Laser Pulse Width Research Articles

Highly Collimated Monochromatic X-rays Generated by Collision of High-Energy Electrons with Tightly Focused Linearly Polarized Laser Pulse

This article delves into the generation and modulation process of X-rays as high-energy photon sources. Using the principles of classical electrodynamics, this study enables nonrelativistic short pulse lasers to collide with high-energy electrons while the collision center is away from the focal point. This scattering method may produce X-rays with good collimation and monochromaticity, and it progressively approaches inverse Thomson scattering. We studied and analyzed the effects of different electron characteristics and laser parameter settings on the high-energy angular distribution and spectrum of X-rays, especially the setting of the collision center and initial electron velocity, as well as the setting of laser intensity and pulse width. Linear polarized laser pulses with relativistic intensity can generate discrete supercontinuum X-rays with spectral distortion. In addition, the relationships between electronic and laser properties and radiation energy were also studied. Our research can provide valuable insights for manipulating collimated or distorted, monochromatic, or tunable X-rays, as well as understanding their properties.

Effects of machining parameters on Ni-Mn-Ga-based alloys for fabrication of multifunctional micro devices using femtosecond pulse width laser

Ni-Mn-Ga-based magnetic shape memory (MSM) alloy single crystals are known for their large magnetic-field-induced strain (MFIS). This quality makes them a promising material for use in micro actuators and devices. However, the manufacturing of single-crystal-based Ni-Mn-Ga micro actuators is challenging due to their high brittleness and other material properties – numerous machining techniques that are successfully used for the deep engraving of conventional engineering materials cannot be directly applied to Ni-Mn-Ga-based alloys. Nevertheless, previous studies have shown that a femtosecond pulse width laser (FPWL) can be successfully utilized for the defect-free micromachining various materials. This work studies the effects of different engraving parameters and introduces a novel scanning-based method for the deep micromachining of Ni-Mn-Ga-based MSM alloys with maximum surface quality. Results show that a 4-layer strategy with a 0.01 mm hatch distance provides excellent machining in terms of surface quality and dimensional accuracy. This study can be utilized within design stages to estimate minimum margin based on required machined depth and avoid defects that occur in the sample preparation stage. Additionally, evolution of structures generated by FPWL machining are characterized. The results highlight how FPWL can be considered a highly capable process for the micromachining and surface structuring of Ni-Mn-Ga-based single crystals for manufacturing multifunctional MSM microdevices.

Periodical Ultra-Modulation of Broadened Laser Spectra in Dielectrics at Variable Ultrashort Laser Pulsewidths: Ultrafast Plasma, Plasmonic and Nanoscale Structural Effects

Self-phase modulation (SPM) broadening of prompt laser spectra was studied in a transmission mode in natural and synthetic diamonds at variable laser wavelengths (515 and 1030 nm), pulse energies and widths (0.3–12 ps, positively chirped pulses), providing their filamentary propagation. Besides the monotonous SPM broadening of the laser spectra versus pulse energy, which was more pronounced for the (sub)picosecond pulsewidths and more nitrogen-doped natural diamond with its intra-gap impurity states, periodical low-frequency modulation was observed in the spectra at the shorter laser pulsewidths, indicating dynamic Bragg filtering of the supercontinuum due to ultrafast plasma and nanoplasmonic effects. Damping of broadening and ultra-modulation for the longer picosecond pulsewidths was related to the thermalized electron-hole plasma regime established for the laser pulsewidths longer, than 2 ps. Unexpectedly, at higher pulse energies and corresponding longer, well-developed microfilaments, the number of low-intensity, low-frequency sideband spectral modulation features counterintuitively increases, thus indicating dynamic variation of the periods in the longitudinal plasma Bragg gratings along the filaments due to prompt secondary laser–plasmon interactions. The underlying sub- and/or near-wavelength longitudinal nanoscale Bragg gratings produced by femtosecond laser pulses in this regime could be visualized in less hard lithium niobate by atomic force microscopy cross-sectional analysis in the correlation with the corresponding sideband spectral components, supporting the anticipated Bragg filtering mechanism and envisioning the corresponding grating periods.

Rapid synthesis of nanomaterials by solvent-free laser irradiation for energy storage and conversion

Nanomaterials synthesized through laser irradiation have numerous applications in the field of energy storage and conversion. Conventional methods for fabricating nanomaterials often involve extended reaction times, making them susceptible to issues such as reproducibility, impurities, and inhomogeneity. To address these issues, a novel strategy of synthesizing nanomaterials via solvent-free laser irradiation in the gas phase is proposed as a potential solution. This innovative strategy offers ultrafast heating and cooling processes compared to conventional time-consuming methods, resulting in the formation of homogeneous nanosystems within femto- to nanosecond timeframes. The focused laser beam induces rapid photothermal and photochemical effects in either air or an inert gas atmosphere, enabling the rapid production of nanomaterials with precise control over geometry, chemistry, crystallinity, and defect density by adjusting processing conditions and sintering mediums. This review provides insights into the rapid solvent-free laser-assisted synthesis of nanomaterials using natural carbon-based materials, polymers, metal–organic frameworks, and inorganic species in both air and inert atmospheres. The introduction of photo-irradiation across a wide range of precursors facilitates phase transitions and surface functionalization in the resulting nanoproducts. We also discuss the effects of altering laser wavelengths, pulse widths, fluences, and repetition rates on both surface and bulk properties of the final products. Finally, we explore the applications of laser-induced nanomaterials in areas such as rechargeable batteries, supercapacitors, solar cells, and catalysis.

Design and develop an optical setup related to the pump-probe technique for spectroscopic study

In this research, an optical system using Pump-Probe technology was designed to study the effect of changing the Frequency values, integration time, delay time, and laser pulse width on the pumping pulse energy on an arbitrary laser dye material with an absorption coefficient of about 650 nm. we found that decreasing the pumping time to 10% of the pulse time is not suitable for the pump-probe technique because there is no resonance between the pumping time and the detector response to the source used. Also, we indicate that increasing the pumping time to 20% of the pulse time results in the highest possible detector response at an integration time 150 μs in the pump-probe technique. therefore, we noted that the detector response becomes more suitable for working in the pump-probe technique as the pumping time increases, as well as the efficiency of the detector, which increases significantly as the pumping time increases, as well as the integration time for the same delay time, it is more stable at 20% pumping time and collection time 150 μs at a delay time of 12.4 ns.

Laser-induced localized and maskless electrodeposition of micro-copper structure on silicon surface: Simulation and experimental study

The simulation and experimental study of laser-induced localized and maskless electrodeposition of micro-copper (Cu) structures on p-type silicon (Si) surface is investigated. Firstly, calculations of the internal temperature field and free electron density distribution within Si under nanosecond laser irradiation were carried out, to demonstrate the selective enhancing effect of laser irradiation on electrical conductivity via the thermal and photoconductive manner. Secondly, experimental tests of the laser-induced electrodeposition of micro-wires, regional coatings and complicated patterns on Si surface without mask were performed successively, to illustrate the effectiveness of the proposed method. The experimental results indicate that laser pulse width and scanning space significantly affect the quality of the deposited layer. Specifically, dense and flat micro wires can be achieved when the laser pulse width is 100 ns, which is associated with a width of about 71.7 μm and thickness of around 10.9 μm. In addition, the laser scanning space should be well optimized to balance the uniformity of the regional coating and the stray deposition near the edge. Finally, the reduction of Cu2+ and deposition of Cu atom at Si surface were discussed, as well as the development of transitional layer, to supply an in-depth analysis of the electrodeposition mechanism.

Determinants in laser-assisted deformed α decay

Laser manipulation of nuclear decay has extremely promising applications. In this study, cutting-edge Gaussian lasers were combined with the latest data on α decay to thoroughly investigate the factors that impact the penetration probability in laser-assisted α decay of nuclei, while considering the deformation of the nucleus. Our calculations reveal that using state-of-the-art laser fields can marginally alter the half-life of α decay by affecting the penetration probability within a narrow range. Moreover, our findings demonstrate two key points: (1) By deriving an analytical formula for the rate of change of the α decay penetration probability in an ultra-intense laser field, we unveil the negative correlation between the α decay energy and the rate of change of the α decay penetration probability. (2) We attribute the wavelength as the determinant of the effect of the average rate of change of the penetration probability, which we explain by reconstructing the laser pulse width and wavelength. This research offers a rapid method to estimate the rate of change of the α-decay penetration probability and serves as a valuable reference for future experimental investigations of laser-nuclear interactions.

Highly Efficient O-Band Rectangular Pulse Emission in a Figure-of-Nine Bismuth-Doped Fiber Laser

Highly efficient rectangular pulse emission is significant in high energy O-band applications due to the zero dispersion of standard telecom optical fiber in the second telecommunication window. The rectangular pulse emission offers the peak power clamping, which avoids wave-breaking and maintains the fundamental repetition frequency with arbitrarily widened temporal pulse width of ultrafast laser at high pump powers. The current technology in the O-band rectangular pulse emission achieves the maximum pulse energy of ∼30 nJ with an efficiency of ∼1.06%. Here, we fabricated a single-mode bismuth-doped phosphosilicate optical fiber by the modified chemical vapour deposition technique. The Bi-doped phosphosilicate optical fiber was characterized by a peak absorption of ∼0.6 dB/m at 1250 nm and a high gain coefficient of ∼0.22 dB/m at 1320 nm. These parameters contribute to the generation of rectangular pulse with a pump power threshold of ∼227.7 mW in a figure-of-nine laser cavity. The maximum pulse energy was achieved as ∼197.7 nJ, whereas the laser efficiency is ∼14.3%. We presented an O-band rectangular pulse emission with the highest pulse energy and efficiency as compared to previous studies, whilst its all-fiber laser setup is robust and feasible for high pulse energy applications.

Study of the TBC delamination in nanosecond laser percussion drilling of inclined film cooling holes

To protect superalloys under extremely high temperatures in aero-engine core components, thermal barrier coatings (TBC) are sprayed on the material surface and thousands of film cooling holes are drilled which produce a cooling air film. A large proportion of these holes must be drilled at inclined angles relative to the surface in order to provide optimal cooling effects. Laser drilling has been widely applied in the industrial fabrication of film cooling holes due to its high precision, high efficiency, flexibility in drilling angle, and ability to drill all kinds of materials. In particular, nanosecond lasers have attracted lots of interest because they can achieve a good balance between drilling quality and efficiency. However, TBC is prone to delaminate during laser drilling, which severely reduces the lifetime of aero-engine components. In this study, we investigate TBC delamination in nanosecond laser percussion drilling of inclined film cooling holes in TBC-coated cobalt-based superalloy. It was found that the leading edges of the inclined holes suffer from more severe TBC delamination than the trailing edges. By studying the effects of laser focus position, pulse width, pulse energy, repetition rate and average power, we found that faster hole breakthrough and less heat accumulation were essential for the reduction of TBC delamination. Through multi-physical numerical simulations, it was demonstrated that the asymmetric heat transfer effect in laser inclined drilling causes much larger interfacial thermal stress on the leading edge than the trailing edge, qualitatively explaining our experimental observations. The results of this study contribute to the understanding of TBC delamination in laser drilling of inclined film cooling holes.

Probing exciton dynamics with spectral selectivity through the use of quantum entangled photons.

Quantum light is increasingly recognized as a promising resource for developing optical measurement techniques. Particular attention has been paid to enhancing the precision of the measurements beyond classical techniques by using nonclassical correlations between quantum entangled photons. Recent advances in the quantum optics technology have made it possible to manipulate spectral and temporal properties of entangled photons, and photon correlations can facilitate the extraction of matter information with relatively simple optical systems compared to conventional schemes. In these respects, the applications of entangled photons to time-resolved spectroscopy can open new avenues for unambiguously extracting information on dynamical processes in complex molecular and materials systems. Here, we propose time-resolved spectroscopy in which specific signal contributions are selectively enhanced by harnessing nonclassical correlations of entangled photons. The entanglement time characterizes the mutual delay between an entangled twin and determines the spectral distribution of photon correlations. The entanglement time plays a dual role as the knob for controlling the accessible time region of dynamical processes and the degrees of spectral selectivity. In this sense, the role of the entanglement time is substantially equivalent to the temporal width of the classical laser pulse. The results demonstrate that the application of quantum entangled photons to time-resolved spectroscopy leads to monitoring dynamical processes in complex molecular and materials systems by selectively extracting desired signal contributions from congested spectra. We anticipate that more elaborately engineered photon states would broaden the availability of quantum light spectroscopy.

Optimization of extreme ultra-violet light emitted from the CO2 laser-irradiated tin plasmas using 2D radiation hydrodynamic simulations.

We studied Extreme Ultra-Violet (EUV) emission characteristics of the 13.5 nm wavelength from CO2 laser-irradiated pre-formed tin plasmas using 2D radiation hydrodynamic simulations. Our results indicate that when a CO2 laser irradiates pre-formed tin plasma, the heated plasma expands towards the surrounding plasma, steepening the density at the ablation front and lowering the density near the laser axis due to the transverse motion of the plasma. Consequently, the laser absorption fraction decreases, and the contribution to EUV output from the ablation front becomes dominant over that from the low-density plasmas. We estimated that an EUV conversion efficiency of 10% from laser to EUV emission could be achieved with a larger laser spot size, shortened laser pulse width, and longer pre-formed plasma density scale length. Our results offer one optimizing solution to achieve an efficient and powerful EUV light source for the next-generation semiconductors.

Optimizing process for pulsed laser additive manufacturing of nickel-based single crystal superalloy

The relationship between pulsed laser processing parameters and epitaxial growth of alloy is essential to additive manufacturing technology in repairing and manufacturing nickel-based single crystal (SX) superalloys. In this paper, orthogonal experiments of Laser Direct Energy Deposition (DED-L) process have been designed to optimize the process for the epitaxial growth of the SX superalloy. The relationship between process parameters and epitaxial growth of SX superalloy is established in a radar map, which shows that low laser power, pulse width and powder feeding rate help epitaxial growth in the DED-L process. It is implied that increasing the powder feeding rate value in the process range decreases the epitaxial growth rate of the molten pool and increases manufacturing efficiency. The size of the cladding layer width is greatly influenced by laser power (reached 44%) and pulse width (reached 38%). The deposited heigh of the cladding layer is mainly influenced by pulse width (reached 45%) and powder feeding rate (reached 42%). The process parameters have a similar level (approximately 33%) of influence on the powder using efficiency.

Ultrafast photoacoustic cavitation pumped by picosecond laser for high-efficient and long-term shockwave theranostics

Photoacoustic (PA) theranostics is a new emerging field that uniquely combines diagnosis and treatment in one modality. However, its current status is compromised by the indispensable dependence on nonreversible phase-change nanoprobes that provides one-time-only action. Here, we demonstrate a picosecond-laser-pumped ultrafast PA cavitation technique for highly efficient shockwave theranostics, guaranteeing sustained PA cavitation by using non-phase-change nanoprobes. Theoretical simulations validate that, when compressing the excitation laser pulse width to hundred-picosecond, the thermal confinement effects of a conventional nanoprobe will induce transient heating of the extremely thin surrounding liquid layer of the nanoprobes beyond its cavitation point in a localized area at nanoscale, resulting in intense cavitation and PA shockwaves by the environment rather than the nanoprobes. Both cellular and mouse model experiments have demonstrated the highly effective anti-tumor effects. This method provides a sustainable, reproducible, and highly effective strategy for PA theranostics, prefiguring great potential for the clinical applications.

Dissimilar laser welding of NiTi shape memory alloy to NiCr alloy

NiTi shape memory alloy (SMA) offers a wide range of industrial applications due to its shape memory effect and superelastic properties. In this study, a dissimilar joint between NiTi SMA and Ni–20Cr alloy was fabricated, and its microstructural and mechanical properties were analyzed. As a result of the formation of brittle intermetallic compounds (IMC), the tensile characteristics were reduced, and the hardness increased dramatically. Also, the effect of various laser pulse widths on bonding characteristics was examined, and as the pulse width increased, coarser IMCs were formed in the FZ. By performing post-weld heat treatment (PWHT) on the welded samples, the microstructure and mechanical properties of the FZ changed, and the NiTi intermetallic phase was produced. The results revealed that most IMCs generated had the same chemical composition ratio as Ni3Ti and Cr2Ti IMCs. In addition, after PWHT, the plateau region in the stress-strain curves was formed, while in the welded samples without PWHT, the joints failed at low stress and strain before forming the plateau region.

Development of Laser Cavitation Peening Using a Normal-Oscillation Nd:YAG Laser

The impact induced by cavitation bubble collapse can be utilized for mechanical surface treatment to improve fatigue properties of metals including additive manufactured metallic materials. A peening method using cavitation impact induced by a pulsed laser is called “laser cavitation peening (LCP)”. Normally, a Q-switched Nd:YAG laser, whose pulse width is a few nanoseconds, is used for LCP, which improves the fatigue strength. The problem with LCP is that the processing time is too slow. If a laser pulse whose pulse width is a few hundred microseconds can be utilized for LCP, the repetition frequency can be increased drastically using other types of laser systems such as a fiber laser. In the present paper, in order to reveal the possibility of LCP using a pulsed laser width of a few hundred microseconds, the use of LCP with a normal-oscillation Nd:YAG laser (pulse width ≈ 200 μs) was investigated. It is demonstrated that LCP with the normal-oscillation Nd:YAG laser produced curvature in an aluminum alloy plate. The shock pressure wave and impulsive vibration of the target surface at the first collapse of laser cavitation (LC), which was induced by the normal-oscillation Nd:YAG laser, was 3–4 times larger than those of laser ablation (LA).

Synergistic red dominancy over green upconversion studies in PbZrTiO3: Er3+/Yb3+ phosphor synthesized via two different modified technique and flexible thin-film thermometer demonstration on C1: PbZrTiO3 @PDMS substrates

Owing to its efficient wide range sensing using a noncontact mechanism with a decimal accuracy level, quick, non-invasive temperature sensors utilizing upconversion (UC) phosphor were examined. These sensors are perfect for cutting-edge applications such as measuring the intracellular temperature and identifying microelectronic issues. It may be possible to modify the performance of phosphor temperature sensors through nanoscale engineering. Despite were potential, it has been discovered that modern nanothermometers are ineffective in maintaining stability over a wide temperature range. Motivated by previous studies on efficient UC based solar cell demonstrations of Er3+/Yb3+: PbZrTiO3 (lead zirconate titanate) phosphors, the UC properties of Er3+/Yb3+: PbZrTiO3 for a wide range of temperature sensing and practical thermometer applications have been investigated. The UC emission properties of the Er3+/Yb3+: PbZrTiO3 phosphors synthesized via different routes, with the same dopant concentration, were compared. We have also investigated the formation of two different crystal symmetry, and an approach for the fine-tuning of the emission from the green to the red region upon changing the synthesis technique. The strategy of choosing an optimized synthesis route, based upon structural investigations, could be a way forward where dopant modification in phosphors is ruled out. Based on the UC optimization, the green and red dominant phosphors under 980 nm excitation with different pulse widths and power densities or at different temperatures were studied; the possible mechanisms were discussed in detail. The sensitivity of Er3+/Yb3+: PbZrTiO3 was independent of the pumping laser characteristics since it was essentially consistent when utilising both continuous wave and laser pulse width modulation or varying power densities. To assess the temperature of the microelectronic components, a flexible thin-film thermometer was made of Er3+/Yb3+: PbZrTiO3 on a polyDiMethylSiloxane substrate. This thermometer shows great repeatability and can measure the temperature of an electronic circuit board correctly. The findings suggested that the current non-contact UC temperature sensor might potentially replace conventional thermometers because of its steady green emission over a wide temperature range (313–673 K) and thermometric sensitivity.

Process Analysis and Topography Evaluation for Monocrystalline Silicon Laser Cutting-Off.

Due to the characteristics of high brittleness and low fracture toughness of monocrystalline silicon, its high precision and high-quality cutting have great challenges. Aiming at the urgent need of wafer cutting with high efficiency, this paper investigates the influence law of different laser processes on the size of the groove and the machining affected zone of laser cutting. The experimental results show that when laser cutting monocrystalline silicon, in addition to generating a groove, there will also be a machining affected zone on both sides of the groove and the size of both will directly affect the cutting quality. After wiping the thermal products generated by cutting on the material surface, the machining affected zone and the recast layer in the cutting seam can basically be eliminated to generate a wider cutting seam and the surface after wiping is basically the same as that before cutting. Increasing the laser cutting times will increase the width of the material's machining affected zone and the groove width after chip removal. When the cutting times are less than 80, increasing the cutting times will increase the groove width at the same time; but, after the cutting times exceed 80, the groove width abruptly decreases and then slowly increases. In addition, the lower the laser scanning speed, the larger the width of the material's machining affected zone and the width of the groove after chip removal. The increase in laser frequency will increase the crack width and the crack width after chip removal but decrease the machining affected zone width. The laser pulse width has a certain effect on the cutting quality but it does not show regularity. When the pulse width is 0.3 ns the cutting quality is the best and when the pulse width is 0.15 ns the cutting quality is the worst.

Study on the Duration of Laser-Induced Thin Film Plasma Flash

The accuracy of judging whether the film is damaged directly affects the accuracy of the measurement of the film laser damage threshold. When judging the film damage by the traditional plasma flash method, there is a problem of misjudgment caused by the failure to distinguish the film and air plasma flash. In order to eliminate misjudgment, the two flashes are accurately distinguished by the difference in the duration of the air and film plasma flash. This paper aims to obtain the theoretical and experimental values of the duration of the film plasma flash (tf) and analyze the factors affecting it. Firstly, taking single-layer hafnium oxide and aluminum oxide thin films as examples, when the wavelength of the incident laser is 1064 nm, the diameter of the laser focusing spot is 0.08 cm, the energy of the incident laser is 100 mJ, and the pulse width of incident laser is 10 ns, the tf of hafnium oxide, and aluminum oxide thin films are 542.7 and 299.6 ns, respectively. Secondly, the experimental study of tf was carried out. Through six experiments, the following results were obtained: (1) With the increase in incident laser energy, the tf of both films increases; (2) The tf of the hafnium oxide film is longer than that of the aluminum oxide film. (3) The experimental parameters are put into the calculation model, and the theoretical results are in good agreement with the experimental tf values. Finally, it is found that tf increases with the increase in incident laser energy and incident laser pulse width, and decreases with the increase in focusing spot diameter.

Reliability study on the half-cutting PERC solar cell and module

In the photovoltaic industry, there are three critical parameters such as module power, cost and reliability. For increasing module power, half-cutting technology on the cell is one of the technologies because this can reduce the heating power by reducing the current. Therefore, laser scribing and mechanical cleaving (LSMC) technology have been implemented. As a result, the power of the module did not show any loss during standard test conditions when electrical luminescence and powers were monitored for the laser dicing process. However, in field conditions, the cut side of the cells with the laser process can cause cell breakage by wind or snow if the side has cracks. And then these crack cells can finally cause module power loss. Therefore, in this study, the laser process quality of the cell has been investigated by microscope image and scanning electron microscopy with laser process parameters such as laser power, frequency, and pulse width. In addition, cell strength was also checked by the four points of bending force to find the optimized laser process condition. The module power loss was analyzed with a static mechanical load test (MLT), which can represent snow or wind effect in the field. Our analyses show a strong correlation between crack width by laser, cell bending force, and module power loss. This correlation can explain the module power loss estimation, which can affect the reliability in the field without making module-level tests for the first time. In addition, the encapsulant thickness combination test and the mid-rail effect were also presented to reduce the power loss. As a result, the module power loss reached -1.34%. Finally, this study can contribute to the better reliability of the big wafer size products with LSMC technology.

Modeling and Simulation of Fe-Doped GaN PCSS in High-Power Microwave

In this article, the characteristics of linear GaN photoconductive semiconductor switch (PCSS) in high-power microwaves are investigated by Silvaco TCAD (Technology Computer-Aided Design). By comparison of optical absorption efficiency among three types of PCSS structures, the optimized Fe-doped GaN PCSS is designed in a side-illuminated, vertical structure with a spot size of 1 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times$</tex-math> </inline-formula> 8 mm. The photocurrent of side-illuminated GaN vertical PCSS (vPCSS) begins to saturate at 1.65 mJ with the increase of applied optical energy. The average saturated switch resistance and electron concentration of vPCSS under a bias voltage of 5–20 kV are almost 8.2 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\pmb\Omega $</tex-math> </inline-formula> and 3.5 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times$</tex-math> </inline-formula> 10 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\text{14}}$</tex-math> </inline-formula> cm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{-\text{3}}$</tex-math> </inline-formula> , respectively. As the device is in a saturated photocurrent state, the peak photocurrent is a linear function of bias voltage. As the device is in an unsaturated photocurrent state, improving the light energy is more effective than the withstand voltage of the device to increase photocurrent. Due to the short carrier lifetime, the GaN vPCSS has the response capacity to a 50-ps pulsewidth laser. Based on side-illuminated GaN vPCSS at the bias field 200 kV/cm, a narrowband microwave with adjustable frequency (3.3–5 GHz) could be generated. The maximum output power reaches up to 1.3 kW. Effects of anti-reflective (AR) and reflective coatings on optical absorption are investigated. The photocurrent of vPCSS with both AR and reflective coatings increases by 77.2% as compared with normal vPCSS.