laser)hyp...Silicon-based photodetectors are experiencing significant demand for realizing infrared photodetection,night vision imaging,and ultraviolet-enhanced monitoring and communication.Recently,femtosecond-laser(fs-laser)hyperdoped silicon photodetectors have gained attention as promising alternatives to conventional silicon-based devices,owing to their exceptional properties,including high detectivity at low operating bias,broadband response spectrum beyond the bandgap limitation,wide operational temperature range,and ultrahigh dynamic range.Despite these advantages,the practical application of fs-laser hyperdoped devices has been hindered by challenges such as uneven surface structures and numerous lattice defects,which impede industrialization,chip integration,and ultraviolet photodetection performance.In this study,we present,to our knowledge,a novel design of flat fs-laser hyperdoped silicon materials and photodetectors tailored for complementary metal-oxide-semiconductor(CMOS)compatibility.A key innovation lies in the reduction of surface structure dimensions by three orders of magnitude,enabling the integration of fs-laser hyperdoped silicon as a photodetection layer in back-illuminated CMOS devices.The proposed photodetector achieves a peak responsivity of120.07 A/W and a specific detectivity of 1.27×10^(14)Jones at 840 nm,marking the highest performance reported for fs-laser hyperdoped silicon photodetectors.Furthermore,it demonstrates ultraviolet enhancement and sub-bandgap infrared photodetection simultaneously,with responsivities exceeding 10 A/W across a broad spectrum from 350 to 1170 nm at 5 V.This breakthrough not only paves the way for fs-laser hyperdoped silicon in array photodetection but also facilitates its integration with silicon-based chip fabrication processes,addressing critical bottlenecks for industrialization and advancing the field of silicon photonics.展开更多
The inverse Faraday effect induced in magnetic films by ultrashort laser pulses allows excitation and control of spins at gigahertz and sub-terahertz frequencies. The frequency of the optically excited magnetization p...The inverse Faraday effect induced in magnetic films by ultrashort laser pulses allows excitation and control of spins at gigahertz and sub-terahertz frequencies. The frequency of the optically excited magnetization precession is easily tunable by the external magnetic field. On the other hand, the initial phase of the precession marginally depends on the magnetic field. Here we demonstrate an approach for the control of the precession phase by variation of the pump beam direction. In particular, we consider the case when the magnetization precession is excited by obliquely incident pump pulses in a magnetic dielectric film placed in the in-plane magnetic field.Theoretical consideration predicts that the initial phase should appear for a non-zero in-plane component of the pump wavevector orthogonal to the external magnetic field. Experimental studies confirm this conclusion and reveal that the phase grows with increase of the in-plane wavevector component. Variation of phase by 15 deg is demonstrated. Potentially, the phase could be changed even more pronouncedly by more than 90 deg. This work provides a simple way for additional manipulation with optically excited magnetization dynamics, which is of importance for different spintronic applications.展开更多
基金Deutsche Forschungsgemeinschaft (DFG), Germany (Grant number GR 1782/12)Science and Engineering Research Board (SERB), India (Grant number EMR/2015/001175)
文摘Laser induced periodic surface structures(LIPSS)represent a kind of top down approach to produce highly reproducible nano/microstructures without going for any sophisticated process of lithography.This method is much simpler and cost effective.In this work,LIPSS on Si surfaces were generated using femtosecond laser pulses of 800 nm wavelength.Photocatalytic substrates were prepared by depositing TiO2 thin films on top of the structured and unstructured Si wafer.The coatings were produced by sputtering from a Ti target in two different types of oxygen atmospheres.In first case,the oxygen pressure within the sputtering chamber was chosen to be high(3×10^–2 mbar)whereas it was one order of magnitude lower in second case(2.1×10^–3 mbar).In photocatalytic dye decomposition study of Methylene blue dye it was found that in the presence of LIPSS the activity can be enhanced by 2.1 and 3.3 times with high pressure and low pressure grown TiO2 thin films,respectively.The increase in photocatalytic activity is attributed to the enlargement of effective surface area.In comparative study,the dye decomposition rates of TiO2 thin films grown on LIPSS are found to be much higher than the value for standard reference thin film material Pilkington Activ^TM.
基金supported by the National Key Research and Development Program of China(No.2024YFA1409500)the National Natural Science Foundation of China(Nos.12474344,12204141,and 62105362)the 111 Project(No.B23045)。
文摘Silicon-based photodetectors are experiencing significant demand for realizing infrared photodetection,night vision imaging,and ultraviolet-enhanced monitoring and communication.Recently,femtosecond-laser(fs-laser)hyperdoped silicon photodetectors have gained attention as promising alternatives to conventional silicon-based devices,owing to their exceptional properties,including high detectivity at low operating bias,broadband response spectrum beyond the bandgap limitation,wide operational temperature range,and ultrahigh dynamic range.Despite these advantages,the practical application of fs-laser hyperdoped devices has been hindered by challenges such as uneven surface structures and numerous lattice defects,which impede industrialization,chip integration,and ultraviolet photodetection performance.In this study,we present,to our knowledge,a novel design of flat fs-laser hyperdoped silicon materials and photodetectors tailored for complementary metal-oxide-semiconductor(CMOS)compatibility.A key innovation lies in the reduction of surface structure dimensions by three orders of magnitude,enabling the integration of fs-laser hyperdoped silicon as a photodetection layer in back-illuminated CMOS devices.The proposed photodetector achieves a peak responsivity of120.07 A/W and a specific detectivity of 1.27×10^(14)Jones at 840 nm,marking the highest performance reported for fs-laser hyperdoped silicon photodetectors.Furthermore,it demonstrates ultraviolet enhancement and sub-bandgap infrared photodetection simultaneously,with responsivities exceeding 10 A/W across a broad spectrum from 350 to 1170 nm at 5 V.This breakthrough not only paves the way for fs-laser hyperdoped silicon in array photodetection but also facilitates its integration with silicon-based chip fabrication processes,addressing critical bottlenecks for industrialization and advancing the field of silicon photonics.
文摘The inverse Faraday effect induced in magnetic films by ultrashort laser pulses allows excitation and control of spins at gigahertz and sub-terahertz frequencies. The frequency of the optically excited magnetization precession is easily tunable by the external magnetic field. On the other hand, the initial phase of the precession marginally depends on the magnetic field. Here we demonstrate an approach for the control of the precession phase by variation of the pump beam direction. In particular, we consider the case when the magnetization precession is excited by obliquely incident pump pulses in a magnetic dielectric film placed in the in-plane magnetic field.Theoretical consideration predicts that the initial phase should appear for a non-zero in-plane component of the pump wavevector orthogonal to the external magnetic field. Experimental studies confirm this conclusion and reveal that the phase grows with increase of the in-plane wavevector component. Variation of phase by 15 deg is demonstrated. Potentially, the phase could be changed even more pronouncedly by more than 90 deg. This work provides a simple way for additional manipulation with optically excited magnetization dynamics, which is of importance for different spintronic applications.
